5,960 research outputs found
Performance Analysis and Optimization of Sparse Matrix-Vector Multiplication on Modern Multi- and Many-Core Processors
This paper presents a low-overhead optimizer for the ubiquitous sparse
matrix-vector multiplication (SpMV) kernel. Architectural diversity among
different processors together with structural diversity among different sparse
matrices lead to bottleneck diversity. This justifies an SpMV optimizer that is
both matrix- and architecture-adaptive through runtime specialization. To this
direction, we present an approach that first identifies the performance
bottlenecks of SpMV for a given sparse matrix on the target platform either
through profiling or by matrix property inspection, and then selects suitable
optimizations to tackle those bottlenecks. Our optimization pool is based on
the widely used Compressed Sparse Row (CSR) sparse matrix storage format and
has low preprocessing overheads, making our overall approach practical even in
cases where fast decision making and optimization setup is required. We
evaluate our optimizer on three x86-based computing platforms and demonstrate
that it is able to distinguish and appropriately optimize SpMV for the majority
of matrices in a representative test suite, leading to significant speedups
over the CSR and Inspector-Executor CSR SpMV kernels available in the latest
release of the Intel MKL library.Comment: 10 pages, 7 figures, ICPP 201
Modeling the Resource Requirements of Convolutional Neural Networks on Mobile Devices
Convolutional Neural Networks (CNNs) have revolutionized the research in
computer vision, due to their ability to capture complex patterns, resulting in
high inference accuracies. However, the increasingly complex nature of these
neural networks means that they are particularly suited for server computers
with powerful GPUs. We envision that deep learning applications will be
eventually and widely deployed on mobile devices, e.g., smartphones,
self-driving cars, and drones. Therefore, in this paper, we aim to understand
the resource requirements (time, memory) of CNNs on mobile devices. First, by
deploying several popular CNNs on mobile CPUs and GPUs, we measure and analyze
the performance and resource usage for every layer of the CNNs. Our findings
point out the potential ways of optimizing the performance on mobile devices.
Second, we model the resource requirements of the different CNN computations.
Finally, based on the measurement, pro ling, and modeling, we build and
evaluate our modeling tool, Augur, which takes a CNN configuration (descriptor)
as the input and estimates the compute time and resource usage of the CNN, to
give insights about whether and how e ciently a CNN can be run on a given
mobile platform. In doing so Augur tackles several challenges: (i) how to
overcome pro ling and measurement overhead; (ii) how to capture the variance in
different mobile platforms with different processors, memory, and cache sizes;
and (iii) how to account for the variance in the number, type and size of
layers of the different CNN configurations
On the Bayes-optimality of F-measure maximizers
The F-measure, which has originally been introduced in information retrieval,
is nowadays routinely used as a performance metric for problems such as binary
classification, multi-label classification, and structured output prediction.
Optimizing this measure is a statistically and computationally challenging
problem, since no closed-form solution exists. Adopting a decision-theoretic
perspective, this article provides a formal and experimental analysis of
different approaches for maximizing the F-measure. We start with a Bayes-risk
analysis of related loss functions, such as Hamming loss and subset zero-one
loss, showing that optimizing such losses as a surrogate of the F-measure leads
to a high worst-case regret. Subsequently, we perform a similar type of
analysis for F-measure maximizing algorithms, showing that such algorithms are
approximate, while relying on additional assumptions regarding the statistical
distribution of the binary response variables. Furthermore, we present a new
algorithm which is not only computationally efficient but also Bayes-optimal,
regardless of the underlying distribution. To this end, the algorithm requires
only a quadratic (with respect to the number of binary responses) number of
parameters of the joint distribution. We illustrate the practical performance
of all analyzed methods by means of experiments with multi-label classification
problems
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