102 lines
3.4 KiB
C
102 lines
3.4 KiB
C
/*BHEADER**********************************************************************
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* Copyright (c) 2006 The Regents of the University of California.
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* Produced at the Lawrence Livermore National Laboratory.
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* Written by the HYPRE team, UCRL-CODE-222953.
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* All rights reserved.
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*
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* This file is part of HYPRE (see http://www.llnl.gov/CASC/hypre/).
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* Please see the COPYRIGHT_and_LICENSE file for the copyright notice,
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* disclaimer and the GNU Lesser General Public License.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License (as published by the Free
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* Software Foundation) version 2.1 dated February 1999.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the IMPLIED WARRANTY OF MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the terms and conditions of the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* $Revision$
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***********************************************************************EHEADER*/
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/******************************************************************************
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*
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* This file contains routines that implement a pseudo-random number generator
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* detailed in the following paper.
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*
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* @article{RNG_Park_Miller,
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* author = {S. K. Park and K. W. Miller},
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* title = {Random number generators: good ones are hard to find},
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* journal = {Commun. ACM},
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* volume = {31},
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* number = {10},
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* year = {1988},
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* pages = {1192--1201},
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* }
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*
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* This RNG has been shown to appear fairly random, it is a full period
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* generating function (the sequence uses all of the values available to it up
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* to 2147483647), and can be implemented on any architecture using 32-bit
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* integers. The implementation in this file will not overflow for 32-bit
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* arithmetic, which all modern computers should support.
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*
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* @author David Alber
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* @date March 2005
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*
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*****************************************************************************/
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/*--------------------------------------------------------------------------
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* Static variables
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*--------------------------------------------------------------------------*/
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static int Seed = 13579;
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#define a 16807
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#define m 2147483647
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#define q 127773
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#define r 2836
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/*--------------------------------------------------------------------------
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* Initializes the pseudo-random number generator to a place in the sequence.
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*
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* @param seed an int containing the seed for the RNG.
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*--------------------------------------------------------------------------*/
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void hypre_SeedRand( int seed )
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{
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Seed = seed;
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}
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/*--------------------------------------------------------------------------
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* Computes the next pseudo-random number in the sequence using the global
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* variable Seed.
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*
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* @return a double containing the next number in the sequence divided by
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* 2147483647 so that the numbers are in (0, 1].
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*--------------------------------------------------------------------------*/
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double hypre_Rand()
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{
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int low, high, test;
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high = Seed / q;
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low = Seed % q;
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test = a * low - r * high;
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if(test > 0)
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{
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Seed = test;
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}
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else
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{
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Seed = test + m;
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}
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return ((double)(Seed) / m);
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}
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