Numerical Initial Value Problems in Ordinary Differential Equations

Increasing focus on multimedia applications has prompted the addition of multimedia extensions to most existing general purpose microprocessors. This added functionality comes primarily with the addition of short SIMD instructions. Unfortunately, access to these instructions is limited to in-line assembly and library calls. Generally, it has been assumed that vector compilers provide the most promising means of exploiting multimedia instructions. Although vectorization technology is well understood, it is inherently complex and fragile. In addition, it is incapable of locating SIMD-style parallelism within a basic block.In this paper we introduce the concept of Superword Level Parallelism (SLP) ,a novel way of viewing parallelism in multimedia and scientific applications. We believe SLPP is fundamentally different from the loop level parallelism exploited by traditional vector processing, and therefore demands a new method of extracting it. We have developed a simple and robust compiler for detecting SLPP that targets basic blocks rather than loop nests. As with techniques designed to extract ILP, ours is able to exploit parallelism both across loop iterations and within basic blocks. The result is an algorithm that provides excellent performance in several application domains. In our experiments, dynamic instruction counts were reduced by 46%. Speedups ranged from 1.24 to 6.70.

/pdf/exploiting-superword-level-parallelism-with-multimedia-1ihagkottn.pdf

Exploiting superword level parallelism with multimedia instruction sets

Diagnostic messages generated by compilers and interpreters such as syntax error messages have been researched for over half of a century. Unfortunately, these messages which include error, warning, and run-time messages, present substantial difficulty and could be more effective, particularly for novices. Recent years have seen an increased number of papers in the area including studies on the effectiveness of these messages, improving or enhancing them, and their usefulness as a part of programming process data that can be used to predict student performance, track student progress, and tailor learning plans. Despite this increased interest, the long history of literature is quite scattered and has not been brought together in any digestible form.In order to help the computing education community (and related communities) to further advance work on programming error messages, we present a comprehensive, historical and state-of-the-art report on research in the area. In addition, we synthesise and present the existing evidence for these messages including the difficulties they present and their effectiveness. We finally present a set of guidelines, curated from the literature, classified on the type of evidence supporting each one (historical, anecdotal, and empirical). This work can serve as a starting point for those who wish to conduct research on compiler error messages, runtime errors, and warnings. We also make the bibtex file of our 300+ reference corpus publicly available. Collectively this report and the bibliography will be useful to those who wish to design better messages or those that aim to measure their effectiveness, more effectively.

Compiler Error Messages Considered Unhelpful: The Landscape of Text-Based Programming Error Message Research

In recent years, microprocessor manufacturers have shifted their focus from single-core to multi-core processors. To avoid burdening programmers with the responsibility of parallelizing their applications, some researchers have advocated automatic thread extraction. A recently proposed technique, Decoupled software pipelining (DSWP), has demonstrated promise by partitioning loops into long-running, fine-grained threads organized into a pipeline. Using a pipeline organization and execution decoupled by inter-core communication queues, DSWP offers increased execution efficiency that is largely independent of inter-core communication latency. This paper proposes adding speculation to DSWP and evaluates an automatic approach for its implementation. By speculating past infrequent dependences, the benefit of DSWP is increased by making it applicable to more loops, facilitating better balanced threads, and enabling parallelized loops to be run on more cores. Unlike prior speculative threading proposals, speculative DSWP focuses on breaking dependence recurrences. By speculatively breaking these recurrences, instructions that were formerly restricted to a single thread to ensure decoupling are now free to span multiple threads. Using an initial automatic compiler implementation and a validated processor model, this paper demonstrates significant gains using speculation for 4-core chip multiprocessor models running a variety of codes.

/pdf/speculative-decoupled-software-pipelining-4b1u0zwvnz.pdf

Speculative Decoupled Software Pipelining

Publisher Summary This chapter discusses MARMOT, a tool to check during runtime if message passing interface (MPI) application conforms to the MPI standard— that is, if resources like communicators, datatypes etc., and other parameters are handled correctly. Another problem with parallel programs is the occurrence of race conditions or deadlocks. Examples are the introduction of irreproducibility, deadlocks, and incorrect management of resources like communicators, groups, datatypes, and operators. The benchmark results show that the use of MARMOT introduces a certain overhead, especially when the execution is serialized. As the development of MARMOT is still ongoing, the main emphasis has so far been on implementing its functionality and not on optimizing its performance. However, the benchmarks results show that for applications with a reasonable communication to computation ratio, the overhead of using MARMOT is below 20%–50% on up to 16 processors. The idea of MARMOT is to verify the standard conformance of an MPI program automatically during runtime and help to debug the program in case of problems.

/pdf/marmot-an-mpi-analysis-and-checking-tool-51hhhts952.pdf

MARMOT: An MPI analysis and checking tool

SUMMARY The Message-Passing Interface (MPI) is commonly used to write parallel programs for distributed memory parallel computers. MPI-CHECK is a tool developed to aid in the debugging of MPI programs that are written in free or fixed format Fortran 90 and Fortran 77. This paper presents the methods used in MPI-CHECK 2.0 to detect many situationswhereactual andpotential deadlocksoccur whenusingblocking and non-blocking point-to-point routines as well as when using collective routines. Copyright  2002 John Wiley & Sons, Ltd.

Deadlock detection in MPI programs

This paper evaluates the ability of a variety of commercial and non-commercial software products to detect serial run-time errors in C and C++ programs, to issue meaningful messages, and to give the line in the source code where the error occurred. The commercial products Insure++ and Purify performed the best of all the software products we evaluated. Error messages were usually better and clearer when using Insure++ than when using Purify. Our evaluation shows that the overall capability of detecting run-time errors of non-commercial products is significantly lower than the quality of both Purify and Insure++. Of all non-commercial products evaluated, Mpatrol provided the best overall capability to detect run-time errors in C and C++ programs. Copyright © 2006 John Wiley & Sons, Ltd.

A survey of systems for detecting serial run-time errors: Research Articles

A survey of systems for detecting serial run‐time errors

Unified Parallel C (UPC) is a language used to write parallel programs for distributed memory parallel computers. UPC-CHECK ( http://hpcgroup.public.iastate.edu/UPC-CHECK/ ) is a scalable tool developed to automatically detect argument errors in UPC functions and deadlocks in UPC programs at run-time and issue high quality error messages to help programmers quickly fix those errors. The run-time complexity of all detection techniques used are optimal, i.e. O(1) except for deadlocks involving locks where it is theoretically known to be linear in the number of threads. The tool is easy to use, and involves merely replacing the compiler command with upc-check. Error messages issued by UPC-CHECK were evaluated using the UPC RTED test suite for argument errors in UPC functions and deadlocks. Results of these tests show that the error messages issued by UPC-CHECK for these tests are excellent.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=3456&context=etd

UPC-CHECK: a scalable tool for detecting run-time errors in Unified Parallel C

The ability of system software to detect run-time errors and issue messages that help programmers quickly fix these errors is an important productivity criterion for developing and maintaining application programs. To evaluate this capability for Unified Parallel C (UPC), over two thousand run-time error tests and a run-time error detection (RTED) evaluation tool have been developed. For each error message issued, the RTED evaluation tool assigns a score from 0 to 5 based on the usefulness of the information in the message to help a programmer quickly fix the error. The RTED evaluation tool calculates averages over each error category and then prints the results. All tests and the RTED evaluation tool are freely available at the RTED web site http://rted.public.iastate.edu/UPC. The Cray, Berkeley, HP and GNU UPC compilers have been evaluated and results posted on this same web site.

Evaluating error detection capabilities of UPC run-time systems

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