readme.omc

openmp版的banchmark

/***********************************************************************
*
*                    NAS Parallel Benchmarks 2.3
*
*                         OpenMP C Versions
*
*                    Omni OpenMP Compiler Project
*                  Real World Computing Partnership
*
*                          October 18, 2000
*
***********************************************************************/

1. Introduction

The OpenMP C versions of the NAS Parallel Benchmarks are derived from
the serial Fortran versions of the NAS Parallel Benchmarks 2.3(NPB2.3-serial).
The objectives of the development of the OpenMP C versions are

  (1) Performance evaluation of numerical OpenMP C codes, and
  (2) Comparison of the performance of OpenMP C and OpenMP Fortran codes.

The OpenMP C versions can be used in the same way as NPB2.3-serial.
This suite is developed by Real World Computing Partnership as a part of
Omni OpenMP compiler project, and it is based on the work done by NAS.

This suite is just a sample implementation of NPB in OpenMP C.
Further optimizations for each platform, especially for DSMs, may be needed
to obtaining the maximum performance.

This document describes overview of the translation and parallelization,
installation of the suite, and so on.


2. Translation to C

We first translated Fortran codes in NPB2.3-serial to C codes by hand,
and then parallelized with OpenMP API.
Off course, Fortran codes can be translated to C automatically using
translators such as f2c. However, the automatically generated C codes 
may not have characteristics similar to hand-codes ones.

Note that the integer sort program, IS, in NPB2.3-serial is already
written in C and no translation is made for it.

The following are guidelines for the translation:

- Parameters are passed by value if it is possible.
- For making the lower bound of an array to be zero, subscripts are added
  minus one or an extra array element is added if necessary.
- The order of subscripts or the order of loop nests are changed, since
  Fortran and C have different storage order for arrays.
- Control transfer using goto statements are rewritten by using structured
  control constructs.
- In BT, LU and SP, source files are merged into a single file.
- In MG, the arrays for grids are allocated dynamically.
  This incurs performance losses due to extra memory accesses for
  pointer dereferences and poor memory access locality.
  In function comm3, copies via buffers are removed.


3. Parallelization with OpenMP API

The following are guidelines for the parallelization:

- Parallelize as coarse as possible to reduce fork-join overheads.
- Add nowait clauses as many as possible to reduce redundant synchronization.
- No specific scheduling policy is assumed if the schedule clause is not used.
- Minimum change to sequential code.
- Avoid the use of the runtime library routines.
- In LU, pipelined algorithm is used for wavefront computations.


4. Installation

If you have gzip'ed tar file 'NPB2.3-omp-C.tgz' or tar file 'NPB2.3-omp-C.tar',
unpack it first.
In directory "NPB2.3-omp-C", you will find the following files/directories:

  README.omc - this file
  README.org - readme file in NPB2.3-serial
  Makefile - makefile for the suite
  Doc - documentations (not modified from NPB2.3-serial)
  BT, CG, EP, FT, IS, LU, MG, SP - directory for each program
  bin - directory to put executable files
  common - common routines
  config - configuration files used by 'make'
  sys - utilities 

Some files in the suite are the same as those in NPB2.3-serial,
and some others have Fortran counterpart in NPB2.3-serial.

To use the suite, first edit file 'make.def' in directory 'config'.
You must specify the name of compiler and linker, and compiler options.
Definitions for Fortran are not used in this suite.
Then you can build benchmarks with 'make'.
For more details, refer to file "README.install" in subdirectory "Doc".


5. Information

- RWCP

  Information on the OpenMP C versions and the Omni OpenMP compiler is 
  available at http://pdplab.trc.rwcp.or.jp/pdperf/Omni/.
  Send comments and questions to [e-mail].

- NAS

  Information on the NAS Parallel Benchmarks is available at
  http://www.nas.nasa.gov/NAS/NPB/.
  Note that NAS does not support the OpenMP C versions.

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