105 lines
2.7 KiB
C
105 lines
2.7 KiB
C
/* Implementation of the IRAND, RAND, and SRAND intrinsics.
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Copyright (C) 2004 Free Software Foundation, Inc.
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Contributed by Steven G. Kargl <kargls@comcast.net>.
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This file is part of the GNU Fortran 95 runtime library (libgfortran).
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Libgfortran is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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Libgfortran is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with libgfor; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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/* Simple multiplicative congruent algorithm.
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The period of this generator is approximately 2^31-1, which means that
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it should not be used for anything serious. The implementation here
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is based of an algorithm from S.K. Park and K.W. Miller, Comm. ACM,
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31, 1192-1201 (1988). It is also provided solely for compatibility
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with G77. */
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#include "config.h"
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#include "libgfortran.h"
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#define GFC_RAND_A 16807
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#define GFC_RAND_M 2147483647
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#define GFC_RAND_M1 (GFC_RAND_M - 1)
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static GFC_UINTEGER_8 rand_seed = 1;
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/* Set the seed of the irand generator. Note 0 is a bad seed. */
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static void
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srand_internal (GFC_INTEGER_8 i)
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{
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rand_seed = i ? i : 123459876;
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}
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extern void PREFIX(srand) (GFC_INTEGER_4 *i);
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export_proto_np(PREFIX(srand));
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void
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PREFIX(srand) (GFC_INTEGER_4 *i)
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{
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srand_internal (*i);
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}
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/* Return an INTEGER in the range [1,GFC_RAND_M-1]. */
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extern GFC_INTEGER_4 irand (GFC_INTEGER_4 *);
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iexport_proto(irand);
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GFC_INTEGER_4
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irand (GFC_INTEGER_4 *i)
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{
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GFC_INTEGER_4 j;
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if (i)
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j = *i;
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else
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j = 0;
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switch (j)
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{
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/* Return the next RN. */
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case 0:
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break;
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/* Reset the RN sequence to system-dependent sequence and return the
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first value. */
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case 1:
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srand_internal (0);
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break;
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/* Seed the RN sequence with j and return the first value. */
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default:
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srand_internal (j);
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break;
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}
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rand_seed = GFC_RAND_A * rand_seed % GFC_RAND_M;
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return (GFC_INTEGER_4) rand_seed;
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}
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iexport(irand);
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/* Return a random REAL in the range [0,1). */
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extern GFC_REAL_4 PREFIX(rand) (GFC_INTEGER_4 *i);
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export_proto_np(PREFIX(rand));
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GFC_REAL_4
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PREFIX(rand) (GFC_INTEGER_4 *i)
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{
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return normalize_r4_i4 (irand (i) - 1, GFC_RAND_M1 - 1);
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}
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