3,588 research outputs found
A compiler extension for parallelizing arrays automatically on the cell heterogeneous processor
This paper describes the approaches taken to extend an array
programming language compiler using a Virtual SIMD Machine (VSM)
model for parallelizing array operations on Cell Broadband Engine heterogeneous
machine. This development is part of ongoing work at the
University of Glasgow for developing array compilers that are beneficial
for applications in many areas such as graphics, multimedia, image processing
and scientific computation. Our extended compiler, which is built
upon the VSM interface, eases the parallelization processes by allowing
automatic parallelisation without the need for any annotations or process
directives. The preliminary results demonstrate significant improvement
especially on data-intensive applications
pocl: A Performance-Portable OpenCL Implementation
OpenCL is a standard for parallel programming of heterogeneous systems. The
benefits of a common programming standard are clear; multiple vendors can
provide support for application descriptions written according to the standard,
thus reducing the program porting effort. While the standard brings the obvious
benefits of platform portability, the performance portability aspects are
largely left to the programmer. The situation is made worse due to multiple
proprietary vendor implementations with different characteristics, and, thus,
required optimization strategies.
In this paper, we propose an OpenCL implementation that is both portable and
performance portable. At its core is a kernel compiler that can be used to
exploit the data parallelism of OpenCL programs on multiple platforms with
different parallel hardware styles. The kernel compiler is modularized to
perform target-independent parallel region formation separately from the
target-specific parallel mapping of the regions to enable support for various
styles of fine-grained parallel resources such as subword SIMD extensions, SIMD
datapaths and static multi-issue. Unlike previous similar techniques that work
on the source level, the parallel region formation retains the information of
the data parallelism using the LLVM IR and its metadata infrastructure. This
data can be exploited by the later generic compiler passes for efficient
parallelization.
The proposed open source implementation of OpenCL is also platform portable,
enabling OpenCL on a wide range of architectures, both already commercialized
and on those that are still under research. The paper describes how the
portability of the implementation is achieved. Our results show that most of
the benchmarked applications when compiled using pocl were faster or close to
as fast as the best proprietary OpenCL implementation for the platform at hand.Comment: This article was published in 2015; it is now openly accessible via
arxi
A Survey on Compiler Autotuning using Machine Learning
Since the mid-1990s, researchers have been trying to use machine-learning
based approaches to solve a number of different compiler optimization problems.
These techniques primarily enhance the quality of the obtained results and,
more importantly, make it feasible to tackle two main compiler optimization
problems: optimization selection (choosing which optimizations to apply) and
phase-ordering (choosing the order of applying optimizations). The compiler
optimization space continues to grow due to the advancement of applications,
increasing number of compiler optimizations, and new target architectures.
Generic optimization passes in compilers cannot fully leverage newly introduced
optimizations and, therefore, cannot keep up with the pace of increasing
options. This survey summarizes and classifies the recent advances in using
machine learning for the compiler optimization field, particularly on the two
major problems of (1) selecting the best optimizations and (2) the
phase-ordering of optimizations. The survey highlights the approaches taken so
far, the obtained results, the fine-grain classification among different
approaches and finally, the influential papers of the field.Comment: version 5.0 (updated on September 2018)- Preprint Version For our
Accepted Journal @ ACM CSUR 2018 (42 pages) - This survey will be updated
quarterly here (Send me your new published papers to be added in the
subsequent version) History: Received November 2016; Revised August 2017;
Revised February 2018; Accepted March 2018
Design and optimization of a portable LQCD Monte Carlo code using OpenACC
The present panorama of HPC architectures is extremely heterogeneous, ranging
from traditional multi-core CPU processors, supporting a wide class of
applications but delivering moderate computing performance, to many-core GPUs,
exploiting aggressive data-parallelism and delivering higher performances for
streaming computing applications. In this scenario, code portability (and
performance portability) become necessary for easy maintainability of
applications; this is very relevant in scientific computing where code changes
are very frequent, making it tedious and prone to error to keep different code
versions aligned. In this work we present the design and optimization of a
state-of-the-art production-level LQCD Monte Carlo application, using the
directive-based OpenACC programming model. OpenACC abstracts parallel
programming to a descriptive level, relieving programmers from specifying how
codes should be mapped onto the target architecture. We describe the
implementation of a code fully written in OpenACC, and show that we are able to
target several different architectures, including state-of-the-art traditional
CPUs and GPUs, with the same code. We also measure performance, evaluating the
computing efficiency of our OpenACC code on several architectures, comparing
with GPU-specific implementations and showing that a good level of
performance-portability can be reached.Comment: 26 pages, 2 png figures, preprint of an article submitted for
consideration in International Journal of Modern Physics
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