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/* Implementation of the IRAND, RAND, and SRAND intrinsics.
Copyright (C) 2004-2022 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 General Public
License as published by the Free Software Foundation; either
version 3 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 General Public License for more details.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
/* 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 "libgfortran.h"
#include <gthr.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;
#ifdef __GTHREAD_MUTEX_INIT
static __gthread_mutex_t rand_seed_lock = __GTHREAD_MUTEX_INIT;
#else
static __gthread_mutex_t rand_seed_lock;
#endif
/* Set the seed of the irand generator. Note 0 is a bad seed. */
static void
srand_internal (GFC_INTEGER_8 i)
{
rand_seed = i ? i : 123459876;
}
extern void PREFIX(srand) (GFC_INTEGER_4 *i);
export_proto_np(PREFIX(srand));
void
PREFIX(srand) (GFC_INTEGER_4 *i)
{
__gthread_mutex_lock (&rand_seed_lock);
srand_internal (*i);
__gthread_mutex_unlock (&rand_seed_lock);
}
/* Return an INTEGER in the range [1,GFC_RAND_M-1]. */
extern GFC_INTEGER_4 irand (GFC_INTEGER_4 *);
iexport_proto(irand);
GFC_INTEGER_4
irand (GFC_INTEGER_4 *i)
{
GFC_INTEGER_4 j;
if (i)
j = *i;
else
j = 0;
__gthread_mutex_lock (&rand_seed_lock);
switch (j)
{
/* Return the next RN. */
case 0:
break;
/* Reset the RN sequence to system-dependent sequence and return the
first value. */
case 1:
srand_internal (0);
break;
/* Seed the RN sequence with j and return the first value. */
default:
srand_internal (j);
break;
}
rand_seed = GFC_RAND_A * rand_seed % GFC_RAND_M;
j = (GFC_INTEGER_4) rand_seed;
__gthread_mutex_unlock (&rand_seed_lock);
return j;
}
iexport(irand);
/* Return a random REAL in the range [0,1). */
extern GFC_REAL_4 PREFIX(rand) (GFC_INTEGER_4 *i);
export_proto_np(PREFIX(rand));
GFC_REAL_4
PREFIX(rand) (GFC_INTEGER_4 *i)
{
GFC_UINTEGER_4 mask;
#if GFC_REAL_4_RADIX == 2
mask = ~ (GFC_UINTEGER_4) 0u << (32 - GFC_REAL_4_DIGITS + 1);
#elif GFC_REAL_4_RADIX == 16
mask = ~ (GFC_UINTEGER_4) 0u << ((8 - GFC_REAL_4_DIGITS) * 4 + 1);
#else
#error "GFC_REAL_4_RADIX has unknown value"
#endif
return ((GFC_UINTEGER_4) (irand(i) -1) & mask) * (GFC_REAL_4) 0x1.p-31f;
}
#ifndef __GTHREAD_MUTEX_INIT
static void __attribute__((constructor))
init (void)
{
__GTHREAD_MUTEX_INIT_FUNCTION (&rand_seed_lock);
}
#endif
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