NoSQL data-stores are commonly used to provide flexibility and availability for big data handling. However, there is a lack of comprehensive studies about which NoSQL data-store performs the best from the two scalability aspects, (scale-up, and scale-out), in a distributed and parallel processing environment. This paper compares the popular NoSQL data-stores (Cassandra, HBase, and MongoDB) and analyzes the resulting performance. Our experiments measure throughput, latency, and run-time of the evaluated data-stores on a big data set that consist of standard benchmarking workloads. Our results provide that the performance of each NoSQL data-store varies according to two main factors, (a) the type of executed operation, (read, scan, update, write, and insert), and (b) the level of distribution.

In this paper, we consider the problem of event prediction with multi-variate time series data consisting of heterogeneous (continuous and categorical) variables. The complex dependencies between the variables combined with asynchronicity and sparsity of the data makes the event prediction problem particularly challenging. Most state-of-art approaches address this either by designing hand-engineered features or breaking up the problem over homogeneous variates. In this work, we formulate the (rare) event prediction task as a classification problem with a novel asymmetric loss function and propose an end-to-end deep learning algorithm over symbolic representations of time-series. Symbolic representations are fed into an embedding layer and a Long Short Term Memory Neural Network (LSTM) layer which are trained to learn discriminative features. We also propose a simple sequence chopping technique to speed-up the training of LSTM for long temporal sequences. Experiments on real-world industrial datasets demonstrate the effectiveness of the proposed approach.

Most machine learning algorithms involve solving a convex optimization problem. Traditional in-memory convex optimization solvers do not scale well with the increase in data. This paper identifies a generic convex problem for most machine learning algorithms and solves it using the Alternating Direction Method of Multipliers (ADMM). Finally such an ADMM problem transforms to an iterative system of linear equations, which can be easily solved at scale in a distributed fashion. We implement this framework in Apache Spark and compare it with the widely used Machine Learning LIBrary (MLLIB) in Apache Spark 1.3.

In this paper, we focus on the task of learning influential parameters under unsteady and dynamic environments. Such unsteady and dynamic environments often occur in the ramp-up phase of manufacturing. We propose a novel regularization-based framework, called Distributed Dynamic Elastic Nets (DDEN), for this problem and formulate it as a convex optimization objective. Our approach solves the optimization problem using a distributed framework. Consequently it is highly scalable and can easily be applied to very large datasets. We implement a L-BFGS based solver in the Apache Spark framework. For validating our algorithm, we consider the issue of scrap reduction at an assembly line during the ramp-up phase of a manufacturing plant. By considering the logistic regression as a sample model, we evaluate the performance of our approach although extensions of the proposed regularizer to other classification and regression techniques is straightforward. Through experiments on data collected at a functioning manufacturing plant, we show that the proposed method not only reduces model variance but also helps preserve the relative importance of features in dynamic conditions compared to standard approaches. The experiments further show that the classification performance of DDEN if often better than logistic regression with standard elastic nets for datasets from dynamic and unsteady environments. We are collaborating with manufacturing units to use this process for improving production yields during the ramp-up phase. This work serves as a demonstration of how data mining can be used to solve problem in manufacturing.

Sparse coding, an unsupervised feature learning technique, is often used as a basic building block to construct deep networks. Convolutional sparse coding is proposed in the literature to overcome the scalability issues of sparse coding techniques to large images. In this paper we propose an efficient algorithm, based on the fast iterative shrinkage thresholding algorithm (FISTA), for learning sparse convolutional features. Through numerical experiments, we show that the proposed convolutional extension of FISTA can not only lead to faster convergence compared to existing methods but can also easily generalize to other cost functions.

We consider the problem of joint enhancement of multichannel images with pixel based constraints on the multichannel data. Previous work by Cetin and Karl introduced nonquadratic regularization methods for SAR image enhancement using sparsity enforcing penalty terms. We formulate an optimization problem that jointly enhances complex-valued multichannel images while preserving the cross-channel information, which we include as constraints tying the multichannel images together. We pose this problem as a joint optimization problem with constraints. We first reformulate it as an equivalent (unconstrained) dual problem and develop a numerically-efficient method for solving it. We develop the Dual Descent method, which has low complexity, for solving the joint optimization problem. The algorithm is applied to both an interferometric synthetic aperture radar (IFSAR) problem, in which the relative phase between two complex-valued images indicate height, and to a synthetic multimodal medical image example.