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