| /* Implementation of the IRAND, RAND, and SRAND intrinsics. |
| Copyright (C) 2004-2024 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 |