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68 lines
2.4 KiB
C
68 lines
2.4 KiB
C
/*
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* $Id: stdlib_rand_r.c,v 1.2 2006-01-08 12:04:26 obarthel Exp $
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*
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* :ts=4
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*
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* Portable ISO 'C' (1994) runtime library for the Amiga computer
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* Copyright (c) 2002-2015 by Olaf Barthel <obarthel (at) gmx.net>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Neither the name of Olaf Barthel nor the names of contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef _STDLIB_HEADERS_H
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#include "stdlib_headers.h"
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#endif /* _STDLIB_HEADERS_H */
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/****************************************************************************/
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/* Parameters of a pseudo-random-number generator from Knuth's
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"The Art of Computer Programming, Volume 2: Seminumerical Algorithms"
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(3rd edition), pp. 185-186. */
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#define MM 2147483647 /* a Mersenne prime */
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#define AA 48271 /* this does well in the spectral test */
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#define QQ 44488 /* (long)(MM/AA) */
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#define RR 3399 /* MM % AA; it is important that RR < QQ */
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/****************************************************************************/
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int
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rand_r(unsigned int * seed)
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{
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int X;
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X = (int)((*seed) & 0x7fffffff);
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if(X == 0)
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X = 1; /* NOTE: for Knuth's algorithm the seed must not be zero. */
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X = AA * (X % QQ) - RR * (long)(X / QQ);
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if(X < 0)
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X += MM;
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(*seed) = (unsigned int)X;
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return(X);
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}
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