1,720,958 research outputs found
Design patterns for sparse-matrix computations on hybrid CPU/GPU platforms
Full text linkWe apply object-oriented software design patterns to develop code for scientific software involving sparse matrices. Design patterns arise when multiple independent developments produce similar designs which converge onto a generic solution. We demonstrate how to use design patterns to implement an interface for sparse matrix computations on NVIDIA GPUs starting from PSBLAS, an existing sparse matrix library, and from existing sets of GPU kernels for sparse matrices. We also compare the throughput of the PSBLAS sparse matrix–vector multiplication on two platforms exploiting the GPU with that obtained by a CPU-only PSBLAS implementation. Our experiments exhibit encouraging results regarding the comparison between CPU and GPU executions in double precision, obtaining a speedup of up to 35.35 on NVIDIA GTX 285 with respect to AMD Athlon 7750, and up to 10.15 on NVIDIA Tesla C2050 with respect to Intel Xeon X5650
Design patterns for scientific computations on sparse matrices
No full textWe discuss object-oriented software design patterns in the context of scientific computations on sparse matrices. Design patterns arise when multiple independent development efforts produce very similar designs, yielding an evolutionary convergence onto a good solution: a flexible, maintainable, high-performance design. We demonstrate how to engender these traits by implementing an interface for sparse matrix computations on NVIDIA GPUs starting from an existing sparse matrix library. We also present initial performance results
Hybrid coarrays: A PGAS feature for many-core architectures
No full textAccelerators such as NVIDIA GPUs and Intel MICs are currently provided as co-processor devices, usable only through a CPU host. For Intel MICs it is planned that this constraint will be lifted in the near future: CPU and accelerator(s) will then form a single, many-core, processor capable of peak performance of several Teraflops with high energy efficiency. In order to exploit the available computational power, the user will be compelled to write a code more “hardware-aware”, in contrast to the common philosophy of hiding hardware details as much as possible. The simple two-sided communication approach often used in message-passing applications introduces synchronization costs that may limit the performance on the next generation machines. PGAS languages, like coarray Fortran and UPC, propose a one-sided approach where a process accesses directly the remote memory of another process without interrupting its execution. In this paper, we propose a CUDA-aware coarray implementation, capable of merging the expressive syntax of coarrays with the computational power of GPUs. We propose a new keyword for the Fortran language, which allows the user to map with a high-level syntax some hardware features of the many-core machines. Our hybrid coarray implementation is based on OpenCoarrays, the coarray transport layer currently adopted by the GNU Fortran compiler
OpenCoarrays: open-source transport layers supporting coarray Fortran compilers
No full textCoarray Fortran is a set of features of the Fortran 2008 standard that make Fortran a PGAS parallel programming language. Two commercial compilers currently support coarrays: Cray and Intel. Here we present two coarray transport layers provided by the new OpenCoarrays project: one library based on MPI and the other on GASNet. We link the GNU Fortran (GFortran) compiler to either of the two OpenCoarrays implementations and present performance comparisons between executables produced by GFortran and the Cray and Intel compilers. The comparison includes synthetic benchmarks, application prototypes, and an application kernel. In our tests, Intel outperforms GFortran only on intra-node small transfers (in particular, scalars). GFortran outperforms Intel on intra-node array transfers and in all settings that require inter-node transfers. The Cray comparisons are mixed, with either GFortran or Cray being faster depending on the chosen hardware platform, network, and transport layer
Coarrays in GNU Fortran
No full textCoarray Fortran is a set of features of the Fortran 2008 standard which makes Fortran a PGAS language. Currently, the coarray support is provided mainly by commercial compilers like Cray and Intel. In this work we present two coarray implementations on the GNU Fortran compiler. We present a performance comparison between our coarray implementations and those provided by Cray and Intel. Such comparison includes synthetic benchmarks and real, commonly used, scientific applications
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
