Deploying resource-intensive Video LLMs often relies on Split DNNs, yet this introduces a severe transmission bottleneck-intermediate embeddings 1 can be$26 \times$larger than original videos. Lossy compression is an effective solution to the I/O bottleneck in machine learning [1]. However, no compression solution exists to address the high dimensionality and unique layout of these embeddings.

Error-bounded lossy compressors have been developed for years to reduce the vast volumes of scientific data generated by high-performance computing (HPC) applications and advanced scientific instruments. While these compressors have been effective in mitigating the challenges posed by massive datasets, a significant gap remains in our understanding of the fundamental compressibility limits of scientific data–an issue that critically impacts the sustainable adoption and development of efficient lossy compression techniques in practice. Classical rate-distortion theory, established by Shannon, assumes stationary 1D sources with unconstrained coding–assumptions that do not hold for scientific datasets compressed under the tiling constraints imposed by modern parallel lossy compressors. This paper addresses this gap by developing a novel framework that characterizes compressibility limits for scientific datasets under realistic tiling constraints. The contribution is two-fold. First, we establish a tile-aware, finite-blocklength extension of rate–distortion theory that advances classical 1D asymptotic formulations into a rigorous framework for piecewise 2D Gaussian random fields. To our knowledge, this is the first framework to rigorously characterize lossy compressibility limits for scientific datasets and compressor, moving beyond classical asymptotic 1D source models. Second, we conduct a comprehensive validation of the proposed modeling framework using state-of-the-art error-bounded lossy compressors and diverse real-world HPC datasets, demonstrating that our theory accurately predicts rate-distortion trends and provides actionable insights for compressor design.

As high-performance computing shifts toward GPU-accelerated exascale systems, the exponential growth of scientific data poses severe challenges to both storage capacity and I/O bandwidth. While current GPU-based lossy compressors attempt to address this by porting CPU algorithms to the device, they rely heavily on block-wise spatial decomposition to fit GPU parallelism. This approach suffers from a fundamental locality barrier: by partitioning data into independent blocks, these methods fail to capture global correlations and fragment the unified data patterns required for effective coding, severely limiting compression ratios. In this paper, we propose TZ, a novel GPU-native error-bounded lossy compressor that breaks this ceiling by adopting global Tucker decomposition. By prioritizing global spectral energy compaction over local approximation, TZ naturally maximizes the compression potential for scientific datasets. To render this computationally intensive approach practical for high-throughput GPU workflows, we introduce a highly optimized adaptive randomized SVD engine. This design allows TZ to achieve the superior compression ratios of global spectral decomposition while maintaining competitive execution speeds. Furthermore, the global processing nature of TZ enables a unified quantization and coding scheme that eliminates block artifacts and metadata overhead. Evaluation on production-scale scientific datasets demonstrates that TZ achieves approximately 10 × higher compression ratios than state-of-the-art GPU compressors under the same error bound, while maintaining competitive, high-throughput performance.

Error-controlled lossy compressors have been widely used in scientific applications to reduce the unprecedented size of scientific data while keeping data distortion within a user-specified threshold. While they significantly mitigate the pressure for data storage and transmission, they prolong the time to access the data because decompression is required to transform the binary compressed data into meaningful floating-point numbers. This incurs noticeable overhead for common analytical operations on scientific data that extract or derive useful information, because the time cost of the operations could be much lower than that of decompression. In this work, we design an error-controlled lossy compression and analytical framework that features multi-stage decompression and homomorphic analytical operation algorithms on intermediate decompressed data for reduced data access latency. Our contributions are threefold. (1) We abstract a generic compression pipeline with partial decompression to multiple intermediate data representations and implement four instances based on state-of-the-art high-throughput scientific data compressors. (2) We carefully design homomorphic algorithms to enable direct operations on intermediate decompressed data for three types of analytical operations on scientific data. (3) We evaluate our approach using five real-world scientific datasets. Experimental evaluations demonstrate that our method achieves significant speedups when performing analytical operations on compressed scientific data across all three targeted analytical operation types.

Large language models (LLMs) are increasingly integrated into high-performance computing (HPC) workflows, accelerating scientific discovery through diverse perspectives such as code generation and domain-specific decision-making. Yet, how soft errors propagate and affect LLM inference remains largely unexplored. To bridge this gap, we present a comprehensive study on error propagation in LLM inference, enabled by our proposed LLMFI, a configurable and deterministic fault-injection framework. Using LLMFI, we systematically inject faults across three open-weighted LLMs and thirteen representative tasks, covering reasoning, multilingual, mathematical, and coding domains. In addition, we conduct fine-grained case studies that reveal critical vulnerability patterns. Overall, our study yields 17 takeaways that advance the understanding of error propagation in LLM inference and introduces four low-overhead directions to improve reliability through software-only modification, offering practical guidance for future error detection and mitigation.

Particle-based simulations and point-cloud applications generate massive, irregular datasets that challenge storage, I/O, and real-time analytics. Traditional compression techniques struggle with irregular particle distributions and GPU architectural constraints, often resulting in limited throughput and suboptimal compression ratios. In this paper, we present GPZ, a high-performance, error-bounded lossy compressor designed specifically for large-scale particle data on modern GPUs. GPZ employs a novel four-stage parallel pipeline that synergistically balances high compression efficiency with the architectural demands of massively parallel hardware. We introduce a suite of targeted optimizations for computation, memory access, and GPU occupancy that enable GPZ to achieve near-hardware-limit throughput. We conduct an extensive evaluation on three distinct GPU architectures (workstation, data center, and edge) using six large-scale, real-world scientific datasets from four distinct domains. The results demonstrate that GPZ consistently and significantly outperforms four state-of-the-art GPU compressors, delivering up to 8x higher end-to-end throughput while achieving superior compression ratios and data quality.

Tackling temporal path problems in temporal graphs is essential for time-sensitive applications. Although many solutions have been proposed to handle temporal path problems, due to the intrinsic time constraints, these solutions require the vertices of the temporal graph to be sequentially handled along the time-dependent chains (i.e., the temporal dependencies between these vertices) to form the temporal path. This sequential temporal nature poses the challenges of poor parallelism and slow convergence speed, preventing existing solutions from fully leveraging the massive parallelism and high internal bandwidth of GPU to handle temporal path problems. To overcome these challenges, this paper proposes TempGraph, an efficient chain-driven GPU-based temporal graph computing framework. Specifically, it transforms the temporal graph into a set of disjoint time-dependent chains that can elegantly expose the temporal dependency between the vertices while facilitating the fast path exploration along these chains over GPU. Furthermore, TempGraph employs a novel Generate-Activate-Compute execution model to decouple the temporal dependency between different chains through maintaining a set of shortcuts for them, which enables multiple chains to be concurrently handled by massive GPU threads, achieving fast convergence speed and high parallelism on the GPU. Experiments on an A100 GPU show that TempGraph outperforms the state-of-the-art GPU-based solutions by 3.0-16.2×. Besides, TempGraph on an A100 GPU gains 33.9-368.9× speedups compared to the cutting-edge CPU-based system TeGraph on a 128-core CPU machine.

Compression is a crucial solution for data reduction in modern scientific applications due to the exponential growth of data from simulations, experiments, and observations. Compression with progressive retrieval capability allows users to quickly access coarse approximations of data and then incrementally refine these approximations to higher fidelity. Existing progressive compression solutions suffer from low reduction ratios or high operation costs, effectively undermining the approach's benefits. In this paper, we propose our interpolation-based progressive lossy compression solution that has both high reduction ratios and low operation costs. The interpolation-based algorithm has been verified as one of the best for scientific data reduction, but previously, no effort exists to make it support progressive retrieval. Our contributions are threefold: (1) We thoroughly analyze the error characteristics of the interpolation algorithm and propose our solution, IPComp, with multi-level bitplane and predictive coding. (2) We derive optimized strategies toward minimum data retrieval under different fidelity levels indicated by users through error bounds and bitrates. (3) We evaluate the proposed solution using six real-world datasets from four diverse domains. Experimental results demonstrate our solution archives up to 487% higher compression ratios and 698% faster speed than other state-of-the-art progressive compressors, and reduces the data volume for retrieval by up to 83% compared to baselines under the same error bound, and reduces the error by up to 99% under the same bitrate.

Graph propagation algorithms such as PageRank and its variants are widely used in modern applications such as ranking webpages, spam detection, and recommender systems. To cope with the web-scale graphs in these applications, many distributed vertex-centric systems, a.k.a. Pregel-like systems, have been proposed that can be used to parallelize the iterative graph propagation algorithms. In this work, we propose a message compression framework for Pregel-like systems, called CompreGel, which accelerates graph propagation algorithms by significantly reducing the communication cost of message passing. In a Pregel-like system, messages are streams of key-value pairs, where keys (resp. values) are the IDs of the target vertices (resp. vertex values such as PageRank values for dispersion). Our framework compresses the keys and values separately to maximize the compression power. Specifically, CompreGel employs the lossless bitmap compression for keys by utilizing an ID renumbering technique, and it employs the popular error-bounded lossy compressor SZ for values. Moreover, we theoretically analyze how to set the error bound parameter of SZ properly to bound the accumulative error of vertex values across iterations of graph propagation. Extensive experiments show that CompreGel can improve job efficiency by up to 10 × with a 200 × message compression ratio, while achieving comparable accuracy to a Pregel-like system without message compression.

In the exascale computing era, collective communication has emerged as a significant bottleneck for GPU-based applications, as network bandwidth lags behind rapid GPU advancements.While traditional GPU-aware approaches employ error-bounded lossy compression to mitigate this issue, they incur substantial decompression-operation-compression (DOC) overhead.To overcome these limitations, we introduce ghZCCL, a first-ever GPU-aware homomorphic compression-accelerated collective communications library that enables direct computation and communication on compressed data, eliminating the DOC workflow.We design the first GPU homomorphic compressor, surpassing the fastest existing GPU lossy compressor, cuSZp2, by 3.47-3.89×for DOC workloads.We also propose co-design strategies to further optimize GPU-aware collective communications with homomorphic compression.Experiments on up to 512 NVIDIA A100 GPUs show that ghZCCL outperforms three state-of-the-art communication libraries-gZCCL, NCCL, and Cray MPI-by achieving speedups of up to 2.29×, 5.81×, and 188×, respectively, while maintaining high data accuracy.

Federated Learning (FL) is a scalable and privacy-preserving paradigm well-suited for edge computing. Real-world FL deployments face substantial systems challenges such as compute variability and communication delays, motivating researchers to leverage simulation before real deployment. Most existing FL simulators, however, struggle to scale efficiently and incur long runtimes even for small workloads. To address this, we present FedDES, a high-fidelity, framework-agnostic discrete-event simulation platform that accurately models the runtime behavior of FL systems, including client training, communication overhead, network dynamics, and aggregation strategies. FedDES supports flexible configurations and diverse aggregation approaches, achieving simulation error within 2% of real deployments and delivering over 1000× speedup compared to prior tools. Large-scale experiments with up to 131,072 clients further show that the aggregation strategy critically affects performance, especially under heterogeneous and variable network conditions typical of edge environments.

High-performance computing (HPC) systems generate massive scientific datasets, often stored in remote data repositories. Limited bandwidth and resource-constrained endpoints pose challenges for efficient large data transfer. Error-bounded lossy compression addresses this by reducing data sizes (higher bit-rates) while controlling distortion. However, different compressors exhibit distinct rate-distortion behaviors even under the same error bounds. Thus, selecting an optimal compressor before transfer is essential to meet endpoint-specific requirements e.g., maximizing data reduction at a fixed distortion. Existing trial-and-error approaches require multiple costly full-scale compression runs to reach at target requirements, making them impractical for such online use. To address this, we propose OptRD, a compressor-agnostic framework that efficiently models rate-distortion trade-offs across multiple lossy compressors by analyzing spatial data traits at reduced resolutions. Evaluated using 3 state-of-the-art lossy compressors on 30 scientific datasets from 4 HPC applications, OPTRD incurs only$\sim 5 \%$average estimation error and achieves over$100 \times$runtime speedup compared to trial-and-error methods, significantly improving optimal compressor selection during such data transfer use cases.

High-throughput data compression is increasingly important for large scientific projects. This paper presents PFPL, a lossy floating-point data compressor with guaranteed error bounds that is fully compatible between CPUs and GPUs. Despite this compatibility, PFPL delivers some of the highest compression and decompression speeds and compression ratios on both single- and double-precision data. For example, using an absolute error bound of$1 \mathrm{E}-3$, it yields a single-precision compression throughput on the SDRBench inputs of$5 \text{GB} / \mathrm{s}$on a Ryzen 2950X CPU and 423 GB/s on an RTX 4090 GPU. This is at least 4.6 times higher than the throughput of seven leading compressors on both devices. Moreover, PFPL's compression ratio is higher than that of all tested GPU codes.

Large-scale scientific simulations produce unprecedented amounts of data using high-performance computing systems, leading to severe problems in data storage, I/O, and communication. To address the data movement challenge, errorcontrolled lossy compression has been proposed to significantly reduce the data size while retaining the data quality. Recently, interpolation-based compressors, including MGARD, SZ3, QoZ, and HPEZ, have stood out due to their efficiency in obtaining relatively high compression ratios with decent compression and decompression throughput. Nevertheless, these methods focus on data decorrelation in the compression pipeline yet overlook the correlation of the quantization indices generated after decorrelation. In this paper, we develop a generic framework that can use the correlation of quantization indices to significantly improve the compression ratios for state-of-the-art interpolation-based error-bounded lossy compressors. Our contributions are threefold: (1) We carefully characterized the quantization index array produced by the interpolation-based compressors and identified the unused correlation; (2) We designed a generic quantization index prediction method to exploit such correlation, which leads to improved compression ratio with only minor degradation in throughput; (3) We integrate our method into 4 state-of-theart interpolation-based compressors and evaluate them using 5 real-world datasets. Experimental results demonstrate that the proposed method improves the compression ratios of the base compressors by up to 95% while keeping the same quality. It also leads to 16% improvement in end-to-end data transfer performance under a parallel setting.

Compression ratio estimation is an important optimization of I/O workflows processing terabytes of data. Applications such as compression auto-tuning or lossy compressor selection require a high-throughput, accurate estimation to be fast. Prior works that utilize sampling are fast but inaccurate, while approaches that do not use sampling are accurate but slow. We present a novel, lightweight sampling technique that excels in speed and accuracy, by leveraging both statistical and spatial properties of dataset samples. Through a comprehensive sensitivity analysis we show that there is no one-size-fits-all sampling strategy because of differences in compression principles, and accounting for these differences has a direct impact on overall prediction accuracy in the methods that use these predictions. Our estimation technique demonstrates superior ($1.36 \times$to$11 \times$) prediction accuracy compared to existing sampling methods while significantly improving data throughput by$3.46 \times$compared to non-sampling approaches.

Cerebras system has demonstrated immense potential across various scientific domains. However, modern scientific simulations frequently generate vast volumes of data in a short time, leading to bottlenecks in runtime performance and memory footprint. While an ultra-fast error-bounded lossy compressor can mitigate such limitations with high compression ratios and guaranteed data quality, deploying it into Cerebras dataflow architecture poses significant difficulties. Specifically, Cerebras faces memory challenges, such as the absence of shared memory and limited local memory, alongside computational challenges, including specialized parallelism and sensitivity to imbalanced workloads. In this work, we propose CERESZII, an error-bounded lossy compressor that computes within Cerebras system. CereSZ-II addresses these challenges with a carefully optimized four-stage compression workflow, consisting of Pre-quantization, Lightweight Prediction, Fixed-size Huffman Encoding, and Spatial-aware Offset Computation, ensuring both memory efficiency and computational balance. Evaluation of several real-world scientific datasets shows that CERESZ-II achieves over 800 GB/s throughput, delivering high compression ratios and reliable reconstructed data quality.

Modern scientific simulations generate massive volumes of data, creating significant challenges for I/O and storage systems. Error-bounded lossy compression (EBLC) offers a solution by reducing data set sizes while preserving data quality within user-specified limits. This study provides the first comprehensive energy characterization of state-of-the-art EBLC algorithms-SZ2, SZ3, ZFP, QoZ, and SZx-across various scientific data sets, CPU generations, and parallel/serial modes. We analyze the energy consumption patterns of compression and decompression operations, as well as the energy trade-offs in data I/O scenarios. Our work demonstrates the relationships between compression ratios, runtime, energy efficiency, and data quality, highlighting the importance of considering compressors and error bounds for specific use cases. We demonstrate that EBLC can significantly reduce I/O energy consumption, with savings of up to two orders of magnitude compared to uncompressed I/O for large data sets. In multi-node HPC environments, we observe energy reductions of approximately 25 % when using EBLC. We also show that EBLC can achieve compression ratios of$10-100 \times$, potentially reducing storage device requirements by nearly two orders of magnitude. This work provides a framework for system operators and computational scientists to make informed decisions about implementing EBLC for energy-efficient data management in HPC environments.

Today's scientific applications are producing vast amounts of data with cutting-edge high-performance computing systems and high-resolution instruments, causing severe problems in data transmission and storage. While error-controlled data compression is regarded as a direct way to solve the problem, most existing compressors are designed for data from structured meshes. In this work, we propose a generic framework to enable efficient error-controlled compression for scientific data from unstructured meshes. The contributions are four-fold: (1) We design a prediction-based framework with additional preprocessing stages to better incorporate mesh information. (2) We propose three families of prediction methods for unstructured meshes and integrate them into the framework, which yields high prediction accuracy and thus significantly improves the compression ratios and quality. (3) We enhance our framework by enabling invalid node processing and feature preservation. (4) We evaluate our approaches using five datasets from real-world applications and compare them with state-of-the-art error-controlled lossy compressors. Experiments demonstrate that the proposed compression methods deliver up to$26.36 \times, 8.24 \times$, and$2.56 \times$compression ratios over existing compressors under the same error bound, Peak Signal-to-Noise Ratios, and critical point preservation levels, respectively. This leads to$1.63 \times$performance speedup in the end-to-end data transfer on Globus.

Second-order optimization methods have been developed to enhance convergence and generalization in deep neural network (DNN) training compared to first-order methods like Stochastic Gradient Descent (SGD). However, these methods face challenges in distributed settings due to high communication overhead. Gradient compression, a technique commonly used to accelerate communication for first-order approaches, often results in low communication reduction ratios, decreased model accuracy, and/or high compression overhead when applied to second-order methods. To address these limitations, we introduce a novel gradient compression method for second-order optimizers called COMPSO. This method effectively reduces communication costs while preserving the advantages of second-order optimization. COMPSO employs stochastic rounding to maintain accuracy and filters out minor gradients to improve compression ratios. Additionally, we develop GPU optimizations to minimize compression overhead and performance modeling to ensure end-to-end performance gains across various systems. Evaluation of COMPSO on different DNN models shows that it achieves a compression ratio of 22.1×, reduces communication time by 14.2×, and improves overall performance by 1.9×, all without any drop in model accuracy.

GPU-based fast Fourier transform (FFT) is extremely important for scientific computing and signal processing. However, we find the inefficiency of existing FFT libraries and the absence of fault tolerance against soft error. To address these issues, we introduce TurboFFT, a new FFT prototype co-designed for high performance and online fault tolerance. For FFT, we propose an architecture-aware, padding-free, and template-based prototype to maximize hardware resource utilization, achieving a competitive or superior performance compared to the state-of-the-art closed-source library, cuFFT. For fault tolerance, we 1) explore algorithm-based fault tolerance (ABFT) at the thread and threadblock levels to reduce additional memory footprint, 2) address the error propagation by introducing a two-side ABFT with location encoding, and 3) further modify the threadblock-level FFT from 1-transaction to multi-transaction in order to bring more parallelism for ABFT. Our two-side strategy enables online correction without additional global memory while our multi-transaction design averages the expensive threadblock-level reduction in ABFT with zero additional operations. Experimental results on an NVIDIA A100 server GPU and a Tesla Turing T4 GPU demonstrate that TurboFFT without fault tolerance is comparable to or up to 300% faster than cuFFT and outperforms VkFFT. TurboFFT with fault tolerance maintains an overhead of 7% to 15%, even under tens of error injections per minute for both FP32 and FP64.

Over the last nearly 20 years, lossy compression has become an essential aspect of HPC applications’ data pipelines, allowing them to overcome limitations in storage capacity and bandwidth and, in some cases, increase computational throughput and capacity. However, with the adoption of lossy compression comes the requirement to assess and control the impact lossy compression has on scientific outcomes. In this work, we take a major step forward in describing the state of practice and by characterizing workloads. We examine applications’ needs and compressors’ capabilities across 9 different supercomputing application domains. We present 24 takeaways that provide best practices for applications, operational impacts for facilities achieving compressed data, and gaps in application needs not addressed by production compressors that point towards opportunities for future compression research.

This work proposes VGC, a versatile and ultra-fast GPU lossy compression framework designed to address the growing data challenges in high-performance computing (HPC). VGC captures dimension information in scientific data and supports three compression algorithms, achieving high compression ratios across diverse HPC domains. Built with a highly optimized GPU kernel, VGC delivers state-of-the-art throughput with error control. In addition to compression ratio and speed, VGC supports two distinctive modes that enhance its versatility. Memory-efficient Compression uses a kernel fission design to compute compressed size, allocate only the required GPU memory, and compress data without waste, effectively reducing memory footprint. Selective Decompression introduces an early stopping mechanism that enables direct access to regions of interest without decompressing the entire dataset.

Light source facilities, which generate X-rays for probing microstructures and dynamic processes, produce intense data streams, reaching up to 250 GB/s and projected to exceed 1 TB/s by the end of this decade. Managing such massive data poses critical challenges due to limited local processing capacity and bandwidth constraints when offloading data to HPC systems. To address these challenges, we propose lsCOMP, a GPU compressor that operates within a single kernel. lsCOMP supports both lossless and configurable lossy compression, ensuring high compression ratios and preserved data quality across diverse light source applications. On a single NVIDIA A100 GPU, lsCOMP achieves compression throughputs of 380.89 to 509.21 GB/s in lossless mode, delivering up to 20 times higher performance than industry-leading GPU compressors while achieving superior compression ratios. In lossy modes, lsCOMP further improves throughput and ratios significantly. Additionally, lsCOMP demonstrates versatile performance across various integer datasets and supports TB/s-level random access throughput.

As high-performance computing architectures evolve, more scientific computing workflows are being deployed on advanced computing platforms such as GPUs. These workflows can produce raw data at extremely high throughputs, requiring urgent high-ratio and low-latency error-bounded data compression solutions. In this paper, we propose cuSZ-Hi, an optimized high-ratio GPU-based scientific error-bounded lossy compressor with a flexible, domain-irrelevant, and fully open-source framework design. Our novel contributions are: 1) We maximally optimize the parallelized interpolation-based data prediction scheme on GPUs, enabling the full functionalities of interpolation-based scientific data prediction that are adaptive to diverse data characteristics; 2) We thoroughly explore and investigate lossless data encoding techniques, then craft and incorporate the best-fit lossless encoding pipelines for maximizing the compression ratio of cuSZ-Hi; 3) We systematically evaluate cuSZ-Hi on benchmarking datasets together with representative baselines. Compared to existing state-of-the-art scientific lossy compressors, with comparative or better throughput than existing high-ratio scientific error-bounded lossy compressors on GPUs, cuSZ-Hi can achieve up to 249% compression ratio improvement under the same error bound, and up to 215% compression ratio improvement under the same decompression data PSNR.

Many scientific applications opt for particles instead of meshes as their basic primitives to model complex systems composed of billions of discrete entities. Such applications span a diverse array of scientific domains, including molecular dynamics, cosmology, computational fluid dynamics, and geology. The scale of the particles in those scientific applications increases substantially thanks to the ever-increasing computational power in high-performance computing (HPC) platforms. However, the actual gains from such increases are often undercut by obstacles in data management systems related to data storage, transfer, and processing. Lossy compression has been widely recognized as a promising solution to enhance scientific data management systems regarding such challenges, although most existing compression solutions are tailored for Cartesian grids and thus have sub-optimal results on discrete particle data. In this paper, we introduce LCP, an innovative lossy compressor designed for particle datasets, offering superior compression quality and higher speed than existing compression solutions. Specifically, our contribution is threefold. (1) We propose LCP-S, an error-bound aware block-wise spatial compressor to efficiently reduce particle data size while satisfying the pre-defined error criteria. This approach is universally applicable to particle data across various domains, eliminating the need for reliance on specific application domain characteristics. (2) We develop LCP, a hybrid compression solution for multi-frame particle data, featuring dynamic method selection and parameter optimization. It aims to maximize compression effectiveness while preserving data quality as much as possible by utilizing both spatial and temporal domains. (3) We evaluate our solution alongside eight state-of-the-art alternatives on eight real-world particle datasets from seven distinct domains. The results demonstrate that our solution achieves up to 104% improvement in compression ratios and up to 593% increase in speed compared to the second-best option, under the same error criteria.

Error-bounded lossy compression has been widely adopted in many scientific domains because it can address the challenges in storing, transferring, and analyzing unprecedented amounts of scientific data. However, general error-bounded lossy compressors may fail to meet additional quality requirements for downstream analysis, a.k.a. Quantities of Interest (QoIs). This may lead to uncertainties and even misinterpretations in scientific discoveries, significantly limiting the use of lossy compression in practice. In this paper, we propose QPET, a novel, versatile, and portable framework for QoI-preserving error-bounded lossy compression, which overcomes the challenges of modeling diverse QoIs by leveraging numerical strategies. QPET features (1) high portability to multiple existing lossy compressors, (2) versatile preservation to most differentiable univariate and multivariate QoIs, and (3) significant compression improvements in QoI-preservation tasks. Experiments with six real-world datasets demonstrate that integrating QPET into state-of-the-art error-bounded lossy compressors can gain 2x to 10x compression speedups of existing QoI-preserving error-bounded lossy compression solutions, up to 1000% compression ratio improvements to general-purpose compressors, and up to 133% compression ratio improvements to existing QoI-integrated scientific compressors.

Large volumes of data generated by scientific simulations, genome sequencing, and other applications need to be moved among clusters for data collection/analysis. Data compression techniques have effectively reduced data storage and transfer costs. However, users' requirements on interactively controlling both data quality and compression ratios are non-trivial to fulfill. We propose a novel Compression-as-a-Service (CaaS) platform called Ocelot with four important contributions: (1) It offers real-time visualization, interactive compression, and transfer of scientific datasets. (2) It incorporates new strategies for compressing diverse types of datasets more effectively than traditional methods. (3) It provides an effective method for estimating the compression ratio and execution time of compression tasks. (4) Experiments on multiple real-world datasets on geographically distributed computers show that Ocelot can significantly improve data transfer efficiency with a performance gain of more than 10x in computing clusters with relatively slow networks.

Cross-Silo federated learning systems have been identified as an efficient approach to scaling DNN training across geographically-distributed data silos to preserve the privacy of the training data. Communication efficiency and fairness are two major issues that need to be both satisfied when federated learning systems are deployed in practice. Simultaneously guaranteeing both of them, however, is exceptionally difficult because simply combining communication reduction and fairness optimization approaches often causes non-converged training or drastic accuracy degradation. To bridge this gap, we proposeFedEFsz. On the one hand, it integrates the state-of-the-art error-bounded lossy compressor SZ3 into cross-silo federated learning systems to significantly reduce communication traffic during the training. On the other hand, it achieves a high fairness (i.e., rather consistent model accuracy and performance across different clients) through a carefully designed heuristic algorithm that can tune the error-bound of SZ3 for different clients during the training. Extensive experimental results based on a GPU cluster with 65 GPU cards show thatFedEFszimproves the fairness across different benchmarks by up to$60.88\%$and meanwhile reduces the communication traffic by up to$315\times$.

Cross-Silo federated learning is widely used for scaling deep neural network (DNN) training over data silos from different locations worldwide while guaranteeing data privacy. Communication has been identified as the main bottleneck when training large-scale models due to large-volume model parameters and gradient transmission across public networks with limited bandwidth. Most previous works focus on gradient compression, while limited work tries to compress parameters that can not be ignored and extremely affect communication performance during the training. To bridge this gap, we proposeFedCSpc: an efficient cross-silo federated learning system with an XAI-driven adaptive parameter compression strategy for large-scale model training. Our work substantially differs from existing gradient compression techniques due to the distinct data features of gradient and parameter. The key contributions of this paper are fourfold. (1) Our designedFedCSpcproposes to compress the parameter during the training using the state-of-the-art error-bounded lossy compressor – SZ3. (2) We develop an adaptive compression error bound adjustment algorithm to guarantee the model accuracy effectively. (3) We exploit an efficient approach to utilize the idle CPU resources of clients to compress the parameters. (4) We perform a comprehensive evaluation with a wide range of models and benchmarks on a GPU cluster with 65 GPUs. Results show thatFedCSpccan achieve the same model accuracy as FedAvg while reducing the data volume of parameters and gradients in communication by up to 7.39× and 288×, respectively. With 32 clients on a 4Gb size model,FedCSpcsignificantly outperforms FedAvg in wall-clock time in the emulated WAN environment (at the bandwidth of 1 Gbps or lower without loss of generality).

As scientific simulations generate increasingly large datasets, efficient data compression becomes essential to mitigate storage and transmission challenges. Error-bounded Lossy compression algorithms reduce data volume at the expense of data fidelity. However, the evaluation of compressed data quality can be resource-intensive and time-consuming. This paper proposes a surrogate-based framework to predict key compression quality assessment metrics, allowing users to evaluate the quality of compressed data quickly without extensive trial and error. We evaluate our proposed framework on real-world scientific application datasets. Our surrogate-based framework shows superior prediction accuracy, with the RMSE generally lower than 5%. On the other hand, our framework demonstrates robust generalization for prediction across data fields within the same application. Our results show that our approach significantly reduces the error bound selection time and accelerates the downstream evaluation process for decompressed data, making it easier for domain scientists to select optimal error bounds of lossy compression while maintaining data quality that meets their needs. This work bridges the gap between compression ratio optimization and data fidelity, offering a scalable solution for scientific applications that rely on large-scale lossy compression.

K-means is a widely used algorithm in clustering, how-ever, its efficiency is primarily constrained by the computational cost of distance computing. Existing implementations suffer from suboptimal utilization of computational units and lack resilience against soft errors. To address these challenges, we introduce FT K-means, a high-performance GPU-accelerated implementation of K-means with online fault tolerance. We first present a step-wise optimization strategy that achieves competitive performance compared to NVIDIA's cuML library. We further improve FT K-means with a template-based code generation framework that supports different data types and adapts to different input shapes. A novel warp-level tensor-core error correction scheme is proposed to address the failure of existing fault tolerance methods due to mem-ory asynchronization during copy operations. Our experimental evaluations on NVIDIA T4 GPU and A100 GPU demonstrate that FT K-means without fault tolerance outperforms cuML's K-means implementation, showing a performance increase of 10%-300% in scenarios involving irregular data shapes. Moreover, the fault tolerance feature of FT K-means introduces only an overhead of 11%, maintaining robust performance even with tens of errors injected per second.

Lossy compression and asynchronous I/O are two of the most effective solutions for reducing storage overhead and enhancing I/O performance in large-scale high-performance computing (HPC) applications. However, current approaches have limitations that prevent them from fully leveraging lossy compression, and they may also result in task collisions, which restrict the overall performance of HPC applications. To address these issues, we propose an optimization approach for the task scheduling problem that encompasses computation, compression, and I/O. Our algorithm adaptively selects the optimal compression and I/O queue to minimize the performance degradation of the computation. We also introduce an intra-node I/O workload balancing mechanism that evenly distributes the workload across different processes. Additionally, we design a framework that incorporates fine-grained compression, a compressed data buffer, and a shared Huffman tree to fully benefit from our proposed task scheduling. Experimental results with up to 16 nodes and 64 GPUs from ORNL Summit, as well as real-world HPC applications, demonstrate that our solution reduces I/O overhead by up to 3.8× and 2.6× compared to non-compression and asynchronous I/O solutions, respectively.

Lossy compression can be an effective tool in AI training and inference to reduce memory requirements, storage footprint, and in some cases, execution time. With the rise of novel architectures designed to accelerate AI workloads, compression can continue to serve these purposes, but must be adapted to the new accelerators. Due to programmability and architectural differences, existing lossy compressors cannot be directly ported to and are not optimized for any AI accelerator, thus requiring new compression designs.

Today's scientific applications running on supercomputers produce large volumes of data, leading to critical data storage and communication challenges. To tackle the challenges, error-bounded lossy compression is commonly adopted since it can reduce data size drastically within a user-defined error threshold. Previous work has shown that compression techniques can significantly reduce the storage and I/O overhead while retaining good data quality. However, the existing compressors are mainly designed for CPU and GPU. As new AI chips are being incorporated into supercomputers and increasingly used for accelerating scientific computing, there is a growing demand for efficient data compression on the new architecture. In this paper, we propose an efficient lossy compressor, CereSZ, based on the Cerebras CS-2 system. The compression algorithm is mapped onto Cerebras using both data parallelism and pipeline parallelism. In order to achieve a balanced workload on each processing unit, we propose an algorithm to evenly distribute the pipeline stages. Our experiments with six scientific datasets demonstrate that CereSZ can achieve a throughput from 227.93 GB/s to 773.8 GB/s, 2.43x to 10.98x faster than existing GPU compressors.

With the promise of federated learning (FL) to allow for geographically-distributed and highly personalized services, the efficient exchange of model updates between clients and servers becomes crucial. FL, though decentralized, often faces communication bottlenecks, especially in resource-constrained scenarios. Existing data compression techniques like gradient sparsification, quantization, and pruning offer some solutions, but may compromise model performance or necessitate expensive retraining. In this paper, we introduce FedSZ, a specialized lossy-compression algorithm designed to minimize the size of client model updates in FL. FedSZ incorporates a comprehensive compression pipeline featuring data partitioning, lossy and lossless compression of model parameters and metadata, and serialization. We evaluate FedSZ using a suite of error-bounded lossy compressors, ultimately finding SZ2 to be the most effective across various model architectures and datasets including AlexNet, MobileNetV2, ResNet50, CIFAR-10, Caltech101, and Fashion-MNIST. Our study reveals that a relative error bound${10}^{-2}$achieves an optimal tradeoff, compressing model states between 5.55-12.61× while maintaining inference accuracy within < 0.5 % of uncompressed results. Additionally, the runtime overhead of FedSZ is < 4.7% or between of the wall-clock communication-round time, a worthwhile trade-off for reducing network transfer times by an order of magnitude for networks bandwidths < 350Mbps. Intriguingly, we also find that the error introduced by FedSZ could potentially serve as a source of differentially private noise, opening up new avenues for privacy-preserving FL.

Lossy compression has been employed to reduce the unprecedented amount of data produced by today's large-scale scientific simulations and high-resolution instruments. To avoid loss of critical information, state-of-the-art scientific lossy compressors provide error controls on relatively simple metrics such as absolute error bound. However, preserving these metrics does not translate to the preservation of topological features, such as critical points in vector fields. To address this problem, we investigate how to effectively preserve the sign of determinant in error-controlled lossy compression, as it is an important quantity of interest used for the robust detection of many topological features. Our contribution is three-fold. (1) We develop a generic theory to derive the allowable perturbation for one row of a matrix while preserving its sign of the determinant. As a practical use-case, we apply this theory to preserve critical points in vector fields because critical point detection can be reduced to the result of the point-in-simplex test that purely relies on the sign of determinants. (2) We optimize this algorithm with a speculative compression scheme to allow for high compression ratios and efficiently parallelize it in distributed environments. (3) We perform solid experiments with real-world datasets, demonstrating that our method achieves up to 440% improvements in compression ratios over state-of-the-art lossy compressors when all critical points need to be preserved. Using the parallelization strategies, our method delivers up to 1.25 x and 4.38 x performance speedup in data writing and reading compared with the vanilla approach without compression.

Scientific simulations running on HPC facilities generate massive amount of data, putting significant pressure onto supercomputers’ storage capacity and network bandwidth. To alleviate this problem, there has been a rich body of work on reducing data volumes via error-controlled lossy compression. However, fixed-ratio compression is not very well-supported, not allowing users to appropriately allocate memory/storage space or know the data transfer time over the network in advance. To address this problem, recent ratio-controlled frameworks, such as FXRZ, have incorporated methods to predict required error bound settings to reach a user-specified compression ratio. However, these approaches fail to achieve fixed-ratio compression in an accurate, efficient and scalable fashion on diverse datasets and compression algorithms.

GPU-aware collective communication has become a major bottleneck for modern computing platforms as GPU computing power rapidly rises. A traditional approach is to directly integrate lossy compression into GPU-aware collectives, which can lead to serious performance issues such as underutilized GPU devices and uncontrolled data distortion. In order to address these issues, in this paper, we propose gZCCL, a first-ever general framework that designs and optimizes GPU-aware, compression-enabled collectives with an accuracy-aware design to control error propagation. To validate our framework, we evaluate the performance on up to 512 NVIDIA A100 GPUs with real-world applications and datasets. Experimental results demonstrate that our gZCCL-accelerated collectives, including both collective computation (Allreduce) and collective data movement (Scatter), can outperform NCCL as well as Cray MPI by up to 4.5 × and 28.7 ×, respectively. Furthermore, our accuracy evaluation with an image-stacking application confirms the high reconstructed data quality of our accuracy-aware framework.

Due to the increasing scale of high-performance computing (HPC) systems, transient hardware faults have become a major reliability concern. Consequently, Silent Data Corruptions (SDCs) due to these faults have been a common insidious consequence in GPU applications. Developers often measure the application resilience with a set of program test inputs available in the benchmark suite, assuming the resilience would not fluctuate much among different inputs. However, we observe that this assumption often results in an over-optimistic evaluation for GPU applications. As a result, the subsequent SDC protection following the evaluation can hardly meet the expected reliability bar in the production environment, where applications would run with potentially arbitrary input values. To this end, we propose Druto – a compiler-based automated technique that searches for inputs to incrementally approach the upper bound of a GPU application’s SDC probability. We develop Druto based on the property that the resilience profiles of a small group of representative threads in a GPU kernel can approximately rank various inputs in terms of the overall SDC probability. Therefore, Druto strategically steers the search towards new program inputs that efficiently portray the overall SDC probability. Evaluation shows that the SDC probability derived from Druto’s input generation is as much as 74× higher than that from existing techniques. Moreover, existing techniques cannot find our generated inputs even given 5× more search time.

With the ever-increasing computing power of supercomputers and the growing scale of scientific applications, the efficiency of MPI collective communications turns out to be a critical bottleneck in large-scale distributed and parallel processing. The large message size in MPI collectives is particularly concerning because it can significantly degrade the overall parallel performance. To address this issue, prior research simply applies the off-the-shelf fix-rate lossy compressors in the MPI collectives, leading to suboptimal performance, limited generalizability, and unbounded errors. In this paper, we propose a novel solution, called C-Coll, which leverages error-bounded lossy compression to significantly reduce the message size, resulting in a substantial reduction in communication cost. The key contributions are three-fold. (1) We develop two general, optimized lossy-compression-based frameworks for both types of MPI collectives (collective data movement as well as collective computation), based on their particular characteristics. Our framework not only reduces communication cost but also preserves data accuracy. (2) We customize SZx, an ultra-fast error-bounded lossy compressor, to meet the specific needs of collective communication. (3) We integrate C-Coll into multiple collectives, such as MPI Allreduce, MPI Scatter, and MPI Bcast, and perform a comprehensive evaluation based on real-world scientific datasets. Experiments show that our solution outperforms the original MPI collectives as well as multiple baselines and related efforts by 1.8–2.7×.

Benefiting from the cutting-edge supercomputers that support extremely large-scale scientific simulations, climate research has advanced significantly over the past decades. However, new critical challenges have arisen regarding efficiently storing and transferring large-scale climate data among distributed repositories and databases for post hoc analysis. In this paper, we develop CliZ, an efficient online error-controlled lossy compression method with optimized data prediction and encoding methods for climate datasets across various climate models. On the one hand, we explored how to take advantage of particular properties of the climate datasets (such as mask-map information, dimension permutation/fusion, and data periodicity pattern) to improve the data prediction accuracy. On the other hand, CliZ features a novel multi-Huffman encoding method, which can significantly improve the encoding efficiency. Therefore significantly improving compression ratios. We evaluated CliZ versus many other state-of-the-art error-controlled lossy compressors (including SZ3, ZFP, SPERR, and QoZ) based on multiple real-world climate datasets with different models. Experiments show that CliZ outperforms the second-best compressor (SZ3, SPERR, or QoZ1.1) on climate datasets by 20%-200% in compression ratio. CliZ can significantly reduce the data transfer cost between the two remote Globus endpoints by 32%-38%.

Amid the growing prevalence of artificial intelligence (AI) and deep learning (DL) across industries and science disciplines, high-performance computing (HPC) clusters are increasingly used for DL tasks, in addition to their traditional role in numerical simulations. This shared use of HPC systems for both DL tasks and numerical codes is altering the characteristics of their workloads, leaving many previously observed and well-accepted workload characteristics unchecked, potentially outdated and imprecise, for these new mixed workloads. Thus, to understand these changes and their implications for job scheduling, we conduct a cross-system analysis of job characterization and its scheduling across a range of representative clusters, including two classic HPC clusters (Mira, Theta), two classic DL clusters (Philly, Helios), and a hybrid cluster (Blue Waters).Our cross-system analyses focus on three key aspects: 1) job geometries (job size, run time, arrival interval) and their impacts on scheduling results, 2) job failure patterns and their correlations to job geometries, 3) per-user behaviors and their indication on job scheduling. Through these comparisons, we confirm notable disparity and similarity among different systems (summarized as 8 takeaways), which would help design more efficient job schedulers for the future HPC systems. We further introduce two use case studies (job runtime prediction and adaptive relaxed backfilling) that leverage these new observations and show the improved job scheduling results. In summary, we expect our observations, insights, and systematic analysis approach can be useful for the community in building efficient HPC scheduling for the upcoming hybrid workloads.

GPU-aware collective communication has become a major bottleneck for modern computing platforms as GPU computing power rapidly rises. To address this issue, traditional approaches integrate lossy compression directly into GPU-aware collectives, which still suffer from serious issues such as underutilized GPU devices and uncontrolled data distortion. In this paper, we propose GPU-LCC, a general framework that designs and optimizes GPU-aware, compression-enabled collectives with well-controlled error propagation. To validate our framework, we evaluate the performance on up to 64 NVIDIA A100 GPUs with real-world applications and datasets. Experimental results demonstrate that our GPU-LCC-accelerated collective computation (Allreduce), can outperform NCCL as well as Cray MPI by up to 3.4× and 18.7×, respectively. Furthermore, our accuracy evaluation with an image-stacking application confirms the high reconstructed data quality of our accuracy-aware framework.

Error-bounded lossy compression is a critical technique for significantly reducing scientific data volumes. Compared to CPU-based compressors, GPU-based compressors exhibit substantially higher throughputs, fitting better for today’s HPC applications. However, the critical limitations of existing GPU-based compressors are their low compression ratios and qualities, severely restricting their applicability. To overcome these, we introduce a new GPU-based error-bounded scientific lossy compressor named CUSZ-i, with the following contributions: (1) A novel GPU-optimized interpolation-based prediction method significantly improves the compression ratio and decompression data quality. (2) The Huffman encoding module in CUSZ-i is optimized for better efficiency. (3) CUSZ-i is the first to integrate the NVIDIA Bitcomp-lossless as an additional compression-ratio-enhancing module. Evaluations show that CUSZ-i significantly outperforms other latest GPU-based lossy compressors in compression ratio under the same error bound (hence, the desired quality), showcasing a 476% advantage over the second-best. This leads to CUSZ-i’s optimized performance in several real-world use cases.

As network bandwidth struggles to keep up with rapidly growing computing capabilities, the efficiency of collective communication has become a critical challenge for exa-scale distributed and parallel applications. Traditional approaches directly utilize error-bounded lossy compression to accelerate collective computation operations, exposing unsatisfying performance due to the expensive decompression-operation-compression (DOC) workflow. To address this issue, we present a first-ever homomorphic compression-communication co-design, hZCCL, which enables operations to be performed directly on compressed data, saving the cost of time-consuming decompression and recompression. In addition to the co-design framework, we build a light-weight compressor, optimized specifically for multi-core CPU platforms. We also present a homomorphic compressor with a run-time heuristic to dynamically select efficient compression pipelines for reducing the cost of DOC handling. We evaluate $h \mathbf{Z C C L}$ with up to 512 nodes and across five application datasets. The experimental results demonstrate that our homomorphic compressor achieves a CPU throughput of up to $379.08 \mathrm{~GB} / \mathrm{s}$, surpassing the conventional DOC workflow by up to $36.53 \times$. Moreover, our $\boldsymbol{h Z C C L}$-accelerated collectives outperform two state-of-the-art baselines, delivering speedups of up to $2.12 \times$ and $6.77 \times$ compared to original MPI collectives in single-thread and multi-thread modes, respectively, while maintaining data accuracy.

Existing GPU lossy compressors suffer from expensive data movement overheads, inefficient memory access patterns, and high synchronization latency, resulting in limited throughput. This work proposes cuSZP2, a generic single-kernel error-bounded lossy compressor purely on GPUs designed for applications that require high speed, such as large-scale GPU simulation and large language model training. In particular, CUSZP2 proposes a novel lossless encoding method, optimizes memory access patterns, and hides synchronization latency, achieving extreme end-to-end throughput and optimized compression ratio. Experiments on NVIDIA A100 GPU with 9 real-world HPC datasets demonstrate that, even with higher compression ratios and data quality, CUSZP2 can deliver on average 332.42 and $513.04 \mathrm{~GB} / \mathrm{s}$ end-to-end throughput for compression and decompression, respectively, which is around $2 \times$ of existing pure-GPU compressors and $200 \times$ of CPU-GPU hybrid compressors.

With the ongoing reduction in technology sizes and voltage levels, modern microprocessors are increasingly susceptible to soft errors, corrupting datapath units during program execution. While these error types have received considerable attention recently, existing solutions either confine themselves to limited scopes or incur massive overheads in performance and power consumption, hindering practical usage. In this work, we propose CONDA, a novel error detection technique based on code transformation and static program analysis, achieving versatile datapath protection at low cost. At compile time, ConDa analyzes program characteristics and transforms the original program code without complicating its control-flow and memory access patterns. At runtime, ConDa detects datapath errors with low overhead and latency. The evaluation of 38 benchmarks and a parallel HPC simulation reveals that CONDA only incurs 57.79% runtime overhead, which is 41.84% faster than existing state-of-the-art, with the same level of error detection effectiveness and low detection latency.

Error-bounded lossy compression has been identified as a promising solution for significantly reducing scientific data volumes upon users' requirements on data distortion. For the existing scientific error-bounded lossy compressors, some of them (such as SPERR and FAZ) can reach fairly high compression ratios and some others (such as SZx, SZ, and ZFP) feature high compression speeds, but they rarely exhibit both high ratio and high speed meanwhile. In this paper, we propose HPEZ with newly-designed interpolations and quality-metric-driven auto-tuning, which features significantly improved compression quality upon the existing high-performance compressors, meanwhile being exceedingly faster than high-ratio compressors. The key contributions lie as follows: (1) We develop a series of advanced techniques such as interpolation re-ordering, multi-dimensional interpolation, and natural cubic splines to significantly improve compression qualities with interpolation-based data prediction. (2) The auto-tuning module in HPEZ has been carefully designed with novel strategies, including but not limited to block-wise interpolation tuning, dynamic dimension freezing, and Lorenzo tuning. (3) We thoroughly evaluate HPEZ compared with many other compressors on six real-world scientific datasets. Experiments show that HPEZ outperforms other high-performance error-bounded lossy compressors in compression ratio by up to 140% under the same error bound, and by up to 360% under the same PSNR. In parallel data transfer experiments on the distributed database, HPEZ achieves a significant performance gain with up to 40% time cost reduction over the second-best compressor.

To address the challenges raised by the data management of exascale scientific data, error-bounded lossy compression has been proposed and well-researched as a prominent solution. Among the existing works, a recent trend leverages wavelet transforms in the error-bounded lossy compression task to effectively capture long-term data correlations within the inputs. Applying those transforms as data preprocessors and decorrelators, wavelet-based lossy compressors have achieved optimized compression rate-distortion on several datasets. However, certain significant limitations of wavelet-based compressors have also been observed: On one hand, attributed to the high computational cost of wavelet transforms, wavelet-based compressors suffer from relatively low computational efficiencies compared to other state-of-the-art compressors. On the other hand, one certain type of wavelet transform cannot perform well on all variations of scientific data. Consequently, to further fine-tune the wavelet-based scientific data lossy compression, more in-depth and systematic research and analysis needs to be conducted. In this paper, based on the FAZ auto-tuning-based modular compression framework, we have integrated a great number of wavelet transforms into the framework and evaluated them with various real-world scientific datasets and fields. From the analysis of those evaluations and the comparison to existing state-of-the-art wavelet-based and non-wavelet-based error-bounded lossy compressors, we conclude and present several essential takeaways for designing and optimizing the wavelet-based scientific error-bounded lossy compressor.

The fast growth of computational power and scales of modern super-computing systems have raised great challenges for the management of exascale scientific data. To maintain the usability of scientific data, error-bound lossy compression is proposed and developed as an essential technique for the size reduction of scientific data with constrained data distortion. Among the diverse datasets generated by various scientific simulations, certain datasets cannot be effectively compressed by existing error-bounded lossy compressors with traditional techniques. The recent success of Artificial Intelligence has inspired several researchers to integrate neural networks into error-bounded lossy compressors. However, those works still suffer from limited compression ratios and/or extremely low efficiencies. To address those issues and improve the compression on the hard-to-compress datasets, in this paper, we propose SRNNSZ, which is a deep learning-based scientific error-bounded lossy compressor leveraging the hierarchical data grid expansion paradigm implemented by super-resolution neural networks. SRNN-SZ applies the most advanced super-resolution network HAT for its compression, which is free of time-costing per-data training. In experiments compared with various state-of-the-art compressors, SRNN-SZ achieves up to 75% compression ratio improvements under the same error bound and up to 80% compression ratio improvements under the same PSNR than the second-best compressor.

Seismic imaging is an exploration method for estimating the seismic characteristics of the earth's sub-surface for geologists and geophysicists. Reverse time migration (RTM) is a critical method in seismic imaging analysis. It can produce huge volumes of data that need to be stored for later use during its execution. The traditional solution transfers the vast amount of data to peripheral devices and loads them back to memory whenever needed, which may cause a substantial burden to I/O and storage space. As such, an efficient data compressor turns out to be a very critical solution. In order to get the best overall RTM analysis performance, we develop a novel hybrid lossy compression method (called HyZ), which is not only fairly fast in both compression and decompression but also has a good compression ratio with satisfactory reconstructed data quality for post hoc analysis. We evaluate several state-of-the-art error-controlled lossy compression algorithms (including HyZ, BR, SZx, SZ, SZ-Interp, ZFP, etc.) in a supercomputer. Experiments show that HyZ not only significantly improves the overall performance for RTM by 6.29∼6.60× but also obtains fairly good qualities for both RTM single snapshots and the final stacking image.

Error-bounded lossy compression turns more and more important for the data-moving intensive applications to deal with big datasets efficiently in HPC environments, which often requires knowing the compressibility of the datasets before performing the compression. However, the off-the-shelf state-of-the-art lossy compressors are often driven by error bounds, so the compression ratios cannot be forecasted until the completion of the compression operation. In this paper, we propose a lightweight, robust, easy-to-train model that estimates the compressibility of datasets for different lossy compressors accurately. Our approach combines novel predictors that measure various notions of spatial correlation and smoothness exploited by lossy compressors that are implemented efficiently on the GPU in a framework and that uses mixture model regression to improve robustness with conformal prediction to provide bounds on the estimates. We then use these models with a detailed analysis of speedup to understand the tradeoffs between high speed, consistent speed, and accuracy of the methods on real applications. We evaluate our approach in the context of 3 key applications where compression ratio estimation is highly required.

High Performance Computing (HPC) systems generate a large amount of unstructured/alphanumeric log messages that capture the health state of their components. Due to their design complexity, HPC systems often undergo failures that halt applications (e.g., weather prediction, aerodynamics simulation) execution. However, existing failure prediction methods, which typically seek to extract some information theoretic features, fail to scale both in terms of accuracy and prediction speed, limiting their adoption in real-time production systems. In this paper, differently from existing work and inspired by current transformer-based neural networks which have revolutionized the sequential learning in the natural language processing (NLP) tasks, we propose a novel scalable log-based, self-supervised model (i.e., no need for manual labels), called Time Machine11A Time Machine allows us to travel into the future to observe the health state of HPC system and report back. Here, we travel into the log extension to report an upcoming failure., that predicts (i) forthcoming log events (ii) the upcoming failure and its location and (iii) the expected lead time to failure. Time Machine is designed by combining two stacks of transformer-decoders, each employing the self-attention mechanism. The first stack addresses the failure location by predicting the sequence of log events and then identifying if a failure event is part of that sequence. The lead time to predicted failure is addressed by the second stack. We evaluate Time Machine on four real-world HPC log datasets and compare it against three state-of-the-art failure prediction approaches. Results show that Time Machine significantly outperforms the related works on Bleu, Rouge, MCC, and F1-score in predicting forthcoming events, failure location, failure lead-time, with higher prediction speed.

Today's scientific high-performance computing (HPC) applications are often running on large-scale environments, producing extremely large volumes of data that need to be compressed effectively for efficient storage or data transfer. Error-bounded lossy compression is arguably the most efficient way to this end, because it can get very high compression ratios while controlling the data distortion strictly based on user requirements for compression errors. However, error-bounded lossy compressors may have serious artifact issues in situations with relatively large error bound or high compression ratios, which is highly undesirable to users. In this paper, we compre-hensively characterize the artifacts for multiple state-of-the-art error-bounded lossy compressors (including SZ-1.4, SZ-2.1, SZ-3.0, FPZIP, ZFP, MGARD) and provide an in-depth analysis for the root cause of these artifacts. We summarize the artifact issue into three types and also develop an efficient artifact detection algorithm for each type of artifact. We finally evaluate our artifact detection methods using four scientific datasets, which demonstrates that the proposed methods are able to detect artifact issues under linear time complexity.

Error-controlled lossy compression has been effective in reducing data storage/transfer costs while preserving reconstructed data fidelity based on user-defined error bounds. State-of-the-art error-controlled lossy compressors primarily fo-cus on error control rather than compression size, and thus, compression ratios are unknown until the compression operation is fully completed. Many use cases, however, require knowledge of compression ratios a priori, for example, pre-allocating appropri-ate memory for the compressed data at runtime. In this paper, we propose a novel, efficient Surrogate-based Error-controlled Lossy Compression Ratio Estimation Framework (SECRE), which includes three key features/contributions. (1) We carefully design the SECRE framework, which, in principle, can be applied to different error-bounded lossy compressors. (2) We implement a compression ratio estimation method for four state-of-the-art error-controlled lossy compressors-SZx, SZ3, ZFP, and SPERR-by devising a corresponding lightweight compression surrogate for each. (3) We evaluate the performance and accuracy of SECRE using four real-world scientific simulation datasets. Experiments show that SECREcan obtain highly accurate com-pression ratio estimates (e.g., ~ 1 % estimation errors for SZx) with low execution overhead (e.g., ~ 2 % estimation cost for SZx).

Today's large-scale scientific applications running on high-performance computing (HPC) systems generate vast data volumes. Thus, data compression is becoming a critical technique to mitigate the storage burden and data-movement cost. However, existing lossy compressors for scientific data cannot achieve a high compression ratio and throughput simultaneously, hindering their adoption in many applications requiring fast compression, such as in-memory compression. To this end, in this work, we develop a fast and high- ratio error-bounded lossy compressor on GPUs for scientific data (called FZ-GPU). Specifically, we first design a new compression pipeline that consists of fully parallelized quantization, bitshuffle, and our newly designed fast encoding. Then, we propose a series of deep architectural optimizations for each kernel in the pipeline to take full advantage of CUDA architectures. We propose a warp-level optimization to avoid data conflicts for bit-wise operations in bitshuffle, maximize shared memory utilization, and eliminate unnecessary data movements by fusing different compression kernels. Finally, we evaluate FZ-GPU on two NVIDIA GPUs (i.e., A100 and RTX A4000) using six representative scientific datasets from SDRBench. Results on the A100 GPU show that FZ-GPU achieves an average speedup of 4.2× over cuSZ and an average speedup of 37.0× over a multi-threaded CPU implementation of our algorithm under the same error bound. FZ-GPU also achieves an average speedup of 2.3× and an average compression ratio improvement of 2.0× over cuZFP under the same data distortion.

The increasing volume and velocity of science data necessitate the frequent movement of enormous data volumes as part of routine research activities. As a result, limited wide-area bandwidth often leads to bottlenecks in research progress. However, in many cases, consuming applications (e.g., for analysis, visualization, and machine learning) can achieve acceptable performance on reduced-precision data, and thus researchers may wish to compromise on data precision to reduce transfer and storage costs. Error-bounded lossy compression presents a promising approach as it can significantly reduce data volumes while preserving data integrity based on user-specified error bounds. In this paper, we propose a novel data transfer framework called Ocelot that integrates error-bounded lossy compression into the Globus data transfer infrastructure. We note four key contributions: (1) Ocelot is the first integration of lossy compression in Globus to significantly improve scientific data transfer performance over wide area network (WAN). (2) We propose an effective machine-learning based lossy compression quality estimation model that can predict the quality of error-bounded lossy compressors, which is fundamental to ensure that transferred data are acceptable to users. (3) We develop optimized strategies to reduce the compression time overhead, counter the compute-node waiting time, and improve transfer speed for compressed files. (4) We perform evaluations using many real-world scientific applications across different domains and distributed Globus endpoints. Our experiments show that Ocelot can improve dataset transfer performance substantially, and the quality of lossy compression (time, ratio and data distortion) can be predicted accurately for the purpose of quality assurance.

Today’s scientific applications and advanced instruments are producing extremely large volumes of data everyday, so that error-controlled lossy compression has become a critical technique to the scientific data storage and management. Existing lossy scientific data compressors, however, are designed mainly based on error-control driven mechanism, which cannot be efficiently applied in the fixed-ratio use-case, where a desired compression ratio needs to be reached because of the restricted data processing/management resources such as limited memory/storage capacity and network bandwidth. To address this gap, we propose a low-cost compressor-agnostic feature-driven fixed-ratio lossy compression framework (FXRZ). The key contributions are three-fold. (1) We perform an in-depth analysis of the correlation between diverse data features and compression ratios based on a wide range of application datasets, which is a fundamental work for our framework. (2) We propose a series of optimization strategies that can enable the framework to reach a fairly high accuracy in identifying the expected error configuration with very low computational cost. (3) We comprehensively evaluate our framework using 4 state-of-the-art error-controlled lossy compressors on 10 different snapshots and simulation configuration-based real-world scientific datasets from 4 different applications across different domains. Our experiment shows that FXRZ outperforms the state-of-the-art related work by 108×. The experiments with 4,096 cores on a supercomputer show a performance gain of 1.18∼8.71× than the related work in overall parallel data dumping.

Error-bounded lossy compression has been effective to resolve the big scientific data issue because it has a great potential to significantly reduce the data volume while allowing users to control data distortion based on specified error bounds. However, none of the existing error-bounded lossy compressors can always obtain the best compression quality because of the diverse characteristics of different datasets. In this paper, we develop FAZ, a flexible and adaptive error-bounded lossy compression framework, which projects a fairly high capability of adapting to diverse datasets. FAZ can always keep the compression quality at the best level compared with other state-of-the-art compressors for different datasets. We perform a comprehensive evaluation using 6 real-world scientific applications and 6 other state-of-the-art error-bounded lossy compressors. Experiments show that compared with the other existing lossy compressors, FAZ can improve the compression ratio by up to 120%, 190%, and 75% when setting the same error bound, the same PSNR and the same SSIM, respectively.

Lossy compression is often deployed in scientific applications to reduce data footprint and improve data transfers and I/O performance. Especially for applications requiring on-the-flight compression, it is essential to minimize compression's runtime. In this paper, we design a scheme to improve the performance of cuSZ, a GPU-based lossy compressor. We observe that Huffman coding - used by cuSZ to compress metadata generated during compression - incurs a performance overhead that can be significant, especially for smaller datasets. Our work seeks to reduce the Huffman coding runtime with minimal-to-no impact on cuSZ's compression efficiency.

Today's graphics processing unit (GPU) applications produce vast volumes of data, which are challenging to store and transfer efficiently. Thus, data compression is becoming a critical technique to mitigate the storage burden and communication cost. LZSS is the core algorithm in many widely used compressors, such as Deflate. However, existing GPU-based LZSS compressors suffer from low throughput due to the sequential nature of the LZSS algorithm. Moreover, many GPU applications produce multi-byte data (e.g., int16/int32 index, floating-point numbers), while the current LZSS compression only takes single-byte data as input. To this end, in this work, we propose gpuLZ, a highly efficient LZSS compression on modern GPUs for multi-byte data. The contribution of our work is fourfold: First, we perform an in-depth analysis of existing LZ compressors for GPUs and investigate their main issues. Then, we propose two main algorithm-level optimizations. Specifically, we (1) change prefix sum from one pass to two passes and fuse multiple kernels to reduce data movement between shared memory and global memory, and (2) optimize existing pattern-matching approach for multi-byte symbols to reduce computation complexity and explore longer repeated patterns. Third, we perform architectural performance optimizations, such as maximizing shared memory utilization by adapting data partitions to different GPU architectures. Finally, we evaluate gpuLZ on six datasets of various types with NVIDIA A100 and A4000 GPUs. Results show that gpuLZ achieves up to 272.1× speedup on A4000 and up to 1.4× higher compression ratio compared to state-of-the-art solutions.

Quantum circuit simulations enable researchers to develop quantum algorithms without the need for a physical quantum computer. Quantum computing simulators, however, all suffer from significant memory footprint requirements, which prevents large circuits from being simulated on classical super-computers. In this paper, we explore different lossy compression strategies to substantially shrink quantum circuit tensors in the QTensor package (a state-of-the-art tensor network quantum circuit simulator) while ensuring the reconstructed data satisfy the user-needed fidelity.Our contribution is fourfold. (1) We propose a series of optimized pre- and post-processing steps to boost the compression ratio of tensors with a very limited performance overhead. (2) We characterize the impact of lossy decompressed data on quantum circuit simulation results, and leverage the analysis to ensure the fidelity of reconstructed data. (3) We propose a configurable compression framework for GPU based on cuSZ and cuSZx, two state-of-the-art GPU-accelerated lossy compressors, to address different use-cases: either prioritizing compression ratios or prioritizing compression speed. (4) We perform a comprehensive evaluation by running 9 state-of-the-art compressors on an NVIDIA A100 GPU based on QTensor-generated tensors of varying sizes. When prioritizing compression ratio, our results show that our strategies can increase the compression ratio nearly 10 times compared to using only cuSZ. When prioritizing throughput, we can perform compression at the comparable speed as cuSZx while achieving 3-4× higher compression ratios. Decompressed tensors can be used in QTensor circuit simulation to yield a final energy result within 1-5% of the true energy value.

Modern scientific applications and supercomputing systems are generating large amounts of data in various fields, leading to critical challenges in data storage footprints and communication times. To address this issue, error-bounded GPU lossy compression has been widely adopted, since it can reduce the volume of data within a customized threshold on data distortion. In this work, we propose an ultra-fast error-bounded GPU lossy compressor cuSZp. Specifically, cuSZp computes the linear recurrences with hierarchical parallelism to fuse the massive computation into one kernel, drastically improving the end-to-end throughput. In addition, cuSZp adopts a block-wise design along with a lightweight fixed-length encoding and bit-shuffle inside each block such that it achieves high compression ratios and data quality. Our experiments on NVIDIA A100 GPU with 6 representative scientific datasets demonstrate that cuSZp can achieve an ultra-fast end-to-end throughput (95.53x compared with cuSZ) along with a high compression ratio and high reconstructed data quality.

As supercomputers advance towards exascale capabilities, computational intensity increases significantly, and the volume of data requiring storage and transmission experiences exponential growth. Adaptive Mesh Refinement (AMR) has emerged as an effective solution to address these two challenges. Concurrently, error-bounded lossy compression is recognized as one of the most efficient approaches to tackle the latter issue. Despite their respective advantages, few attempts have been made to investigate how AMR and error-bounded lossy compression can function together. To this end, this study presents a novel in-situ lossy compression framework that employs the HDF5 filter to improve both I/O costs and boost compression quality for AMR applications. We implement our solution into the AMReX framework and evaluate on two real-world AMR applications, Nyx and WarpX, on the Summit supercomputer. Experiments with 4096 CPU cores demonstrate that AMRIC improves the compression ratio by up to 81× and the I/O performance by up to 39× over AMReX's original compression solution.

Today's scientific simulations require a significant reduction of data volume because of extremely large amounts of data they produce and the limited I/O bandwidth and storage space. Error-bounded lossy compression has been considered one of the most effective solutions to the above problem. In practice, however, the best-fit compression method often needs to be customized or optimized in particular because of diverse characteristics in different datasets and various user requirements on the compression quality and performance. In this paper, we address this issue with a novel modular, composable compression framework named SZ3. Our contributions are four-folds. (1) We develop SZ3 which features an innovative modular abstraction for the prediction-based compression framework, such that compression modules can be plugged in easily to create new compressors based on characteristics of data and user requirements. (2) We create a new compression pipeline by SZ3 for GAMESS data, which significantly improves the compression ratios over state-of-the-art compressors. (3) We develop an adaptive compression pipeline by SZ3 for APS data with minimal efforts, which leads to the best rate-distortion among all existing error-bounded lossy compressors for any bit-rate. (4) We compare the sustainability of SZ3 with leading error-bounded prediction-based compressors, and then demonstrate the necessity of diverse pipelines by integrating and evaluating several compression pipelines on diverse scientific datasets from multiple disciplines. Experiments show that SZ3 incurs very limited overhead in compressor integration and our customized compression pipelines lead to up to 20% improvement in compression ratios under the same data distortion, when compared with the best existing approach.

The objective of this work is to develop error-bounded lossy compression methods to preserve topological features in 2D and 3D vector fields. Specifically, we explore the preservation of critical points in piecewise linear and bilinear vector fields. We define the preservation of critical points as, without any false positive, false negative, or false type in the decompressed data, (1) keeping each critical point in its original cell and (2) retaining the type of each critical point (e.g., saddle and attracting node). The key to our method is to adapt a vertex-wise error bound for each grid point and to compress input data together with the error bound field using a modified lossy compressor. Our compression algorithm can be also embarrassingly parallelized for large data handling and in situ processing. We benchmark our method by comparing it with existing lossy compressors in terms of false positive/negative/type rates, compression ratio, and various vector field visualizations with several scientific applications.

The enormous volume of data generated by large-scale instruments and simulations poses significant challenges in archiving, transferring, sharing and analyzing data for various scientific groups. Lossy reduction techniques are vital to reducing data size to acceptable levels. However, putting more information content per bit, increases the severity of loss if perturbed by malicious users or hardware failures. In the worst case, the entire dataset is compromised. Malevolent alteration or destruction of datasets containing crucial discoveries can completely invalidate research outcomes in scientific studies. Therefore, it is critical to integrate compression and encryption to handle data securely and efficiently. The current state-of-the-art combination technique Cmpr- Encr handles compression and encryption as two distinct processes. This reduces the compression ratio and bandwidth, especially for hard-to-compress datasets. In this paper, we propose two data protection strategies that work in conjunction with the lossy compressor SZ: Encr-Quant and Encr-Huffman, and carefully evaluate the overhead they introduce on compression bandwidth and ratio. Based on the results of testing with real-world scientific datasets, we find that the cost of Encr-Quant varies with the dataset's properties and requires cautious selection. Encr-Huffman is able to maintain more than 99% of the original compression ratio while saving 6.5% in compression time compared to SZ. Applying Cmpr-Encr leads to a reduction in compression bandwidth, whereas Encr-Huffman increases bandwidth by 3.1% over the SZ, on average.

Today's scientific high-performance computing applications and advanced instruments are producing vast volumes of data across a wide range of domains, which impose a serious burden on data transfer and storage. Error-bounded lossy compression has been developed and widely used in the scientific community because it not only can significantly reduce the data volumes but also can strictly control the data distortion based on the user-specified error bound. Existing lossy compressors, however, cannot offer ultrafast compression speed, which is highly demanded by numerous applications or use cases (such as in-memory compression and online instrument data compression). In this paper, we propose a novel ultrafast error-bounded lossy compressor that can obtain fairly high compression performance on both CPUs and GPUs and with reasonably high compression ratios. The key contributions are threefold. (1) We propose a generic error-bounded lossy compression framework---called SZx---that achieves ultrafast performance through its novel design comprising only lightweight operations such as bitwise and addition/subtraction operations, while still keeping a high compression ratio. (2) We implement SZx on both CPUs and GPUs and optimize the performance according to their architectures. (3) We perform a comprehensive evaluation with six real-world production-level scientific datasets on both CPUs and GPUs. Experiments show that SZx is 2~16x faster than the second-fastest existing error-bounded lossy compressor (either SZ or ZFP) on CPUs and GPUs, with respect to both compression and decompression.

Error-bounded lossy compression is one of the most effective techniques for reducing scientific data sizes. However, the traditional trial-and-error approach used to configure lossy compressors for finding the optimal trade-off between reconstructed data quality and compression ratio is prohibitively expensive. To resolve this issue, we develop a general-purpose analytical ratio-quality model based on the prediction-based lossy compression framework, which can effectively foresee the reduced data quality and compression ratio, as well as the impact of lossy compressed data on post-hoc analysis quality. Our analytical model significantly improves the prediction-based lossy compression in three use-cases: (1) optimization of predictor by selecting the best-fit predictor; (2) memory compression with a target ratio; and (3) in-situ compression optimization by fine-grained tuning error-bounds for various data partitions. We evaluate our analytical model on 10 scientific datasets, demonstrating its high accuracy (93.47% accuracy on average) and low computational cost (up to 18.7x lower than the trial-and-error approach) for estimating the compression ratio and the impact of lossy compression on post-hoc analysis quality. We also verify the high efficiency of our ratio-quality model using different applications across the three use-cases. In addition, our experiment demonstrates that our modeling-based approach reduces the time to store the 3D RTM data with HDF5 by up to 3.4 x with 128 CPU cores over the traditional solution.

Molecular dynamics (MD) has been widely used in today's scientific research across multiple domains including materials science, biochemistry, biophysics, and structural biology. MD simulations can produce extremely large amounts of data in that each simulation could involve a large number of atoms (up to trillions) for a large number of timesteps (up to hundreds of millions). In this paper, we perform an in-depth analysis of a number of MD simulation datasets and then develop an efficient error-bounded lossy compressor that can significantly improve the compression ratios. The contributions are fourfold. (1) We characterize a number of MD datasets and summarize two commonly-used execution models. (2) We develop an adaptive error-bounded lossy compression framework (called MDZ), which can optimize the compression for both execution models adaptively by taking advantage of their specific characteristics. (3) We compare our solution with six other state-of-the-art related works by using three MD simulation packages each with multiple configurations. Experiments show that our solution has up to 233 % higher compression ratios than the second-best lossy compressor in most cases. (4) We demonstrate that MDZ is fully capable of handing particle data beyond MD simulations.

System failures are expected to be frequent in the exascale era such as current Petascale systems. The health of such systems is usually determined from challenging analysis of large amounts of unstructured & redundant log data. In this paper, we leverage log data and propose Clairvoyant, a novel self-supervised (i.e., no labels needed) model to predict node failures in HPC systems based on a recent deep learning approach called transformer-decoder and the self-attention mechanism. Clairvoyant predicts node failures by (i) predicting a sequence of log events and then (ii) identifying if a failure is a part of that sequence. We carefully evaluate Clairvoyant and another state-of-the-art failure prediction approach - Desh, based on two real-world system log datasets. Experiments show that Clairvoyant is significantly better: e.g., it can predict node failures with an average Bleu, Rouge, and MCC scores of 0.90, 0.78, and 0.65 respectively while Desh scores only 0.58, 0.58, and 0.25. More importantly, this improvement is achieved with faster training and prediction time, with Clairvoyant being about 25X and 15X faster than Desh respectively.

More and more HPC applications require fast and effective compression techniques to handle large volumes of data in storage and transmission. Not only do these applications need to compress the data effectively during simulation, but they also need to perform decompression efficiently for post hoc analysis. SZ is an error-bounded lossy compressor for scientific data, and cuSZ is a version of SZ designed to take advantage of the GPU's power. At present, cuSZ's compression performance has been optimized significantly while its decompression still suffers considerably lower performance because of its sophisticated loss-less compression step-a customized Huffman decoding. In this work, we aim to significantly improve the Huffman decoding performance for cuSZ, thus improving the overall decompression performance in turn. To this end, we first investigate two state-of-the-art GPU Huffman decoders in depth. Then, we propose a deep architectural optimization for both algorithms. Specifically, we take full advantage of CUDA GPU architectures by using shared memory on decoding/writing phases, online tuning the amount of shared memory to use, improving memory access patterns, and reducing warp divergence. Finally, we evaluate our optimized decoders on an Nvidia V100 GPU using eight representative scientific datasets. Our new decoding solution obtains an average speedup of 3.64× over cuSZ's Huffman decoder and improves its overall decompression performance by 2.43× on average.

Modern HPC applications produce increasingly large amounts of data, which limits the performance of current extreme-scale systems. Lossy compression, helps to mitigate this issue by decreasing the size of data generated by these applications. SZ, a current state-of-the-art lossy compressor, is able to achieve high compression ratios, but its prediction/quantization methods contain RAW dependencies that prevent parallelizing this step of the compression. Recent work proposes a parallel dual prediction/quantization algorithm for GPUs which removes these dependencies. However, some HPC systems and applications do not use GPUs, and could still benefit from the fine-grained parallelism of this method. Using the dual-quantization technique, we implement and optimize a SIMD vectorized CPU version of SZ (vecSZ), and create a heuristic for selecting the optimal block size and vector length. We propose a novel block padding algorithm to decrease the number of unpredictable values along compression block borders and find it reduces the number of prediction outliers by up to 100%. We measure performance of our vecSZ against an CPU version of SZ using dual-quantization, pSZ, as well as SZ-1.4. Using real-world scientific datasets, we evaluate vecSZ on the Intel Skylake and AMD Rome architectures. vecSZ results in up to 32% improvement in rate-distortion and up to 15× speedup over SZ-1.4, achieving a prediction and quantization bandwidth in excess of 3.4 GB/s.

With the ever-shrinking size of transistors and increasing scale of applications, silent data corruptions (SDCs) have become a common yet serious issue in HPC applications. Selective instruction duplication (SID) is a popular fault-tolerance technique that can obtain a high SDC coverage with low-performance overhead, as it selects the most vulnerable parts of a program for protection with priority. However, existing studies of SID are confined to single program input in the evaluation, assuming that the error resilience of the program remains similar across inputs, leading to a drastic loss of SDC coverage from SID when the protected program runs different inputs. Hence, we proposed Sentinel, an automated compiler-based framework to mitigate the loss of SDC coverage. Evaluation results show that Sentinel can effectively mitigate the loss of SDC coverage (up to 97.00%) across multiple inputs, which significantly hardens existing SID techniques.

With the ever-shrinking size of transistors, silent data corruptions (SDCs) are becoming a common yet serious issue in HPC. Selective instruction duplication (SID) is a widely used fault-tolerance technique that can obtain high SDC coverage with low performance overhead. However, existing SID methods are confined to single program input in its assessment, assuming that error resilience of a program remains similar across inputs. Nevertheless, we observe that the assumption cannot always hold, leading to a drastic loss in SDC coverage across different inputs, compromising HPC reliability. We notice that the SDC coverage loss correlates with a small set of instructions - we call them incubative instructions, which reveal elusive error propagation characteristics across multiple inputs. We propose Minpsid, an automated SID framework that automatically identifies and re-prioritizes incubative instructions in a given program to enhance SDC coverage. Evaluation shows Minpsid can effectively mitigate the loss of SDC coverage across multiple inputs.

Lossy compression is one of the most efficient solutions to reduce storage overhead and improve I/O performance for HPC applications. However, existing parallel I/O libraries cannot fully utilize lossy compression to accelerate parallel write due to the lack of deep understanding on compression-write performance. To this end, we propose to deeply integrate predictive lossy compression with HDF5 to significantly improve the parallel-write performance. Specifically, we propose analytical models to predict the time of compression and parallel write before the actual compression to enable compression-write overlapping. We also introduce an extra space in the process to handle possible data overflows resulting from prediction uncertainty in compression ratios. Moreover, we propose an optimization to reorder the compression tasks to increase the overlapping efficiency. Experiments with up to 4,096 cores from Summit show that our solution improves the write performance by up to$4.5\times$and$2.9\times$over the non-compression and lossy compression solutions, respectively, with only 1.5% storage overhead (compared to original data) on two real-world HPC applications.

With ever-increasing execution scale of the high performance computing (HPC) applications, vast amount of data are being produced by scientific research every day. Error-bounded lossy compression has been considered a very promising solution to address the big-data issue for scientific applications, because it can significantly reduce the data volume with low time cost meanwhile allowing users to control the compression errors with a specified error bound. The existing error-bounded lossy compressors, however, are all developed based on inflexible designs or compression pipelines, which cannot adapt to diverse compression quality requirements/metrics favored by different application users. In this paper, we propose a novel dynamic quality metric oriented error-bounded lossy compression frame-work, namely QoZ. The detailed contribution is three fold. (1) We design a novel highly-parameterized multi-level interpolation-based data predictor, which can significantly improve the overall compression quality with the same compressed size. (2) We design the error bounded lossy compression framework QoZ based on the adaptive predictor, which can auto-tune the critical parameters and optimize the compression result according to user-specified quality metrics during online compression. (3) We evaluate QoZ carefully by comparing its compression quality with multiple state-of-the-arts on various real-world scientific application datasets. Experiments show that, compared with the second best lossy compressor, QoZ can achieve up to 70% compression ratio improvement under the same error bound, up to 150% compression ratio improvement under the same PSNR, or up to 270% compression ratio improvement under the same SSIM.

Today's scientific simulations and instruments are producing a large amount of data, leading to difficulties in storing, transmitting, and analyzing these data. While error-controlled lossy compressors are effective in significantly reducing data volumes and efficiently developing databases for multiple scientific applications, they mainly support error controls on raw data, which leaves a significant gap between the data and user's downstream analysis. This may cause unqualified uncertainties in the outcomes of the analysis, a.k.a quantities of interest (QoIs), which are the major concerns of users in adopting lossy compression in practice. In this paper, we propose rigorous mathematical theories to preserve four families of QoIs that are widely used in scientific analysis during lossy compression along with practical implementations. Specifically, we first develop the error control theory for univariate QoIs which are essential for computing physical properties such as kinetic energy, followed by multivariate QoIs that are more commonly used in real-world applications. The proposed method is integrated into a state-of-the-art compression framework in a modular fashion, which could easily adapt to new QoIs and new compression algorithms. Experiments on real-world datasets demonstrate that the proposed method provides faithful error control on important QoIs including kinetic energy, regional average, and isosurface without trials and errors, while offering compression ratios that are up to 4X of the compression ratios provided by state-of-the-art compressors.

Vast volumes of data are produced by today's scientific simulations and advanced instruments. These data cannot be stored and transferred efficiently because of limited I/O bandwidth, network speed, and storage capacity. Error-bounded lossy compression can be an effective method for addressing these issues: not only can it significantly reduce data size, but it can also control the data distortion based on user-defined error bounds. In practice, many scientific applications have specific requirements or constraints for lossy compression, in order to guarantee that the reconstructed data are valid for post hoc analysis. For example, some datasets contain irrelevant data that should be isolated in particular and users often have intuition regarding value ranges, geospatial regions, and other data subsets that are crucial for subsequent analysis. Existing state-of-the-art error-bounded lossy compressors, however, do not consider these constraints during compression, resulting in inferior compression ratios with respect to user's post hoc analysis, due to the fact that the data itself provides little or no value for post hoc analysis. In this work we address this issue by proposing an optimized framework that can preserve diverse constraints during the error-bounded lossy compression, e.g., cleaning the irrelevant data, efficiently preserving different precision for multiple value intervals, and allowing users to set diverse precision over both regular and irregular regions. We perform our evaluation on a supercomputer with up to 2,100 cores. Experiments with six real-world applications show that our proposed diverse constraints based error-bounded lossy compressor can obtain a higher visual quality or data fidelity on reconstructed data with the same or even higher compression ratios compared with the traditional state-of-the-art compressor SZ. Our experiments also demonstrate very good scalability in compression performance compared with the I/O throughput of the parallel file system.

Lossless compressors have very low compression ratios that do not meet the needs of today’s large-scale scientific applications that produce vast volumes of data. Error-bounded lossy compression (EBLC) is considered a critical technique for the success of scientific research. Although EBLC allows users to set an error bound for the compression, users have been unable to specify the requirements on the compression quality, limiting practical use. Our contributions are: (1) We formulate the problem of configuring EBLC to preserve a user-defined metric as an optimization problem. This allows many classes of new metrics to be preserved, which improves over current practices. (2) We present a framework, OptZConfig, that can adapt to improvements in the search algorithm, compressor, and metrics with minimal changes, enabling future advancements in this area. (3) We demonstrate the advantages of our approach against the leading methods to configure compressors to preserve specific metrics. Our approach improves compression ratios against a specialized compressor by up to$3\times$, has a 56× speedup over FRaZ, 1000× speedup over MGARD-QOI post tuning, and 110× speedup over systematic approaches which had not been bounded by compressors before.

In the past decades, various lossy compressors have been studied broadly due to the ever-increasing volume of data being produced by today’s scientific applications. SZ has been one of the best error-bounded lossy compressors ever raised, and it has a flexible framework that includes four adjustable steps: prediction, quantization, variable-length encoding, and lossless compression. In this paper, we improve the lossy compression performances of the SZ compression model by exploring different existing lossless compression techniques using the Squash data compression benchmark. Specifically, we first characterize the bytes outputted by the first three steps in SZ, then we investigate the best lossless compressor with different datasets and different error bounds. We perform our exploration by testing 8 widely used lossless compressors under different configurations together with SZ over five well-known scientific simulation datasets. Our experiments show that adopting the best-fit lossless compressor selected based on our analysis can improve the overall compression speed by up to 40% compared to the previous lossless compression technique used in SZ with the comparable quality of reconstructed data.

Error-bounded lossy compression is becoming an indispensable technique for the success of today’s scientific projects with vast volumes of data produced during the simulations or instrument data acquisitions. Not only can it significantly reduce data size, but it also can control the compression errors based on user-specified error bounds. Autoencoder (AE) models have been widely used in image compression, but few AE-based compression approaches support error-bounding features, which are highly required by scientific applications. To address this issue, we explore using convolutional autoencoders to improve error-bounded lossy compression for scientific data, with the following three key contributions. (1) We provide an in-depth investigation of the characteristics of various autoencoder models and develop an error-bounded autoencoder-based framework in terms of the SZ model. (2) We optimize the compression quality for main stages in our designed AE-based error-bounded compression framework, fine-tuning the block sizes and latent sizes and also optimizing the compression efficiency of latent vectors. (3) We evaluate our proposed solution using five real-world scientific datasets and comparing them with six other related works. Experiments show that our solution exhibits a very competitive compression quality from among all the compressors in our tests. In absolute terms, it can obtain a much better compression quality (100% $\sim$ 800% improvement in compression ratio with the same data distortion) compared with SZ2.1 and ZFP in cases with a high compression ratio.

Deep learning applications are rapidly gaining traction both in industry and scientific computing. Unsurprisingly, there has been significant interest in adopting deep learning at a very large scale on supercomputing infrastructures for a variety of scientific applications. A key issue in this context is how to find an appropriate model architecture that is suitable to solve the problem. We call this the neural architecture search (NAS) problem. Over time, many automated approaches have been proposed that can explore a large number of candidate models. However, this remains a time-consuming and resource expensive process: the candidates are often trained from scratch for a small number of epochs in order to obtain a set of top-K best performers, which are fully trained in a second phase. To address this problem, we propose a novel method that leverages checkpoints of previously discovered candidates to accelerate NAS. Based on the observation that the candidates feature high structural similarity, we propose the idea that new candidates need not be trained starting from random weights, but rather from the weights of similar layers of previously evaluated candidates. Thanks to this approach, the convergence of the candidate models can be significantly accelerated and produces candidates that are statistically better based on the objective metrics. Furthermore, once the top-K models are identified, our approach provides a significant speed-up (1.4 ~ 1.5 × on the average) for the full training.

Error-bounded lossy compression is a critical technique for significantly reducing scientific data volumes. With ever-emerging heterogeneous high-performance computing (HPC) architecture, GPU-accelerated error-bounded compressors (such as CUSZ and cuZFP) have been developed. However, they suffer from either low performance or low compression ratios. To this end, we propose CUSZ+ to target both high compression ratios and throughputs. We identify that data sparsity and data smoothness are key factors for high compression throughputs. Our key contributions in this work are fourfold: (1) We propose an efficient compression workflow to adaptively perform run-length encoding and/or variable-length encoding. (2) We derive Lorenzo reconstruction in decompression as multidimensional partial-sum computation and propose a fine-grained Lorenzo reconstruction algorithm for GPU architectures. (3) We carefully optimize each of CUSZ kernels by leveraging state-of-the-art CUDA parallel primitives. (4) We evaluate CU SZ+ using seven real-world HPC application datasets on V100 and A100 GPUs. Experiments show CUSZ+ improves the compression throughputs and ratios by up to 18.4× and 5.3×, respectively, over CUSZ on the tested datasets.

Lossy compression is becoming an indispensable technique for the success of today’s extreme-scale high-performance computing projects that produce vast volumes of data during scientific simulations or instrument data acquisitions. Comprehensively understanding the compression quality and performance of different lossy compressors is critical to selecting the best-fit compressors and using them properly and efficiently in practice. A few lossy compression assessment tools (e.g., Z-checker) have been developed, but none of them support the execution in a GPU environment. This is a significant gap because many recent extreme-scale applications and lossy compressors (e.g., cuSZ) can run entirely within GPUs. In this work, we develop an efficient lossy compression measuring system (called cuZ-Checker) on the GPU platform, which aims to perform the lossy compression quality and performance assessment completely within the GPU environment. Our contribution is threefold. (1) We develop a novel GPU-based lossy compression measuring framework using a computation pattern-based design approach. This approach classifies the computing-intensive metrics into three categories based on their patterns which creates large opportunities for kernel fusion and data reuse. (2) For each pattern in cuZ-Checker, we develop a CUDA kernel and provide fine-grained optimizations to boost its performance. (3) We thoroughly evaluate our cuZ-checker on a V100 GPU using four real-world scientific application datasets. Experiments show that cuZ-Checker can significantly accelerate the overall lossy compression assessment performance by $23X \sim31X$ compared with the OpenMP-based multithreading CPU performance. To the best of our knowledge, this is the first lossy compression measuring system designed for GPU devices.

Today's large-scale systems such as High Performance Computing (HPC) Systems are designed/utilized towards exascale computing, inevitably decreasing its reliability due to the increasing design complexity. HPC systems conduct extensive logging of their execution behaviour. In this paper, we leverage the inherent meaning behind the log messages and propose a novel sentiment analysis-based approach for the error detection in large-scale systems, by automatically mining the sentiments in the log messages. Our contributions are four-fold. (1) We develop a machine learning (ML) based approach to automatically build a sentiment lexicon, based on the system log message templates. (2) Using the sentiment lexicon, we develop an algorithm to detect system errors. (3) We develop an algorithm to identify the nodes and components with erroneous behaviors, based on sentiment polarity scores. (4) We evaluate our solution vs. other state-of-the-art machine/deep learning algorithms based on three representative supercomputers' system logs. Experiments show that our error detection algorithm can identify error messages with an average MCC score and f-score of 91% and 96% respectively, while state of the art ML/deep learning model (LSTM) obtains only 67% and 84%. To the best of our knowledge, this is the first work leveraging the sentiments embedded in log entries of large-scale systems for system health analysis.

Vast volumes of scientific data cannot be stored and transferred efficiently because of limited I/O bandwidth, network bandwidth, and storage capacity. Error-bounded lossy compression can be an effective method for resolving these big data issues, since not only can it significantly reduce the data size but it can also control the data distortion based on user-defined error bounds. In practice, many scientific applications have specific data fidelity requirements across different value ranges/intervals of the dataset for the lossy compression, in order to guarantee that the reconstructed data are valid for post hoc analysis. Existing state-of-the-art error-bounded lossy compressors, however, do not support multi-range based error-bounds in the lossy compression, leaving a critical gap that hampers their effective use in practice. In this work, we address this issue by proposing a multi-range based error-bounded lossy compressor based on the state-of-the-art SZ lossy compressor. Our approach allows users to set different error bounds in different value ranges for a compressoin task. We evaluate our approach on several real-world datasets and show that it can obtain a higher visual quality or data fidelity on reconstructed data with the same or even higher compression ratios achieved by SZ.

Today's scientific simulations are producing vast volumes of data that cannot be stored and transferred efficiently because of limited storage capacity, parallel I/O bandwidth, and network bandwidth. The situation is getting worse over time because of the ever-increasing gap between relatively slow data transfer speed and fast-growing computation power in modern supercomputers. Error-bounded lossy compression is becoming one of the most critical techniques for resolving the big scientific data issue, in that it can significantly reduce the scientific data volume while guaranteeing that the reconstructed data is valid for users because of its compression-error-bounding feature. In this paper, we present a novel error-bounded lossy compressor based on a state-of-the-art prediction-based compression framework. Our solution exhibits substantially better compression quality than all of the existing error-bounded lossy compressors, with comparable compression speed. Specifically, our contribution is threefold. (1) We provide an in-depth analysis of why the best-existing prediction-based lossy compressor can only minimally improve the compression quality. (2) We propose a dynamic spline interpolation approach with a series of optimization strategies that can significantly improve the data prediction accuracy, substantially improving the compression quality in turn. (3) We perform a thorough evaluation using six real-world scientific simulation datasets across different science domains to evaluate our solution vs. all other related works. Experiments show that the compression ratio of our solution is higher than that of the second-best lossy compressor by 20% 460% with the same error bound in most of the cases.

Today's high-performance computing (HPC) applications are producing vast volumes of data, which are challenging to store and transfer efficiently during the execution, such that data compression is becoming a critical technique to mitigate the storage burden and data movement cost. Huffman coding is arguably the most efficient Entropy coding algorithm in information theory, such that it could be found as a fundamental step in many modern compression algorithms such as DEFLATE. On the other hand, today's HPC applications are more and more relying on the accelerators such as GPU on supercomputers, while Huffman encoding suffers from low throughput on GPUs, resulting in a significant bottleneck in the entire data processing. In this paper, we propose and implement an efficient Huffman encoding approach based on modern GPU architectures, which addresses two key challenges: (1) how to parallelize the entire Huffman encoding algorithm, including codebook construction, and (2) how to fully utilize the high memory-bandwidth feature of modern GPU architectures. The detailed contribution is fourfold. (1) We develop an efficient parallel codebook construction on GPUs that scales effectively with the number of input symbols. (2) We propose a novel reduction based encoding scheme that can efficiently merge the codewords on GPUs. (3) We optimize the overall GPU performance by leveraging the state-of-the-art CUDA APIs such as Cooperative Groups. (4) We evaluate our Huffman encoder thoroughly using six real-world application datasets on two advanced GPUs and compare with our implemented multithreaded Huffman encoder. Experiments show that our solution can improve the encoding throughput by up to 5.0× and 6.8× on NVIDIA RTX 5000 and V100, respectively, over the state-of-the-art GPU Huffman encoder, and by up to 3.3× over the multithread encoder on two 28-core Xeon Platinum 8280 CPUs.

Today's exa-scale scientific applications or advanced instruments are producing vast volumes of data, which need to be shared/transferred through the network/devices with relatively low bandwidth (e.g., data sharing on WAN or transferring from edge devices to supercomputers). Lossy compression is one of the candidate strategies to address the big data issue. However, little work was done to make it resilient against silent errors, which may happen during the stage of compression or data transferring. In this paper, we propose a resilient error-bounded lossy compressor based on the SZ compression framework. Specifically, we design a new independent-block-wise model that decomposes the entire dataset into many independent sub-blocks to compress. Then, we design and implement a series of error detection/correction strategies elaboratively for each stage of SZ. Our method is arguably the first algorithm-based fault tolerance (ABFT) solution for lossy compression. Our proposed solution incurs negligible execution overhead in the fault-free situation. Upon soft errors happening, it ensures decompressed data strictly bounded within user's requirement with a very limited degradation of compression ratio and low overhead.

Cloud platforms can provide flexible and cost-effective environments for parallel applications. However, the resource over-commitment issues, i.e., cloud providers often provide much more executable virtual CPUs than available physical CPUs, still impede the synchronization operations of parallel applications, causing severe performance degradation. Existing methods optimize parallel applications by promoting the priorities of involved VMs. They cannot fully explore the performance of parallel applications, because they ignore the time-slice requirements of different phases of parallel applications. Furthermore, non-parallel applications experience unsatisfied performance because of low scheduling priorities. Given empirical analysis on time-slices of virtual machines (VMs), we find that shortening time-slices can mitigate synchronization overhead which incurs during communication phases, while over-short time-slices cause frequent cache misses in computation phases. Accordingly, we propose an Adaptive Time-slice Control (ATC) mechanism. ATC first detects the phases of parallel applications based on lock latency or cache misses. Then, ATC shortens time-slices during communication phases and prolongs time-slices during computation phases for parallel applications, and sets a uniform time-slice for non-parallel applications. We evaluate ATC using seven well-known benchmarks with 25+ applications. Experiments show that ATC obtains 1.5-75× performance gain for running parallel applications than state-of-the-art solutions, with nearly unaffected impact on non-parallel applications.

Convolutional neural networks (CNNs) are becoming more and more important for solving challenging and critical problems in many fields. CNN inference applications have been deployed in safety-critical systems, which may suffer from soft errors caused by high-energy particles, high temperature, or abnormal voltage. Of critical importance is ensuring the stability of the CNN inference process against soft errors. Traditional fault tolerance methods are not suitable for CNN inference because error-correcting code is unable to protect computational components, instruction duplication techniques incur high overhead, and existing algorithm-based fault tolerance (ABFT) techniques cannot protect all convolution implementations. In this article, we focus on how to protect the CNN inference process against soft errors as efficiently as possible, with the following three contributions. (1) We propose several systematic ABFTschemes based on checksum techniques and analyze their fault protection ability and runtime thoroughly. Unlike traditional ABFT based on matrix-matrix multiplication, our schemes support any convolution implementations. (2) We design a novel workflow integrating all the proposed schemes to obtain a high detection/correction ability with limited total runtime overhead. (3) We perform our evaluation using ImageNet with well-known CNN models including AlexNet, VGG-19, ResNet-18, and YOLOv2. Experimental results demonstrate that our implementation can handle soft errors with very limited runtime overhead (4%~8% in both error-free and error-injected situations).

Error-bounded lossy compression is a state-of-the-art data reduction technique for HPC applications because it not only significantly reduces storage overhead but also can retain high fidelity for postanalysis. Because supercomputers and HPC applications are becoming heterogeneous using accelerator-based architectures, in particular GPUs, several development teams have recently released GPU versions of their lossy compressors. However, existing state-of-the-art GPU-based lossy compressors suffer from either low compression and decompression throughput or low compression quality. In this paper, we present an optimized GPU version, cuSZ, for one of the best error-bounded lossy compressors-SZ. To the best of our knowledge, cuSZ is the first error-bounded lossy compressor on GPUs for scientific data. Our contributions are fourfold. (1) We propose a dual-quantization scheme to entirely remove the data dependency in the prediction step of SZ such that this step can be performed very efficiently on GPUs. (2) We develop an efficient customized Huffman coding for the SZ compressor on GPUs. (3) We implement cuSZ using CUDA and optimize its performance by improving the utilization of GPU memory bandwidth. (4) We evaluate our cuSZ on five real-world HPC application datasets from the Scientific Data Reduction Benchmarks and compare it with other state-of-the-art methods on both CPUs and GPUs. Experiments show that our cuSZ improves SZ's compression throughput by up to 370.1x and 13.1x, respectively, over the production version running on single and multiple CPU cores, respectively, while getting the same quality of reconstructed data. It also improves the compression ratio by up to 3.48x on the tested data compared with another state-of-the-art GPU supported lossy compressor.

The objective of this work is to develop error-bounded lossy compression methods to preserve topological features in 2D and 3D vector fields. Specifically, we explore the preservation of critical points in piecewise linear vector fields. We define the preservation of critical points as, without any false positive, false negative, or false type change in the decompressed data, (1) keeping each critical point in its original cell and (2) retaining the type of each critical point (e.g., saddle and attracting node). The key to our method is to adapt a vertex-wise error bound for each grid point and to compress input data together with the error bound field using a modified lossy compressor. Our compression algorithm can be also embarrassingly parallelized for large data handling and in situ processing. We benchmark our method by comparing it with existing lossy compressors in terms of false positive/negative/type rates, compression ratio, and various vector field visualizations with several scientific applications.

Efficient error-controlled lossy compressors are becoming critical to the success of today's large-scale scientific applications because of the ever-increasing volume of data produced by the applications. In the past decade, many lossless and lossy compressors have been developed with distinct design principles for different scientific datasets in largely diverse scientific domains. In order to support researchers and users assessing and comparing compressors in a fair and convenient way, we establish a standard compression assessment benchmark - Scientific Data Reduction Benchmark (SDRBench)1. SDRBench contains a vast variety of real-world scientific datasets across different domains, summarizes several critical compression quality evaluation metrics, and integrates many state-of-the-art lossy and lossless compressors. We demonstrate evaluation results using SDRBench and summarize six valuable takeaways that are helpful to the in-depth understanding of lossy compressors.

Data reduction techniques have been widely demanded and used by large-scale high performance computing (HPC) applications because of vast volumes of data to be produced and stored for post-analysis. Due to very limited compression ratios of lossless compressors, error-bounded lossy compression has become an indispensable part in many HPC applications nowadays, because it can significantly reduce science data volume with user-acceptable data distortion. Since the large-scale HPC applications equipped with lossy compression techniques always need to deal with vast volume of data, soft errors or silent data corruptions (SDC) are non-negligible. Although SDC detection techniques have been studied for years, no studies were performed toward the HPC applications with lossy compression, leaving a significant gap between these applications and confidence of execution results. To fill this gap, this paper proposes a couple of SDC detection strategies for scientific simulations with lossy compression. Experimental results on 4 widely used scientific simulation datasets show promising detection ability could be still obtained with two popular lossy compressors. Our parallel experiments with up to 1,024 cores confirm that the time overheads could be limited within 7.9%.

Today's extreme-scale high-performance computing (HPC) applications are producing volumes of data too large to save or transfer because of limited storage space and I/O bandwidth. Error-bounded lossy compression has been commonly known as one of the best solutions to the big science data issue, because it can significantly reduce the data volume with strictly controlled data distortion based on user requirements. In this work, we develop an adaptive parameter optimization algorithm integrated with a series of optimization strategies for SZ, a state-of-the-art prediction-based compression model. Our contribution is threefold. (1) We exploit effective strategies by using 2nd-order regression and 2nd-order Lorenzo predictors to improve the prediction accuracy significantly for SZ, thus substantially improving the overall compression quality. (2) We design an efficient approach selecting the best-fit parameter setting, by conducting a comprehensive priori compression quality analysis and exploiting an efficient online controlling mechanism. (3) We evaluate the compression quality and performance on a supercomputer with 4,096 cores, as compared with other state-of-the-art error-bounded lossy compressors. Experiments with multiple real-world HPC simulations datasets show that our solution can improve the compression ratio up to 46% compared with the second-best compressor. Moreover, the parallel I/O performance is improved by up to 40% thanks to the significant reduction of data size.

With ever-increasing volumes of scientific floating-point data being produced by high-performance computing applications, significantly reducing scientific floating-point data size is critical, and error-controlled lossy compressors have been developed for years. None of the existing scientific floating-point lossy data compressors, however, support effective fixed-ratio lossy compression. Yet fixed-ratio lossy compression for scientific floating-point data not only compresses to the requested ratio but also respects a user-specified error bound with higher fidelity. In this paper, we present FRaZ: a generic fixed-ratio lossy compression framework respecting user-specified error constraints. The contribution is twofold. (1) We develop an efficient iterative approach to accurately determine the appropriate error settings for different lossy compressors based on target compression ratios. (2) We perform a thorough performance and accuracy evaluation for our proposed fixed-ratio compression framework with multiple state-of-the-art error-controlled lossy compressors, using several real-world scientific floating-point datasets from different domains. Experiments show that FRaZ effectively identifies the optimum error setting in the entire error setting space of any given lossy compressor. While fixed-ratio lossy compression is slower than fixed-error compression, it provides an important new lossy compression technique for users of very large scientific floating-point datasets.

Error-bounded lossy compression is critical to the success of extreme-scale scientific research because of ever-increasing volumes of data produced by today's high-performance computing (HPC) applications. Not only can error-controlled lossy compressors significantly reduce the I/O and storage burden but they can retain high data fidelity for post analysis. Existing state-of-the-art lossy compressors, however, generally suffer from relatively low compression and decompression throughput (up to hundreds of megabytes per second on a single CPU core), which considerably restrict the adoption of lossy compression by many HPC applications especially those with a fairly high data production rate. In this paper, we propose a highly efficient lossy compression approach based on field programmable gate arrays (FPGAs) under the state-of-the-art lossy compression model SZ. Our contributions are fourfold. (1) We adopt a wavefront memory layout to alleviate the data dependency during the prediction for higher-dimensional predictors, such as the Lorenzo predictor. (2) We propose a co-design framework named waveSZ based on the wavefront memory layout and the characteristics of SZ algorithm and carefully implement it by using high-level synthesis. (3) We propose a hardware-algorithm co-optimization method to improve the performance. (4) We evaluate our proposed waveSZ on three real-world HPC simulation datasets from the Scientific Data Reduction Benchmarks and compare it with other state-of-the-art methods on both CPUs and FPGAs. Experiments show that our waveSZ can improve SZ's compression throughput by 6.9X ~ 8.7X over the production version running on a state-of-the-art CPU and improve the compression ratio and throughput by 2.1X and 5.8X on average, respectively, compared with the state-of-the-art FPGA design.

Scientific simulations in high-performance computing (HPC) environments generate vast volume of data, which may cause a severe I/O bottleneck at runtime and a huge burden on storage space for postanalysis. Unlike traditional data reduction schemes such as deduplication or lossless compression, not only can error-controlled lossy compression significantly reduce the data size but it also holds the promise to satisfy user demand on error control. Pointwise relative error bounds (i.e., compression errors depends on the data values) are widely used by many scientific applications with lossy compression since error control can adapt to the error bound in the dataset automatically. Pointwise relative-error-bounded compression is complicated and time consuming. We develop efficient precomputation-based mechanisms based on the SZ lossy compression framework. Our mechanisms can avoid costly logarithmic transformation and identify quantization factor values via a fast table lookup, greatly accelerating the relative-error-bounded compression with excellent compression ratios. In addition, we reduce traversing operations for Huffman decoding, significantly accelerating the decompression process in SZ. Experiments with eight well-known real-world scientific simulation datasets show that our solution can improve the compression and decompression rates (i.e., the speed) by about 40 and 80 p, respectively, in most of cases, making our designed lossy compression strategy the best-in-class solution in most cases.

Because of the ever-increasing data being produced by today's high performance computing (HPC) scientific simulations, I/O performance is becoming a significant bottleneck for their executions. An efficient error-controlled lossy compressor is a promising solution to significantly reduce data writing time for scientific simulations running on supercomputers. In this paper, we explore how to optimize the data dumping performance for scientific simulation by leveraging error-bounded lossy compression techniques. The contributions of the paper are threefold. (1) We propose a novel I/O performance profiling model that can effectively represent the I/O performance with different execution scales and data sizes, and optimize the estimation accuracy of data dumping performance using least square method. (2) We develop an adaptive lossy compression framework that can select the bestfit compressor (between two leading lossy compressors SZ and ZFP) with optimized parameter settings with respect to overall data dumping performance. (3) We evaluate our adaptive lossy compression framework with up to 32k cores on a supercomputer facilitated with fast I/O systems and using real-world scientific simulation datasets. Experiments show that our solution can mostly always lead the data dumping performance to the optimal level with very accurate selection of the bestfit lossy compressor and settings. The data dumping performance can be improved by up to 27% at different scales.

An in-depth understanding of the failure features of HPC jobs in a supercomputer is critical to the large-scale system maintenance and improvement of the service quality for users. In this paper, we investigate the features of hundreds of thousands of jobs in one of the most powerful supercomputers, the IBM Blue Gene/Q Mira, based on 2001 days of observations with a total of over 32.44 billion core-hours. We study the impact of the system's events on the jobs' execution in order to understand the system's reliability from the perspective of jobs and users. The characterization involves a joint analysis based on multiple data sources, including the reliability, availability, and serviceability (RAS) log; job scheduling log; the log regarding each job's physical execution tasks; and the I/O behavior log. We present 22 valuable takeaways based on our in-depth analysis. For instance, 99,245 job failures are reported in the job-scheduling log, a large majority (99.4%) of which are due to user behavior (such as bugs in code, wrong configuration, or misoperations). The job failures are correlated with multiple metrics and attributes, such as users/projects and job execution structure (number of tasks, scale, and core-hours). The best-fitting distributions of a failed job's execution length (or interruption interval) include Weibull, Pareto, inverse Gaussian, and Erlang/exponential, depending on the types of errors (i.e., exit codes). The RAS events affecting job executions exhibit a high correlation with users and core-hours and have a strong locality feature. In terms of the failed jobs, our similarity-based event-filtering analysis indicates that the mean time to interruption is about 3.5 days.

Today's deep neural networks (DNNs) are becoming deeper and wider because of increasing demand on the analysis quality and more and more complex applications to resolve. The wide and deep DNNs, however, require large amounts of resources (such as memory, storage, and I/O), significantly restricting their utilization on resource-constrained platforms. Although some DNN simplification methods (such as weight quantization) have been proposed to address this issue, they suffer from either low compression ratios or high compression errors, which may introduce an expensive fine-tuning overhead (i.e., a costly retraining process for the target inference accuracy). In this paper, we propose DeepSZ: an accuracy-loss expected neural network compression framework, which involves four key steps: network pruning, error bound assessment, optimization for error bound configuration, and compressed model generation, featuring a high compression ratio and low encoding time. The contribution is threefold. (1)We develop an adaptive approach to select the feasible error bounds for each layer. (2) We build a model to estimate the overall loss of inference accuracy based on the inference accuracy degradation caused by individual decompressed layers. (3) We develop an efficient optimization algorithm to determine the best-fit configuration of error bounds in order to maximize the compression ratio under the user-set inference accuracy constraint. Experiments show that DeepSZ can compress AlexNet and VGG-16 on the ImageNet dataset by a compression ratio of 46× and 116×, respectively, and compress LeNet-300-100 and LeNet-5 on the MNIST dataset by a compression ratio of 57× and 56×, respectively, with only up to 0.3% loss of inference accuracy. Compared with other state-of-the-art methods, DeepSZ can improve the compression ratio by up to 1.43×, the DNN encoding performance by up to 4.0× with four V100 GPUs, and the decoding performance by up to 6.2×.

Scientific simulations in high-performance computing (HPC) environments are producing vast volume of data, which may cause a severe I/O bottleneck at runtime and a huge burden on storage space for post-analysis. Unlike the traditional data reduction schemes (such as deduplication or lossless compression), not only can error-controlled lossy compression significantly reduce the data size but it can also hold the promise to satisfy user demand on error control. Point-wise relative error bounds (i.e., compression errors depends on the data values) are widely used by many scientific applications in the lossy compression, since error control can adapt to the precision in the dataset automatically. Point-wise relative error bounded compression is complicated and time consuming. In this work, we develop efficient precomputation-based mechanisms in the SZ lossy compression framework. Our mechanisms can avoid costly logarithmic transformation and identify quantization factor values via a fast table lookup, greatly accelerating the relative-error bounded compression with excellent compression ratios. In addition, our mechanisms also help reduce traversing operations for Huffman decoding, and thus significantly accelerate the decompression process in SZ. Experiments with four well-known real-world scientific simulation datasets show that our solution can improve the compression rate by about 30% and decompression rate by about 70% in most of cases, making our designed lossy compression strategy the best choice in class in most cases.

Introspective sorting is a ubiquitous sorting algorithm which underlies many large scale distributed systems. Hardware-mediated soft errors can result in comparison and memory errors, and thus cause introsort to generate incorrect output, which in turn disrupts systems built upon introsort; hence, it is critical to incorporate fault tolerance capability within introsort. This paper proposes the first theoretically-sound, practical fault tolerant introsort with negligible overhead: FT-iSort. To tolerate comparison errors, we use minimal TMR protection via exploiting the properties of the effects of soft errors on introsort. This algorithm-based selective protection incurs far less overhead than naïve TMR protection designed to protect an entire application. To tolerate memory errors that escape DRAM error correcting code, we propose XOR-based re-execution. We incorporate our fault tolerance method into the well-known parallel sorting implementation HykSort, and we find that fault tolerant HykSort incurs negligible overhead and obtains nearly the same scalability as unprotected HykSort.

With the ever-increasing volumes of data produced by today's large-scale scientific simulations, error-bounded lossy compression techniques have become critical: not only can they significantly reduce the data size but they also can retain high data fidelity for postanalysis. In this paper, we design a strategy to improve the compression quality significantly based on an optimized, hybrid prediction model. Our contribution is fourfold. (1) We propose a novel, transform-based predictor and optimize its compression quality. (2) We significantly improve the coefficient-encoding efficiency for the data-fitting predictor. (3) We propose an adaptive framework that can select the best-fit predictor accurately for different datasets. (4) We evaluate our solution and several existing state-of-the-art lossy compressors by running real-world applications on a supercomputer with 8,192 cores. Experiments show that our adaptive compressor can improve the compression ratio by 112~165% compared with the second-best compressor. The parallel I/O performance is improved by about 100% because of the significantly reduced data size. The total I/O time is reduced by up to 60X with our compressor compared with the original I/O time.

Quantum circuit simulations are critical for evaluating quantum algorithms and machines. However, the number of state amplitudes required for full simulation increases exponentially with the number of qubits. In this study, we leverage data compression to reduce memory requirements, trading computation time and fidelity for memory space. Specifically, we develop a hybrid solution by combining the lossless compression and our tailored lossy compression method with adaptive error bounds at each timestep of the simulation. Our approach optimizes for compression speed and makes sure that errors due to lossy compression are uncorrelated, an important property for comparing simulation output with physical machines. Experiments show that our approach reduces the memory requirement of simulating the 61-qubit Grover's search algorithm from 32 exabytes to 768 terabytes of memory on Argonne's Theta supercomputer using 4,096 nodes. The results suggest that our techniques can increase the simulation size by 2~16 qubits for general quantum circuits.

In this paper, we explore potential correlations of fatal system events for one of the most powerful supercomputers-IBM Blue Gene/Q Mira, which is deployed at Argonne National Laboratory, based on its 5-year reliability, availability, and serviceability (RAS) log. Our contribution is two-fold. (1) We design an efficient log analysis tool, namely LogAider, with a novel filtering method to effectively extract fatal events from masses of system messages that are heavily duplicated in the log. LogAider exhibits a very precise detection of temporal-correlation with a high similarity (up to 95 percent) to the ground-truth (i.e., compared to the failure records reported by the administrators). The total number of fatal events can be reduced to about 1,255 compared with originally 2.6 million duplicated fatal messages. (2) We analyze the 5-year RAS log of the MIRA system using LogAider, and summarize six important “takeaways” which can help system vendors and administrators better understand an extreme-scale system's fatal events. Specifically, we find that the distribution or proportion of the fatal system events follow a Pareto-like principle in general. The temporal correlation among fatal events is much stronger than that of warn messages and info messages, and the correlated events tend to constitute a few clusters. The mean time between fatal events (MTBFE) of the Mira system is about 1.3 days from the perspective of the system, and the MTTI is 2-4 days from the perspective of users. The most error-prone item value with respect to any key attribute appears likely in the log every 2-10 days. Weibull, Gamma, and Pearson6 are the three best-fit distributions for the fatal event intervals. The overall correlation of fatal events on the 5D torus network is not prominent, whereas the small-region locality correlation (e.g., the fatal events inside racks) is relatively strong. We believe our work will be interesting to large-scale HPC system administrators and vendors and to fault tolerance researchers, enabling them to better understand fatal events and mitigate such events accordingly.

An effective data compressor is becoming increasingly critical to today's scientific research, and many lossy compressors are developed in the context of absolute error bounds. Based on physical/chemical definitions of simulation fields or multiresolution demand, however, many scientific applications need to compress the data with a pointwise relative error bound (i.e., the smaller the data value, the smaller the compression error to tolerate). To this end, we propose two optimized lossy compression strategies under a state-of-the-art three-staged compression framework (prediction + quantization + entropy-encoding). The first strategy (called block-based strategy) splits the data set into many small blocks and computes an absolute error bound for each block, so it is particularly suitable for the data with relatively high consecutiveness in space. The second strategy (called multi-threshold-based strategy) splits the whole value range into multiple groups with exponentially increasing thresholds and performs the compression in each group separately, which is particularly suitable for the data with a relatively large value range and spiky value changes. We implement the two strategies rigorously and evaluate them comprehensively by using two scientific applications which both require lossy compression with point-wise relative error bound. Experiments show that the two strategies exhibit the best compression qualities on different types of data sets respectively. The compression ratio of our lossy compressor is higher than that of other state-of-the-art compressors by 17.2-618 percent on the climate simulation data and 30-210 percent on the N-body simulation data, with the same relative error bound and without degradation of the overall visualization effect of the entire data.

With ever-increasing volumes of scientific data produced by high-performance computing applications, significantly reducing data size is critical because of limited capacity of storage space and potential bottlenecks on I/O or networks in writing/reading or transferring data. SZ and ZFP are two leading BSD licensed open source C/C++ libraries for compressed floating-point arrays that support high throughput read and write random access. However, their performance is not consistent across different data sets and across different fields of some data sets, which raises the need for an automatic online (during compression) selection between SZ and ZFP, with minimal overhead. In this paper, the automatic selection optimizes the rate-distortion, an important statistical quality metric based on the signal-to-noise ratio. To optimize for rate-distortion, we investigate the principles of SZ and ZFP. We then propose an efficient online, low-overhead selection algorithm that predicts the compression quality accurately for two compressors in early processing stages and selects the best-fit compressor for each data field. We implement the selection algorithm into an open-source library, and we evaluate the effectiveness of our proposed solution against plain SZ and ZFP in a parallel environment with 1,024 cores. Evaluation results on three data sets representing about 100 fields show that our selection algorithm improves the compression ratio up to 70 percent with the same level of data distortion because of very accurate selection (around 99 percent) of the bestfit compressor, with little overhead (less than 7 percent in the experiments).

Today's N-body simulations are producing extremely large amounts of data. The Hardware/Hybrid Accelerated Cosmology Code (HACC), for example, may simulate trillions of particles, producing tens of petabytes of data to store in a parallel file system, according to the HACC users. In this paper, we design and implement an efficient, in situ error-bounded lossy compressor to significantly reduce the data size for N-body simulations. Not only can our compressor save significant storage space for N-body simulation researchers, but it can also improve the I/O performance considerably with limited memory and computation overhead. Our contribution is threefold. (1) We propose an efficient data compression model by leveraging the consecutiveness of the cosmological data in both space and time dimensions as well as the physical correlation across different fields. (2) We propose a lightweight, efficient alignment mechanism to align the disordered particles across adjacent snapshots in the simulation, which is a fundamental step in the whole compression procedure. We also optimize the compression quality by exploring best-fit data prediction strategies and optimizing the frequencies of the space-based compression vs. time-based compression. (3) We evaluate our compressor using both a cosmological simulation package and molecular dynamics simulation data-two major categories in the N-body simulation domain. Experiments show that under the same distortion of data, our solution produces up to 43% higher compression ratios on the velocity field and up to 300% higher on the position field than do other state-of-the-art compressors (including SZ, ZFP, NUMARCK, and decimation). With our compressor, the overall I/O time on HACC data is reduced by up to 20% compared with the second-best compressor.

Today's scientific simulations require a significant reduction of the data size because of extremely large volumes of data they produce and the limitation of storage bandwidth and space. If the compression is set to reach a high compression ratio, however, the reconstructed data are often distorted too much to tolerate. In this paper, we explore a new compression strategy that can effectively control the data distortion when significantly reducing the data size. The contribution is threefold. (1) We propose an adaptive compression framework to select either our improved Lorenzo prediction method or our optimized linear regression method dynamically in different regions of the dataset. (2) We explore how to select them accurately based on the data features in each block to obtain the best compression quality. (3) We analyze the effectiveness of our solution in details using four real-world scientific datasets with 100+ fields. Evaluation results confirm that our new adaptive solution can significantly improve the rate distortion for the lossy compression with fairly high compression ratios. The compression ratio of our compressor is 1.5X~8X as high as that of two other leading lossy compressors (SZ and ZFP) with the same peak single-to-noise ratio (PSNR), in the high-compression cases. Parallel experiments with 8,192 cores and 24 TB of data shows that our solution obtains 1.86X dumping performance and 1.95X loading performance compared with the second-best lossy compressor, respectively.

Computation of two-electron repulsion integrals is the critical and the most time-consuming step in a typical parallel quantum chemistry simulation. Such calculations have massive computing and storage requirements, which scale as O(N^4) with the size of a chemical system. Compressing the integral's data and storing it on disk can avoid costly recalculation, significantly speeding the overall quantum chemistry calculations; but it requires a fast compression algorithm. To this end, we developed PaSTRI (Pattern Scaling for Two-electron Repulsion Integrals) and implemented the algorithm in the data compression package SZ. PaSTRI leverages the latent pattern features in the integral dataset and optimizes the calculation of the appropriate number of bits required for the storage of the integral. We have evaluated PaSTRI using integral datasets generated by the quantum chemistry program GAMESS. The results show an excellent 16.8 compression ratio with low overhead, while maintaining 10-10absolute precision based on user's requirement.

Because of the ever-increasing execution scale of scientific applications, how to store the extremely large volume of data efficiently is becoming a serious issue. A significant reduction of the scientific data size can effectively mitigate the I/O burden and save considerable storage space. Since lossless compressors suffer from limited compression ratios, error-controlled lossy compressors have been studied for years. Existing error-controlled lossy compressors, however, focus mainly on absolute error bounds, which cannot meet users' diverse demands such as pointwise relative error bounds. Although some of the state-of-the-art lossy compressors support pointwise relative error bound, the compression ratios are generally low because of the limitation in their designs and possible spiky data changes in local data regions. In this work, we propose a novel, efficient approach to perform compression based on the pointwise relative error bound with higher compression ratios than existing solutions provide. Our contribution is threefold. (1) We propose a novel transformation scheme that can transfer the pointwise relative-error-bounded compression problem to an absolute-error-bounded compression issue. We also analyze the practical properties of our transformation scheme both theoretically and experimentally. (2) We implement the proposed technique in two of the most popular absolute-error-bounded lossy compressors, SZ and ZFP. (3) We evaluate our solution using multiple real-world application data across different scientific domains on a supercomputer with up to 4,096 cores and 12 TB of data. Experiments show that our solution achieves over 1.38X dumping and 1.31X loading performance over the second-best lossy compressor, respectively.

Error-controlled lossy compression has been studied for years because of extremely large volumes of data being produced by today's scientific simulations. None of existing lossy compressors, however, allow users to fix the peak signal-to-noise ratio (PSNR) during compression, although PSNR has been considered as one of the most significant indicators to assess compression quality. In this paper, we propose a novel technique providing a fixed-PSNR lossy compression for scientific data sets. We implement our proposed method based on the SZ lossy compression framework and release the code as an open-source toolkit. We evaluate our fixed-PSNR compressor on three realworld high-performance computing data sets. Experiments show that our solution has a high accuracy in controlling PSNR, with an average deviation of 0.1 ~ 5.0 dB on the tested data sets.

With the growing computational complexity of science and the complexity of new and emerging hardware, it is time to re-evaluate the traditional monolithic design of computational codes. One new paradigm is constructing larger scientific computational experiments from the coupling of multiple individual scientific applications, each targeting their own physics, characteristic lengths, and/or scales. We present a framework constructed by leveraging capabilities such as in-memory communications, workflow scheduling on HPC resources, and continuous performance monitoring. This code coupling capability is demonstrated by a fusion science scenario, where differences between the plasma at the edges and at the core of a device have different physical descriptions. This infrastructure not only enables the coupling of the physics components, but it also connects in situ or online analysis, compression, and visualization that accelerate the time between a run and the analysis of the science content. Results from runs on Titan and Cori are presented as a demonstration.

Iterative methods are commonly used approaches to solve large, sparse linear systems, which are fundamental operations for many modern scientific simulations. When the large-scale iterative methods are running with a large number of ranks in parallel, they have to checkpoint the dynamic variables periodically in case of unavoidable fail-stop errors, requiring fast I/O systems and large storage space. To this end, significantly reducing the checkpointing overhead is critical to improving the overall performance of iterative methods. Our contribution is fourfold. (1) We propose a novel lossy checkpointing scheme that can significantly improve the checkpointing performance of iterative methods by leveraging lossy compressors. (2) We formulate a lossy checkpointing performance model and derive theoretically an upper bound for the extra number of iterations caused by the distortion of data in lossy checkpoints, in order to guarantee the performance improvement under the lossy checkpointing scheme. (3) We analyze the impact of lossy checkpointing (i.e., extra number of iterations caused by lossy checkpointing files) for multiple types of iterative methods. (4) We evaluate the lossy checkpointing scheme with optimal checkpointing intervals on a high-performance computing environment with 2,048 cores, using a well-known scientific computation package PETSc and a state-of-the-art checkpoint/restart toolkit. Experiments show that our optimized lossy checkpointing scheme can significantly reduce the fault tolerance overhead for iterative methods by 23%∼70% compared with traditional checkpointing and 20%∼58% compared with lossless-compressed checkpointing, in the presence of system failures.

GPUs have been increasingly used to accelerate graph processing for complicated computational problems regarding graph theory. Many parallel graph algorithms adopt the asynchronous computing model to accelerate the iterative convergence. Unfortunately, the consistent asynchronous computing requires locking or atomic operations, leading to significant penalties/overheads when implemented on GPUs. As such, the coloring algorithm is adopted to separate the vertices with potential updating conflicts, guaranteeing the consistency/correctness of the parallel processing. Common coloring algorithms, however, may suffer from low parallelism because of a large number of colors generally required for processing a large-scale graph with billions of vertices. We propose a light-weight asynchronous processing framework called Frog with a preprocessing/hybrid coloring model. The fundamental idea is based on the Pareto principle (or 80-20 rule) about coloring algorithms as we observed through masses of real-world graph coloring cases. We find that a majority of vertices (about 80 percent) are colored with only a few colors, such that they can be read and updated in a very high degree of parallelism without violating the sequential consistency. Accordingly, our solution separates the processing of the vertices based on the distribution of colors. In this work, we mainly answer three questions: (1) how to partition the vertices in a sparse graph with maximized parallelism, (2) how to process large-scale graphs that cannot fit into GPU memory, and (3) how to reduce the overhead of data transfers on PCIe while processing each partition. We conduct experiments on real-world data (Amazon, DBLP, YouTube, RoadNet-CA, WikiTalk, and Twitter) to evaluate our approach and make comparisons with well-known non-preprocessed (such as Totem, Medusa, MapGraph, and Gunrock) and preprocessed (Cusha) approaches, by testing four classical algorithms (BFS, PageRank, SSSP, and CC). On all the tested applications and datasets, Frog is able to significantly outperform existing GPU-based graph processing systems except Gunrock and MapGraph. MapGraph gets better performance than Frog when running BFS on RoadNet-CA. The comparison between Gunrock and Frog is inconclusive. Frog can outperform Gunrock more than 1.04X when running PageRank and SSSP, while the advantage of Frog is not obvious when running BFS and CC on some datasets especially for RoadNet-CA.

Since today's scientific applications are producing vast amounts of data, compressing them before storage/transmission is critical. Results of existing compressors show two types of HPC data sets: highly compressible and hard to compress. In this work, we carefully design and optimize the error-bounded lossy compression for hard-to-compress scientific data. We propose an optimized algorithm that can adaptively partition the HPC data into best-fit consecutive segments each having mutually close data values, such that the compression condition can be optimized. Another significant contribution is the optimization of shifting offset such that the XOR-leading-zero length between two consecutive unpredictable data points can be maximized. We finally devise an adaptive method to select the best-fit compressor at runtime for maximizing the compression factor. We evaluate our solution using 13 benchmarks based on real-world scientific problems, and we compare it with 9 other state-of-the-art compressors. Experiments show that our compressor can always guarantee the compression errors within the user-specified error bounds. Most importantly, our optimization can improve the compression factor effectively, by up to 49 percent for hard-to-compress data sets with similar compression/ decompression time cost.

Nowadays, by integrating the cloud radio access network (C-RAN) with the mobile edge cloud computing (MEC) technology, mobile service provider (MSP) can efficiently handle the increasing mobile traffic and enhance the capabilities of mobile devices. But the power consumption has become skyrocketing for MSP and it gravely affects the profit of MSP. Previous work often studied the power consumption in C-RAN and MEC separately while less work had considered the integration of C-RAN with MEC. In this paper, we present an unifying framework for the power-performance tradeoff of MSP by jointly scheduling network resources in C-RAN and computation resources in MEC to maximize the profit of MSP. To achieve this objective, we formulate the resource scheduling issue as a stochastic problem and design a new optimization framework by using an extended Lyapunov technique. Specially, because the standard Lyapunov technique critically assumes that job requests have fixed lengths and can be finished within each decision making interval, it is not suitable for the dynamic situation where the mobile job requests have variable lengths. To solve this problem, we extend the standard Lyapunov technique and design the VariedLen algorithm to make online decisions in consecutive time for job requests with variable lengths. Our proposed algorithm can reach time average profit that is close to the optimum with a diminishing gap (1/V) for the MSP while still maintaining strong system stability and low congestion. With extensive simulations based on a real world trace, we demonstrate the efficacy and optimality of our proposed algorithm.

In situ lossy compression allowing user-controlled data loss can significantly reduce the I/O burden. For large-scale N-body simulations where only one snapshot can be compressed at a time, the lossy compression ratio is very limited because of the fairly low spatial coherence of the particle data. In this work, we assess the state-of-the-art single-snapshot lossy compression techniques of two common N-body simulation models: cosmology and molecular dynamics. We design a series of novel optimization techniques based on the two representative real-world N-body simulation codes. For molecular dynamics simulation, we propose three compression modes (i.e., best speed, best tradeoff, best compression mode) that can refine the tradeoff between the compression rate (a.k.a., speed/throughput) and ratio. For cosmology simulation, we identify that our improved SZ is the best lossy compressor with respect to both compression ratio and rate. Its compression ratio is higher than the second-best compressor by 11% with comparable compression rate. Experiments with up to 1024 cores on the Blues supercomputer at Argonne show that our proposed lossy compression method can reduce I/O time by 80% compared with writing data directly to a parallel file system and outperforms the second-best solution by 60%. Moreover, our proposed lossy compression methods have the best rate-distortion with reasonable compression errors on the tested N-body simulation data compared with state-of-the-art compressors.

Today's large-scale supercomputers are producing a huge amount of log data. Exploring various potential correlations of fatal events is crucial for understanding their causality and improving the working efficiency for system administrators. To this end, we developed a toolkit, named LogAider, that can reveal three types of potential correlations: across-field, spatial, and temporal. Across-field correlation refers to the statistical correlation across fields within a log or across multiple logs based on probabilistic analysis. For analyzing the spatial correlation of events, we developed a generic, easy-to-use visualizer that can view any events queried by userson a system machine graph. LogAider can also mine spatial correlations by an optimized K-meaning clustering algorithm over a Torus network topology. It is also able to disclose the temporal correlations (or error propagations) over a certain period inside a log or across multiple logs, based on an effective similarity analysis strategy. We assessed LogAider using theone-year reliability-availability-serviceability (RAS) log of Mira system (one of the world's most powerful supercomputers), as well as its job log. We find that LogAider very helpful for revealing the potential correlations of fatal system events and job events, with an accurate mining of across-field correlation with both precision and recall of 99.9-100%, as well as precisedetection of temporal-correlation with a high similarity (up to 95%) to the ground-truth.

Future high-performance computing (HPC) systems with ever-increasing resource capacity (such as compute cores, memory and storage) may significantly increase the risks on reliability. Silent data corruptions (SDCs) or silent errors are among the major sources that corrupt HPC execution results. Unlike fail-stop errors, SDCs can be harmful and dangerous in that they cannot be detected by hardware. To remedy this, we propose an online MAchine-learning-based silent data CORruption Detection framework (abbreviated as MACORD) for detecting SDCs in HPC applications. In our study, we comprehensively investigate the prediction ability of a multitude of machine-learning algorithms and enable the detector to automatically select the best-fit algorithms at runtime to adapt to the data dynamics. Because it takes only spatial features (i.e., neighboring data values for each data point in the current time step) into the training data, our learning framework exhibits low memory overhead (less than 1%). Experiments based on real-world scientific applications/benchmarks show that our framework can elevate the detection sensitivity (i.e., recall) up to 99%. Meanwhile the false positive rate is limited to 0.1% in most cases, which is one order of magnitude improvement compared with the latest state-of-the-art spatial technique.

A practical problem facing Infrastructure-as-a-Service (IaaS) cloud users is how to minimize their costs by choosing different pricing options based on their own demands. Recently, cloud brokerage service is introduced to tackle this problem. But due to the perishability of cloud resources, there still exists a large amount of idle resource waste during the reservation period of reserved instances. This idle resource waste problem is challenging cloud broker when buying reserved instances to accommodate users' job requests. To solve this challenge, we find that cloud users always have low priority jobs (e.g., non latency-sensitive jobs) which can be delayed to utilize these idle resources. With considering the priority of jobs, two problems need to be solved. First, how can cloud broker leverage jobs' priorities to reserve resources for profit maximization? Second, how to fairly price users' job requests with different priorities when previous studies either adopt pricing schemes from IaaS clouds or just ignore the pricing issue. To solve these problems, we first design a fair and priority aware pricing scheme, PriorityPricing, for the broker which charges users with different prices based on priorities. Then we propose three dynamic algorithms for the broker to make resource reservations with the objective of maximizing its profit. Experiments show that the broker's profit can be increased up to 2.5× than that without considering priority for offline algorithm, and 3.7× for online algorithm.

Today's HPC applications are producing extremely large amounts of data, such that data storage and analysis are becoming more challenging for scientific research. In this work, we design a new error-controlled lossy compression algorithm for large-scale scientific data. Our key contribution is significantly improving the prediction hitting rate (or prediction accuracy) for each data point based on its nearby data values along multiple dimensions. We derive a series of multilayer prediction formulas and their unified formula in the context of data compression. One serious challenge is that the data prediction has to be performed based on the preceding decompressed values during the compression in order to guarantee the error bounds, which may degrade the prediction accuracy in turn. We explore the best layer for the prediction by considering the impact of compression errors on the prediction accuracy. Moreover, we propose an adaptive error-controlled quantization encoder, which can further improve the prediction hitting rate considerably. The data size can be reduced significantly after performing the variable-length encoding because of the uneven distribution produced by our quantization encoder. We evaluate the new compressor on production scientific data sets and compare it with many other state-of-the-art compressors: GZIP, FPZIP, ZFP, SZ-1.1, and ISABELA. Experiments show that our compressor is the best in class, especially with regard to compression factors (or bit-rates) and compression errors (including RMSE, NRMSE, and PSNR). Our solution is better than the second-best solution by more than a 2x increase in the compression factor and 3.8x reduction in the normalized root mean squared error on average, with reasonable error bounds and user-desired bit-rates.

Silent data corruption (SDC) poses a great challenge for high-performance computing (HPC) applications as we move to extreme-scale systems. Mechanisms have been proposed that are able to detect SDC in HPC applications by using the peculiarities of the data (more specifically, its “smoothness” in time and space) to make predictions. However, these data-analytic solutions are still far from fully protecting applications to a level comparable with more expensive solutions such as full replication. In this work, we propose partial replication to overcome this limitation. More specifically, we have observed that not all processes of an MPI application experience the same level of data variability at exactly the same time. Thus, we can smartly choose and replicate only those processes for which the lightweight data-analytic detectors would perform poorly. In addition, we propose a new evaluation method based on the probability that a corruption will pass unnoticed by a particular detector (instead of just reporting overall single-bit precision and recall). In our experiments, we use four applications dealing with different explosions. Our results indicate that our new approach can protect the MPI applications analyzed with 7-70 percent less overhead (depending on the application) than that of full duplication with similar detection recall.

The traditional single-level checkpointing method suffers from significant overhead on large-scale platforms. Hence, multilevel checkpointing protocols have been studied extensively in recent years. The multilevel checkpoint approach allows different levels of checkpoints to be set (each with different checkpoint overheads and recovery abilities), in order to further improve the fault tolerance performance of extreme-scale HPC applications. How to optimize the checkpoint intervals for each level, however, is an extremely difficult problem. In this paper, we construct an easy-to-use two-level checkpoint model. Checkpoint level 1 deals with errors with low checkpoint/recovery overheads such as transient memory errors, while checkpoint level 2 deals with hardware crashes such as node failures. Compared with previous optimization work, our new optimal checkpoint solution offers two improvements: (1) it is an online solution without requiring knowledge of the job length in advance, and (2) it shows that periodic patterns are optimal and determines the best pattern. We evaluate the proposed solution and compare it with the most up-to-date related approaches on an extreme-scale simulation testbed constructed based on a real HPC application execution. Simulation results show that our proposed solution outperforms other optimized solutions and can improve the performance significantly in some cases. Specifically, with the new solution the wall-clock time can be reduced by up to 25.3 percent over that of other state-of-the-art approaches. Finally, a brute-force comparison with all possible patterns shows that our solution is always within 1 percent of the best pattern in the experiments.

In virtualized data centers, virtual disk images (VDIs) serve as the containers in virtual environment, so their access performance is critical for the overall system performance. Some distributed VDI chunk storage systems have been proposed in order to alleviate the I/O bottleneck for VM management. As the system scales up to a large number of running VMs, however, the overall network traffic would become unbalanced with hot spots on some VMs inevitably, leading to I/O performance degradation when accessing the VMs. In this paper, we propose an adaptive and collaborative VDI storage system (ACStor) to resolve the above performance issue. In comparison with the existing research, our solution is able to dynamically balance the traffic workloads in accessing VDI chunks, based on the run-time network state. Specifically, compute nodes with lightly loaded traffic will be adaptively assigned more chunk access requests from remote VMs and vice versa, which can effectively eliminate the above problem and thus improves the I/O performance of VMs. We implement a prototype based on our ACStor design, and evaluate it by various benchmarks on a real cluster with 32 nodes and a simulated platform with 256 nodes. Experiments show that under different network traffic patterns of data centers, our solution achieves up to 2-8× performance gain on VM booting time and VM's I/O throughput, in comparison with the other state-of-the-art approaches.

As the exascale era approaches, the increasing capacity of high-performance computing (HPC) systems with targeted power and energy budget goals introduces significant challenges in reliability. Silent data corruptions (SDCs) or silent errors are one of the major sources that corrupt the executionresults of HPC applications without being detected. In this work, we explore a low-memory-overhead SDC detector, by leveraging epsilon-insensitive support vector machine regression, to detect SDCs that occur in HPC applications that can be characterized by an impact error bound. The key contributions are three fold. (1) Our design takes spatialfeatures (i.e., neighbouring data values for each data point in a snapshot) into training data, such that little memory overhead (less than 1%) is introduced. (2) We provide an in-depth study on the detection ability and performance with different parameters, and we optimize the detection range carefully. (3) Experiments with eight real-world HPC applications show thatour detector can achieve the detection sensitivity (i.e., recall) up to 99% yet suffer a less than 1% of false positive rate for most cases. Our detector incurs low performance overhead, 5% on average, for all benchmarks studied in the paper. Compared with other state-of-the-art techniques, our detector exhibits the best tradeoff considering the detection ability and overheads.

Today's HPC applications are producing extremely large amounts of data, thus it is necessary to use an efficient compression before storing them to parallel file systems. In this paper, we optimize the error-bounded HPC data compression, by proposing a novel HPC data compression method that works very effectively on compressing large-scale HPC data sets. The compression method starts by linearizing multi-dimensional snapshot data. The key idea is to fit/predict the successive data points with the bestfit selection of curve fitting models. The data that can be predicted precisely will be replaced by the code of the corresponding curve-fitting model. As for the unpredictable data that cannot be approximated by curve-fitting models, we perform an optimized lossy compression via a binary representation analysis. We evaluate our proposed solution using 13 real-world HPC applications across different scientific domains, and compare it to many other state-of-the-art compression methods (including Gzip, FPC, ISABELA, NUMARCK, ZFP, FPZIP, etc.). Experiments show that the compression ratio of our compressor ranges in 3.3/1 - 436/1, which is higher than the second-best solution ZFP by as little as 2x and as much as an order of magnitude for most cases. The compression time of SZ is comparable to other solutions', while its decompression time is less than the second best one by 50%-90%. On an extreme-scale use case, experiments show that the compression ratio of SZ exceeds that of ZFP by 80%.

Tightly-coupled parallel applications in cloud systems may suffer from significant performance degradation because of the resource over-commitment issue. In this paper, we propose a dynamic approach based on the adaptive control over time-slice for virtual clusters, in order to mitigate the performance degradation for parallel applications in cloud and avoid the negative impact effectively on other non-parallel applications meanwhile. The key idea is to reduce the synchronization overhead inside and across virtual machines (VMs) in cloud systems, by dynamically adjusting the time-slices of VMs in terms of the spinlock latency at runtime. Such a design is motivated by our experimental finding that VM's time slice is a key factor determining the synchronization overhead as well as the parallel execution performance. We perform the evaluation on a real cluster environment deployed with XEN, using five well-known benchmarks with 10+ applications. Experiments show that our approach obtains 1.5-10× performance gain for running parallel applications, than other state-of-the-art solutions (including Credit Scheduling of Xen and the well-known methods like Co-Scheduling and Balance Scheduling), with nearly unaffected impact on the performance of non-parallel applications.

Nowadays, by integrating the cloud radio access network (C-RAN) with the mobile cloud computing (MCC) technology, mobile service provider (MSP) can efficiently handle the increasing mobile traffic and enhance the capabilities of mobile users' devices to provide better quality of service (QoS). But the power consumption has become skyrocketing for MSP as it gravely affects the profit of MSP. Previous work often studied the power consumption in C-RAN and MCC separately while less work had considered the integration of C-RAN with MCC. In this paper, we present a unifying framework for optimizing the power-performance tradeoff of MSP by jointly scheduling network resources in C-RAN and computation resources in MCC to minimize the power consumption of MSP while still guaranteeing the QoS for mobile users. Our objective is to maximize the profit of MSP. To achieve this objective, we first formulate the resource scheduling issue as a stochastic problem and then propose a Resource onlIne sCHeduling (RICH) algorithm using Lyapunov optimization technique to approach a time average profit that is close to the optimum with a diminishing gap (1/V) for MSP while still maintaining strong system stability and low congestion to guarantee the QoS for mobile users. With extensive simulations, we demonstrate that the profit of RICH algorithm is 3.3× (18.4×) higher than that of active (random) algorithm.

For exascale HPC applications, silent data corruption (SDC) is one of the most dangerous problems because there is no indication that there are errors during the execution. We propose an adaptive impact-driven method that can detect SDCs dynamically. The key contributions are threefold. (1) We carefully characterize 18 HPC applications/benchmarks and discuss the runtime data features, as well as the impact of the SDCs on their execution results. (2) We propose an impact-driven detection model that does not blindly improve the prediction accuracy, but instead detects only influential SDCs to guarantee user-acceptable execution results. (3) Our solution can adapt to dynamic prediction errors based on local runtime data and can automatically tune detection ranges for guaranteeing low false alarms. Experiments show that our detector can detect 80-99.99 percent of SDCs with a false alarm rate less that 1 percent of iterations for most cases. The memory cost and detection overhead are reduced to 15 and 6.3 percent, respectively, for a large majority of applications.

The silent data corruption (SDC) problem is attracting more and more attentions because it is expected to have a great impact on exascale HPC applications. SDC faults are hazardous in that they pass unnoticed by hardware and can lead to wrong computation results. In this work, we formulate SDC detection as a runtime one-step-ahead prediction method, leveraging multiple linear prediction methods in order to improve the detection results. The contributions are twofold: (1) we propose an error feedback control model that can reduce the prediction errors for different linear prediction methods, and (2) we propose a spatial-data-based even-sampling method to minimize the detection overheads (including memory and computation cost). We implement our algorithms in the fault tolerance interface, a fault tolerance library with multiple checkpoint levels, such that users can conveniently protect their HPC applications against both SDC errors and fail-stop errors. We evaluate our approach by using large-scale traces from well-known, large-scale HPC applications, as well as by running those HPC applications on a real cluster environment. Experiments show that our error feedback control model can improve detection sensitivity by 34-189% for bit-flip memory errors injected with the bit positions in the range [20,30], without any degradation on detection accuracy. Furthermore, memory size can be reduced by 33% with our spatial-data even-sampling method, with only a slight and graceful degradation in the detection sensitivity.

Next-generation supercomputers are expected to have more components and, at the same time, consume several times less energy per operation. Consequently, the number of soft errors is expected to increase dramatically in the coming years. In this respect, techniques that leverage certain properties of iterative HPC applications (such as the smoothness of the evolution of a particular dataset) can be used to detect silent errors at the application level. In this paper, we present a pointwise detection model with two phases: one involving the prediction of the next expected value in the time series for each data point, and another determining a range (i.e., normal value interval) surrounding the predicted next-step value. We show that dataset correlation can be used to detect corruptions indirectly and limit the size of the data set to monitor, taking advantage of the underlying physics of the simulation. Our results show that, using our techniques, we can detect a large number of corruptions (i.e., above 90% in some cases) with 84% memory overhead, and 13.75% extra computation time.

Modern GPUs have been widely used to accelerate the graph processing for complicated computational problems regarding graph theory. Many parallel graph algorithms adopt the asynchronous computing model to accelerate the iterative convergence. Unfortunately, the consistent asynchronous computing requires locking or the atomic operations, leading to significant penalties/overheads when implemented on GPUs. To this end, coloring algorithm is adopted to separate the vertices with potential updating conflicts, guaranteeing the consistency/correctness of the parallel processing. We propose a light-weight asynchronous processing framework called Frog with a hybrid coloring model. We find that majority of vertices (about 80%) are colored with only a few colors, such that they can be read and updated in a very high degree of parallelism without violating the sequential consistency. Accordingly, our solution will separate the processing of the vertices based on the distribution of colors.

Summary In 2011, Google released a 1‐month production trace with hundreds of thousands of jobs running across over 12,000 heterogeneous hosts. In order to perform in‐depth research based on the trace, it is necessary to construct a close‐to‐practice simulation system. In this paper, we devise a distributed cloud simulator (or toolkit) based on virtual machines, with three important features. (1) The dynamic changing resource amounts (such as CPU rate and memory size) consumed by the reproduced jobs can be emulated as closely as possible to the real values in the trace. (2) Various types of events (e.g., kill/evict event) can be emulated precisely based on the trace. (3) Our simulation toolkit is able to emulate more complex and useful cases beyond the original trace to adapt to various research demands. We evaluate the system on a real cluster environment with 16×8=128 cores and 112 virtual machines constructed by XEN hypervisor. To the best of our knowledge, this is the first work to reproduce Google cloud environment with real experimental system setting and real‐world large scale production trace. Experiments show that our simulation system could effectively reproduce the real checkpointing/restart events based on Google trace, by leveraging Berkeley Lab Checkpoint/Restart tool. It can simultaneously process up to 1200 emulated Google jobs over the 112 virtual machines. Such a simulation toolkit has been released as a GNU GPL v3 software for free downloading, and it has been successfully applied to the fundamental research on the optimization of checkpoint intervals for Google tasks. Copyright © 2014 © Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

By leveraging virtual machine (VM) technology, we optimize cloud system performance based on refined resource allocation, in processing user requests with composite services. Our contribution is three-fold. (1) We devise a VM resource allocation scheme with a minimized processing overhead for task execution. (2) We comprehensively investigate the best-suited task scheduling policy with different design parameters. (3) We also explore the best-suited resource sharing scheme with adjusteddivisible resource fractions on running tasks in terms of Proportional-share model (PSM), which can be split into absolute mode (called AAPSM) and relative mode (RAPSM). We implement a prototype system over a cluster environment deployed with 56 real VM instances, and summarized valuable experience from our evaluation. As the system runs in short supply, lightest workload first (LWF) is mostly recommended because it can minimize the overall response extension ratio (RER) for both sequential-mode tasks and parallel-mode tasks. In a competitive situation with over-commitment of resources, the best one is combining LWF with both AAPSM and RAPSM. It outperforms other solutions in the competitive situation, by 16 + % w.r.t. the worst-case response time and by 7.4 + % w.r.t. the fairness.

Although many pricing schemes in IaaS platform are already proposed with pay-as-you-go and subscription/spot market policy to guarantee service level agreement, it is still inevitable to suffer from wasteful payment because of coarse-grained pricing scheme. In this paper, we investigate an optimized fine-grained and fair pricing scheme. Two tough issues are addressed: (1) the profits of resource providers and customers often contradict mutually; (2) VM-maintenance overhead like startup cost is often too huge to be neglected. Not only can we derive an optimal price in the acceptable price range that satisfies both customers and providers simultaneously, but we also find a best-fit billing cycle to maximize social welfare (i.e., the sum of the cost reductions for all customers and the revenue gained by the provider). We carefully evaluate the proposed optimized fine-grained pricing scheme with two large-scale real-world production traces (one from Grid Workload Archive and the other from Google data center). We compare the new scheme to classic coarse-grained hourly pricing scheme in experiments and find that customers and providers can both benefit from our new approach. The maximum social welfare can be increased up to 72.98 and 48.15 percent with respect to DAS-2 trace and Google trace respectively.

Due to high flexibility and cost-effectiveness, cloud computing is increasingly being explored as an alternative to local clusters by academic and commercial users. Recent research already confirmed the feasibility of running tightly-coupled parallel applications with virtual clusters. However, such types of applications suffer from significant performance degradation, especially as the over-commitment is common in cloud. That is, the number of executable Virtual CPUs (VCPUs) is often larger than that of available Physical CPUs (PCPUs) in the system. The performance degradation is mainly due to the fact that the current virtual machine monitors (VMMs) are unaware of the synchronization requirements of the VMs which are running parallel applications. In this paper, There are two key contributions. (1) We propose an autonomous synchronization-aware VM scheduling (SVS) algorithm, which can effectively mitigate the performance degradation of tightly-coupled parallel applications running atop them in over-committed situation. (2) We integrate the SVS algorithm into Xen VMM scheduler, and rigorously implement a prototype. We evaluate our design on a real cluster environment with NPB benchmark and real-world trace. Experiments show that our solution attains better performance for tightly-coupled parallel applications than the state-of-the-art approaches like Xen's Credit scheduler, balance scheduling, and hybrid scheduling.

The scale of cloud services keeps increasing over time, significantly introducing huge challenges in system manageability and reliability. Designing coordination services in cloud is the right track to solve the above problems. However, existing coordination services (e.g., Chubby and ZooKeeper) only perform well in read-intensive scenario and small ensemble scales. To this end, we propose Giraffe, a scalable distributed coordination service. There are three important contributions in our design. (1) Giraffe organizes coordination servers using interior-node-disjoint trees for better scalability. (2) Giraffe employs a novel Paxos protocol for strong consistency and fault-tolerance. (3) Giraffe supports hierarchical data organization and in-memory storage for high throughput and low latency. We evaluate Giraffe on a high performance computing test-bed. The experimental results show that Giraffe gains much better write performance than ZooKeeper when server ensemble is large. Giraffe is nearly 300% faster than ZooKeeper on update operations when ensemble size is 50 servers. Experiments also show that Giraffe reacts and recovers more quickly than ZooKeeper against node failures.

Due to high flexibility and cost-effectiveness, cloud computing is increasingly being explored as an alternative to local clusters by academic and commercial users. Recent research already confirmed the feasibility of running tightly-coupled parallel applications with virtual clusters. However, such types of applications suffer from significant performance degradation, especially as the overcommitment is common in cloud. That is, the number of executable Virtual CPUs (VCPUs) is often larger than that of available Physical CPUs (PCPUs) in the system. The performance degradation mainly results from that the current Virtual Machine Monitors (VMMs) cannot co-schedule (or coordinate at the same time) the VCPUs that host parallel application threads/processes with synchronization requirements.

HPC community projects that future extreme scale systems will be much less stable than current Petascale systems, thus requiring sophisticated fault tolerance to guarantee the completion of large scale numerical computations. Execution failures may occur due to multiple factors with different scales, from transient uncorrectable memory errors localized in processes to massive system outages. Multi-level checkpoint/restart is a promising model that provides an elastic response to tolerate different types of failures. It stores checkpoints at different levels: e.g., local memory, remote memory, using a software RAID, local SSD, remote file system. In this paper, we respond to two open questions: 1) how to optimize the selection of checkpoint levels based on failure distributions observed in a system, 2) how to compute the optimal checkpoint intervals for each of these levels. The contribution is three-fold. (1) We build a mathematical model to fit the multi-level checkpoint/restart mechanism with large scale applications regarding various types of failures. (2) We theoretically optimize the entire execution performance for each parallel application by selecting the best checkpoint level combination and corresponding checkpoint intervals. (3) We characterize checkpoint overheads on different checkpoint levels in a real cluster environment, and evaluate our optimal solutions using both simulation with millions of cores and real environment with real-world MPI programs running on hundreds of cores. Experiments show that optimized selections of levels associated with optimal checkpoint intervals at each level outperforms other state-of-the-art solutions by 5-50 percent.

Future extreme-scale systems are expected to experience different types of failures affecting applications with different failure scales, from transient uncorrectable memory errors in processes to massive system outages. In this paper, we propose a multilevel checkpoint model by taking into account uncertain execution scales (different numbers of processes/cores). The contribution is threefold: (1) we provide an in-depth analysis on why it is difficult to derive the optimal checkpoint intervals for different checkpoint levels and optimize the number of cores simultaneously, (2) we devise a novel method that can quickly obtain an optimized solution -- the first successful attempt in multilevel checkpoint models with uncertain scales, and (3) we perform both large scale real experiments and extreme-scale numerical simulation to validate the effectiveness of our design. The experiments confirm that our optimized solution outperforms other state of-the-art solutions by 4.3 -- 88% on wall-clock length.

Compared to traditional distributed computing like grid system, it is non-trivial to optimize cloud task's execution performance due to its more constraints like user payment budget and divisible resource demand. In this paper, we analyze in-depth our proposed optimal algorithm minimizing task execution length with divisible resources and payment budget: 1) We derive the upper bound of cloud task length, by taking into account both workload prediction errors and hostload prediction errors. With such state-of-the-art bounds, the worst-case task execution performance is predictable, which can improve the quality of service in turn. 2) We design a dynamic version for the algorithm to adapt to the load dynamics over task execution progress, further improving the resource utilization. 3) We rigorously build a cloud prototype over a real cluster environment with 56 virtual machines, and evaluate our algorithm with different levels of resource contention. Cloud users in our cloud system are able to compose various tasks based on off-the-shelf web services. Experiments show that task execution lengths under our algorithm are always close to their theoretical optimal values, even in a competitive situation with limited available resources. We also observe a high level of fair treatment on the resource allocation among all tasks.

In modern cloud systems, how to optimize user service level based on virtual resources customized on demand is a critical issue. In this paper, we comprehensively analyze the payment bound under a cloud model with virtual machines (VMs), by taking into account that task's workload may be predicted with errors. The analysis is based on an optimized resource allocation algorithm with polynomial time complexity. We theoretically derive the upper bound of task payment based on a particular margin of workload prediction-error. We also extend the payment-minimization algorithm to adapt to the dynamic changes of host availability over time, and perform the evaluation by a real-cluster environment with 56 VMs deployed. Experiments confirm the correctness of our theoretical inference, and show that our payment-minimization solution can keep 95% of user payments below 1.15 times as large as the theoretical values of the ideal payment with hypothetically accurate information. The ratio for the rest user payments can be limited to about 1.5 at the worst case.

In cloud systems, it is non-trivial to optimize task's execution performance under user's affordable budget, especially with possible workload prediction errors. Based on an optimal algorithm that can minimize cloud task's execution length with predicted workload and budget, we theoretically derive the upper bound of the task execution length by taking into account the possible workload prediction errors. With such a state-of-the-art bound, the worst-case performance of a task execution with a certain workload prediction errors is predictable. On the other hand, we build a close-to-practice cloud prototype over a real cluster environment deployed with 56 virtual machines, and evaluate our solution with different resource contention degrees. Experiments show that task execution lengths under our solution with estimates of worst-case performance are close to their theoretical ideal values, in both non-competitive situation with adequate resources and the competitive situation with a certain limited available resources. We also observe a fair treatment on the resource allocation among all tasks.

In this paper, we characterize Google applications, based on a one-month Google trace with over 650k jobs running across over 12000 heterogeneous hosts from a Google data center. On one hand, we carefully compute the valuable statistics about task events and resource utilization for Google applications, based on various types of resources (such as CPU, memory) and execution types (e.g., whether they can run batch tasks or not). Resource utilization per application is observed with an extremely typical Pareto principle. On the other hand, we classify applications via a K-means clustering algorithm with optimized number of sets, based on task events and resource usage. The number of applications in the K-means clustering sets follows a Pareto-similar distribution. We believe our work is very interesting and valuable for the further investigation of Cloud environment.

With virtual machines (VM), we design a cloud system aiming to optimize the overall performance, in processing user requests made up of composite services. We address three contributions. (1) We optimize VM resource allocation with a minimized processing overhead subject to task's payment budget. (2) For maximizing the fairness of treatment in a competitive situation, we investigate the best-suited scheduling policy. (3) We devise a resource sharing scheme adjusted based on Proportional-Share model, further mitigating the resource contention. Experiments confirm two points: (1) mean task response time approaches the theoretically optimal value in non-competitive situation; (2) as system runs in short supply, each request could still be processed efficiently as compared to their ideal results. Combining Lightest Workload First (LWF) policy with Adjusted Proportional-Share Model (LWF+APSM) exhibits the best performance. It outperforms others in a competitive situation, by 38% w.r.t. worst-case response time and by 12% w.r.t. fairness of treatment.

In this paper, we aim at optimizing fault-tolerance techniques based on a checkpointing/restart mechanism, in the context of cloud computing. Our contribution is three-fold. (1) We derive a fresh formula to compute the optimal number of checkpoints for cloud jobs with varied distributions of failure events. Our analysis is not only generic with no assumption on failure probability distribution, but also attractively simple to apply in practice. (2) We design an adaptive algorithm to optimize the impact of checkpointing regarding various costs like checkpointing/restart overhead. (3) We evaluate our optimized solution in a real cluster environment with hundreds of virtual machines and Berkeley Lab Checkpoint/Restart tool. Task failure events are emulated via a production trace produced on a large-scale Google data center. Experiments confirm that our solution is fairly suitable for Google systems. Our optimized formula outperforms Young's formula by 3-10 percent, reducing wall-clock lengths by 50-100 seconds per job on average.

By leveraging virtual machine (VM) technology which provides performance and fault isolation, cloud resources can be provisioned on demand in a fine grained, multiplexed manner rather than in monolithic pieces. By integrating volunteer computing into cloud architectures, we envision a gigantic self-organizing cloud (SOC) being formed to reap the huge potential of untapped commodity computing power over the Internet. Toward this new architecture where each participant may autonomously act as both resource consumer and provider, we propose a fully distributed, VM-multiplexing resource allocation scheme to manage decentralized resources. Our approach not only achieves maximized resource utilization using the proportional share model (PSM), but also delivers provably and adaptively optimal execution efficiency. We also design a novel multiattribute range query protocol for locating qualified nodes. Contrary to existing solutions which often generate bulky messages per request, our protocol produces only one lightweight query message per task on the Content Addressable Network (CAN). It works effectively to find for each task its qualified resources under a randomized policy that mitigates the contention among requesters. We show the SOC with our optimized algorithms can make an improvement by 15-60 percent in system throughput than a P2P Grid model. Our solution also exhibits fairly high adaptability in a dynamic node-churning environment.

With virtual machine (VM) technology being increasingly mature, compute resources in cloud systems can be partitioned in fine granularity and allocated on demand. We make three contributions in this paper: 1) We formulate a deadline-driven resource allocation problem based on the cloud environment facilitated with VM resource isolation technology, and also propose a novel solution with polynomial time, which could minimize users' payment in terms of their expected deadlines. 2) By analyzing the upper bound of task execution length based on the possibly inaccurate workload prediction, we further propose an error-tolerant method to guarantee task's completion within its deadline. 3) We validate its effectiveness over a real VM-facilitated cluster environment under different levels of competition. In our experiment, by tuning algorithmic input deadline based on our derived bound, task execution length can always be limited within its deadline in the sufficient-supply situation; the mean execution length still keeps 70 percent as high as user-specified deadline under the severe competition. Under the original-deadline-based solution, about 52.5 percent of tasks are completed within 0.95-1.0 as high as their deadlines, which still conforms to the deadline-guaranteed requirement. Only 20 percent of tasks violate deadlines, yet most (17.5 percent) are still finished within 1.05 times of deadlines.

A new era of Cloud Computing has emerged, but the characteristics of Cloud load in data centers is not perfectly clear. Yet this characterization is critical for the design of novel Cloud job and resource management systems. In this paper, we comprehensively characterize the job/task load and host load in a real-world production data center at Google Inc. We use a detailed trace of over 25 million tasks across over 12,500 hosts. We study the differences between a Google data center and other Grid/HPC systems, from the perspective of both work load (w.r.t. jobs and tasks) and host load (w.r.t. machines). In particular, we study the job length, job submission frequency, and the resource utilization of jobs in the different systems, and also investigate valuable statistics of machine's maximum load, queue state and relative usage levels, with different job priorities and resource attributes. We find that the Google data center exhibits finer resource allocation with respect to CPU and memory than that of Grid/HPC systems. Google jobs are always submitted with much higher frequency and they are much shorter than Grid jobs. As such, Google host load exhibits higher variance and noise.

Prediction of host load in Cloud systems is critical for achieving service-level agreements. However, accurate prediction of host load in Clouds is extremely challenging because it fluctuates drastically at small timescales. We design a prediction method based on Bayes model to predict the mean load over a long-term time interval, as well as the mean load in consecutive future time intervals. We identify novel predictive features of host load that capture the expectation, predictability, trends and patterns of host load. We also determine the most effective combinations of these features for prediction. We evaluate our method using a detailed one-month trace of a Google data center with thousands of machines. Experiments show that the Bayes method achieves high accuracy with a mean squared error of 0.0014. Moreover, the Bayes method improves the load prediction accuracy by 5.6 -- 50% compared to other state-of-the-art methods based on moving averages, auto-regression, and/or noise filters.

With virtual machine (VM) technology being increasingly mature, computing resources in modern Cloud systems can be partitioned in fine granularity and allocated on demand with "pay-as-you-go" model. In this work, we study the resource query and allocation problems in a Self-Organizing Cloud (SOC), where host machines are connected by a peer-to-peer (P2P) overlay network on the Internet. To run a user task in SOC, the requester needs to perform a multi-dimensional range search over the P2P network for locating host machines that satisfy its minimal demand on each type of resources. The multi-dimensional range search problem is known to be challenging as contentions along multiple dimensions could happen in the presence of the uncoordinated analogous queries. Moreover, low resource matching rate may happen while restricting query delay and network traffic. We design a novel resource discovery protocol, namely Proactive Index Diffusion CAN (PID-CAN), which can proactively diffuse resource indexes over the nodes and randomly route query messages among them. Such a protocol is especially suitable for the range query that needs to maximize its best-fit resource shares under possible competition along multiple resource dimensions. Via simulation, we show that PID-CAN could keep stable and optimized searching performance with low query delay and traffic overhead, for various test cases under different distributions of query ranges and competition degrees. It also performs satisfactorily in dynamic node-churning situation.

A Virtual Private Cloud (VPC) is a secure collection of computing, storage and network resources spanning multiple sites over Wide Area Network (WAN). With VPC, computation and services are no longer restricted to a fixed site but can be relocated dynamically across geographical sites to improve manageability, performance and fault tolerance. We propose WAVNet, a layer 2 virtual private network (VPN) which supports virtual machine live migration over WAN to realize mobility of execution environment across multiple security domains. WAVNet adopts a UDP hole punching technique to achieve direct network connection between two Internet hosts without special router configuration. We evaluate our design in an emulated WAN with 64 hosts and also in a real WAN environment with 10 machines located at seven different sites across the Asia-Pacific region. The experimental results show that WAVNet not only achieves close-to-native host-to-host network bandwidth and latency, but also guarantees more effective VM live migration than existing solutions.

This paper presents a fully decentralized just-in-time workflow scheduling method in a P2P Grid system. The proposed solution allows each peer node to autonomously dispatch inter-dependent tasks of workflows to run on geographically distributed computers. To reduce the workflow completion time and enhance the overall execution efficiency, not only does each node perform as a scheduler to distribute its tasks to execution nodes (or resource nodes), but the resource nodes will also set the execution priorities for the received tasks. By taking into account the unpredictability of tasks' finish time, we devise an efficient task scheduling heuristic, namely dynamic shortest makespan first (DSMF), which could be applied at both scheduling phases for determining the priority of the workflow tasks. We compare the performance of the proposed algorithm against seven other heuristics by simulation. Our algorithm achieves 20%~60% reduction on the average completion time and 37.5%~90% improvement on the average workflow execution efficiency over other decentralized algorithms.

With the development of semantic Web, search efficiency is becoming a challenging issue. To address this problem, we design an approach which mainly has two features. First, we explore potential semantic relationship between different objects and make full use of them to build a semantic buffer on server end, enhancing search speed. Second, we put another relatively small semantic buffer on each client so as to adapt to each individual user's interests, further improving the whole search efficiency and reducing server's load. Through testing on a practical platform, we testified that this semantic double-buffer based search approach can not only effectively reduce user's request response time, but considerably release server's load, bringing a high scalability.

GlobalWatch is a distributed platform to monitor various resources of grid platforms so as to improve the flexibility and usability of grid systems. In order to enhance the flexibility, we make improvements from three aspects. 1) We take advantage of both centralized and decentralized methods in the architecture and adopt a loosely coupled architecture to get monitored data; 2) We integrate GlobalWatch with VO (Virtual Organization) concept so as to make it compatible with grid circumstances. 3) We design a XML format to make GlobalWatch flexible for users to submit and receive information. In order to enhance the usability, we not only integrate various functions into GlobalWatch client application, but also make the visual effect better than some other monitoring platforms. At last, we conclude from the experimental result that monitored nodes in GlobalWatch are indeed loosely coupled and the transmission of map data is the main bottleneck in server end