The parallelization of Smith-Waterman (SW) sequence comparison tools for long DNA sequences has been a big challenge over the years, requesting the use of several devices and sophisticated optimizations. Pruning is one of these optimizations, which can reduce considerably the amount of computation. This article proposes MultiBP, a sequence comparison solution in multiple GPUs with block pruning. Two MultiBP strategies are proposed. In static score-sharing, workload is statically distributed to the GPUs, and the best score is sent to neighbor GPUs to simulate a global view. In the dynamic strategy, execution is divided into cycles and workload is dynamically assigned, according to the GPUs processing rate. MultiBP was integrated to MASA-CUDAlign and tested in homogeneous and heterogeneous platforms, with different NVidia GPU architectures. The best results in our homogeneous and heterogeneous platforms were mostly obtained by the static and dynamic approaches, respectively. We also show that our decision module is able to select the best strategy in most cases. Finally, the comparison of the human and chimpanzee chromosomes 1 in a cluster with 512 V100 NVidia GPUs took 11 minutes and obtained the impressive rate of 82,822 GCUPS (Billions of Cells Updated per Second) which is, to our knowledge, the best performance for SW tools in GPUs.

Sequence comparison is a task performed in several Bioinformatics applications daily all over the world. Algorithms that retrieve the optimal result have quadratic time complexity, requiring a huge amount of computing power when the sequences compared are long. In order to reduce the execution time, many parallel solutions have been proposed in the literature. Nevertheless, depending on the sizes of the sequences, even those parallel solutions take hours or days to complete. Pruning techniques can significantly improve the performance of the parallel solutions and a few approaches have been proposed to provide pruning capabilities for sequence comparison applications. This paper proposes and evaluates a variant of the block pruning approach that runs in multiple GPUs, in homogeneous or heterogeneous environments. Experimental results obtained with DNA sequences in two testbeds show that significant performance gains are obtained with pruning, compared to its non-pruning counterpart, achieving the impressive performance of 694.8 GCUPS (Billions of Cells Updated per Second) for four GPUs.

Summary Biological sequence comparison is often used as an auxiliary task in the analysis of genetic material. Pairwise comparison algorithms like Smith‐Waterman evaluate two strings representing sequences of proteins, DNA or RNA to obtain optimal alignment between them. Many applications have been proposed to address the sequence comparison problem, prioritizing the use of graphics cards and proprietary languages such as CUDA. In this paper, we propose and evaluate MASA‐OpenCL, an OpenCL solution for comparing long DNA sequences that is based on the MASA sequence alignment framework, with pruning capability proportional to the similarity of the sequences compared. The results of MASA‐OpenCL were compared to its CUDA counterpart (MASA‐CUDAlign) and, in most cases, MASA‐OpenCL achieved better performance. In order to better understand the behavior of MASA‐OpenCL, we performed a statistical analysis considering 11 comparisons of sequences with high, medium and low similarity in 4 GPUs. As a result, we obtained a multiple linear regression model that considers (a) the sizes of the sequences, (b) the similarity between them, (c) the computational power of the GPU, and (d) the GPU memory bandwidth. We used this model to predict the performance in two other GPUs, with low error rates.

Biological sequence comparison is a very common task in Bioinformatics applications. Many parallel solutions have been proposed for this problem, using different HPC platforms, programmed usually with platform-specific languages and frameworks. With this approach, it is difficult to port solutions among different platforms such as CPUs and GPUs, for instance. To tackle this problem, this paper proposes and evaluates an OpenCL parallel solution for Biological Sequence Comparison, which was integrated to the CUDAlign Megabase Sequence Comparison tool. The evaluation of our solution shows we were able to obtain a program for CPUs and GPUs (NVidia and AMD) with basically the same OpenCL code. In addition, in the comparison with SW# and CUDAlign optimized CUDA codes, we show that the performance of our OpenCL version has comparable and, many times, superior performance.