47,419 research outputs found
A Comparative Study of Some Pseudorandom Number Generators
We present results of an extensive test program of a group of pseudorandom
number generators which are commonly used in the applications of physics, in
particular in Monte Carlo simulations. The generators include public domain
programs, manufacturer installed routines and a random number sequence produced
from physical noise. We start by traditional statistical tests, followed by
detailed bit level and visual tests. The computational speed of various
algorithms is also scrutinized. Our results allow direct comparisons between
the properties of different generators, as well as an assessment of the
efficiency of the various test methods. This information provides the best
available criterion to choose the best possible generator for a given problem.
However, in light of recent problems reported with some of these generators, we
also discuss the importance of developing more refined physical tests to find
possible correlations not revealed by the present test methods.Comment: University of Helsinki preprint HU-TFT-93-22 (minor changes in Tables
2 and 7, and in the text, correspondingly
Lemon: an MPI parallel I/O library for data encapsulation using LIME
We introduce Lemon, an MPI parallel I/O library that is intended to allow for
efficient parallel I/O of both binary and metadata on massively parallel
architectures. Motivated by the demands of the Lattice Quantum Chromodynamics
community, the data is stored in the SciDAC Lattice QCD Interchange Message
Encapsulation format. This format allows for storing large blocks of binary
data and corresponding metadata in the same file. Even if designed for LQCD
needs, this format might be useful for any application with this type of data
profile. The design, implementation and application of Lemon are described. We
conclude with presenting the excellent scaling properties of Lemon on state of
the art high performance computers
From Physics Model to Results: An Optimizing Framework for Cross-Architecture Code Generation
Starting from a high-level problem description in terms of partial
differential equations using abstract tensor notation, the Chemora framework
discretizes, optimizes, and generates complete high performance codes for a
wide range of compute architectures. Chemora extends the capabilities of
Cactus, facilitating the usage of large-scale CPU/GPU systems in an efficient
manner for complex applications, without low-level code tuning. Chemora
achieves parallelism through MPI and multi-threading, combining OpenMP and
CUDA. Optimizations include high-level code transformations, efficient loop
traversal strategies, dynamically selected data and instruction cache usage
strategies, and JIT compilation of GPU code tailored to the problem
characteristics. The discretization is based on higher-order finite differences
on multi-block domains. Chemora's capabilities are demonstrated by simulations
of black hole collisions. This problem provides an acid test of the framework,
as the Einstein equations contain hundreds of variables and thousands of terms.Comment: 18 pages, 4 figures, accepted for publication in Scientific
Programmin
Introduction to MLML_DBASE Programs
The MLML DBASE family of programs described here provides many of the. algorithms used in oceanographic data reduction, general data manipulation and line graphs. These programs provide a consistent file structure for serial data typically encountered in oceanography. This introduction should provide enough general knowledge to explain the scope of the program and to run the basic MLML_DBASE programs. It is not
intended as a programmer's guide. (PDF contains 50 pages
FORM Matters: Fast Symbolic Computation under UNIX
We give a brief introduction to FORM, a symbolic programming language for
massive batch operations, designed by J.A.M. Vermaseren. In particular, we
stress various methods to efficiently use FORM under the UNIX operating system.
Several scripts and examples are given, and suggestions on how to use the vim
editor as development platform.Comment: 10 pages, PDF document (PDFLaTeX source available upon request) with
2 JPG figures; submitted to Computers & Mathematics with Application
GraphCombEx: A Software Tool for Exploration of Combinatorial Optimisation Properties of Large Graphs
We present a prototype of a software tool for exploration of multiple
combinatorial optimisation problems in large real-world and synthetic complex
networks. Our tool, called GraphCombEx (an acronym of Graph Combinatorial
Explorer), provides a unified framework for scalable computation and
presentation of high-quality suboptimal solutions and bounds for a number of
widely studied combinatorial optimisation problems. Efficient representation
and applicability to large-scale graphs and complex networks are particularly
considered in its design. The problems currently supported include maximum
clique, graph colouring, maximum independent set, minimum vertex clique
covering, minimum dominating set, as well as the longest simple cycle problem.
Suboptimal solutions and intervals for optimal objective values are estimated
using scalable heuristics. The tool is designed with extensibility in mind,
with the view of further problems and both new fast and high-performance
heuristics to be added in the future. GraphCombEx has already been successfully
used as a support tool in a number of recent research studies using
combinatorial optimisation to analyse complex networks, indicating its promise
as a research software tool
Systems Technology Laboratory (STL) compendium of utilities
Multipurpose programs, routines and operating systems are described. Data conversion and character string comparison subroutine are included. Graphics packages, and file maintenance programs are also included
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