Hi,
now that I have changed the PRNG algorithm behind RANDOM_NUMBER, and
thus breaking compatibility (in the weak sense that the stream of
random numbers will be different), one might also do a few other minor
improvements.
The attached patch makes sure to always initialize the PRNG seed from
the OS (/dev/urandom or falling back to gettimeofday ^ getpid) so that
the random generator state is different every time one runs a program.
This is probably closer to what people intuitively expect, and if one
wants a constant seed, it's easy enough to do by explicitly calling
RANDOM_SEED.
Unless there are objections, I intend to commit this in a few days. Regtested on
x86_64-pc-linux-gnu.
libgfortran:
2016-08-16 Janne Blomqvist <j...@gcc.gnu.org>
* intrinsics/random.c (master_init): New variable.
(init_rand_state): Move below getosrandom (), maybe initialize
master_state.
(random_seed_i4): If called with no arguments, set master_init to
false, and reinitialize. If called with PUT=, set master_init to
true.
(random_seed_i8): Likewise.
testsuite:
2016-08-16 Janne Blomqvist <j...@gcc.gnu.org>
* gfortran.dg/random_4.f90: Initialize seed before using, handle
the last special seed value.
* gfortran.dg/random_7.f90: Use size for last array member instead
of hardcoded value.
--
Janne Blomqvist
diff --git a/gcc/testsuite/gfortran.dg/random_4.f90
b/gcc/testsuite/gfortran.dg/random_4.f90
index 416b17c..e60698f 100644
--- a/gcc/testsuite/gfortran.dg/random_4.f90
+++ b/gcc/testsuite/gfortran.dg/random_4.f90
@@ -6,8 +6,11 @@ program trs
integer, allocatable, dimension(:) :: seed, check
call test_random_seed(size)
allocate(seed(size),check(size))
+ seed = 42
call test_random_seed(put=seed)
call test_random_seed(get=check)
+ ! With xorshift1024* the last seed value is special
+ seed(size) = check(size)
if (any (seed /= check)) call abort
contains
subroutine test_random_seed(size, put, get)
diff --git a/gcc/testsuite/gfortran.dg/random_7.f90
b/gcc/testsuite/gfortran.dg/random_7.f90
index aafe346..8cd9c43 100644
--- a/gcc/testsuite/gfortran.dg/random_7.f90
+++ b/gcc/testsuite/gfortran.dg/random_7.f90
@@ -10,8 +10,9 @@ program trs
seed(:) = huge(seed) / 17
call test_random_seed(put=seed)
call test_random_seed(get=check)
- ! In the current implementation seed(17) is special
- seed(17) = check(17)
+ ! In the current xorshift1024* implementation the last seed value is
+ ! special
+ seed(size) = check(size)
if (any (seed /= check)) call abort
contains
subroutine test_random_seed(size, put, get)
diff --git a/libgfortran/intrinsics/random.c b/libgfortran/intrinsics/random.c
index 3b91389..35c7611 100644
--- a/libgfortran/intrinsics/random.c
+++ b/libgfortran/intrinsics/random.c
@@ -193,9 +193,10 @@ typedef struct
xorshift1024star_state;
-/* How many times we have jumped. This and master_state are the only
- variables protected by random_lock. */
-static unsigned njumps;
+/* master_init, njumps, and master_state are the only variables
+ protected by random_lock. */
+static bool master_init;
+static unsigned njumps; /* How many times we have jumped. */
static uint64_t master_state[] = {
0xad63fa1ed3b55f36ULL, 0xd94473e78978b497ULL, 0xbc60592a98172477ULL,
0xa3de7c6e81265301ULL, 0x586640c5e785af27ULL, 0x7a2a3f63b67ce5eaULL,
@@ -272,24 +273,6 @@ jump (xorshift1024star_state* rs)
}
-/* Initialize the random number generator for the current thread,
- using the master state and the number of times we must jump. */
-
-static void
-init_rand_state (xorshift1024star_state* rs, const bool locked)
-{
- if (!locked)
- __gthread_mutex_lock (&random_lock);
- memcpy (&rs->s, master_state, sizeof (master_state));
- unsigned n = njumps++;
- if (!locked)
- __gthread_mutex_unlock (&random_lock);
- for (unsigned i = 0; i < n; i++)
- jump (rs);
- rs->init = true;
-}
-
-
/* Super-simple LCG generator used in getosrandom () if /dev/urandom
doesn't exist. */
@@ -359,6 +342,30 @@ getosrandom (void *buf, size_t buflen)
}
+/* Initialize the random number generator for the current thread,
+ using the master state and the number of times we must jump. */
+
+static void
+init_rand_state (xorshift1024star_state* rs, const bool locked)
+{
+ if (!locked)
+ __gthread_mutex_lock (&random_lock);
+ if (!master_init)
+ {
+ getosrandom (master_state, sizeof (master_state));
+ njumps = 0;
+ master_init = true;
+ }
+ memcpy (&rs->s, master_state, sizeof (master_state));
+ unsigned n = njumps++;
+ if (!locked)
+ __gthread_mutex_unlock (&random_lock);
+ for (unsigned i = 0; i < n; i++)
+ jump (rs);
+ rs->init = true;
+}
+
+
/* This function produces a REAL(4) value from the uniform distribution
with range [0,1). */
@@ -791,8 +798,7 @@ random_seed_i4 (GFC_INTEGER_4 *size, gfc_array_i4 *put,
gfc_array_i4 *get)
a processor-dependent value to the seed." */
if (size == NULL && put == NULL && get == NULL)
{
- getosrandom (master_state, sizeof (master_state));
- njumps = 0;
+ master_init = false;
init_rand_state (rs, true);
}
@@ -816,6 +822,7 @@ random_seed_i4 (GFC_INTEGER_4 *size, gfc_array_i4 *put,
gfc_array_i4 *get)
provide seeds with quality only in the lower or upper part. */
scramble_seed ((unsigned char *) master_state, seed, sizeof seed);
njumps = 0;
+ master_init = true;
init_rand_state (rs, true);
rs->p = put->base_addr[SZ * GFC_DESCRIPTOR_STRIDE(put, 0)] & 15;
@@ -873,8 +880,7 @@ random_seed_i8 (GFC_INTEGER_8 *size, gfc_array_i8 *put,
gfc_array_i8 *get)
a processor-dependent value to the seed." */
if (size == NULL && put == NULL && get == NULL)
{
- getosrandom (master_state, sizeof (master_state));
- njumps = 0;
+ master_init = false;
init_rand_state (rs, true);
}
@@ -894,6 +900,7 @@ random_seed_i8 (GFC_INTEGER_8 *size, gfc_array_i8 *put,
gfc_array_i8 *get)
sizeof (GFC_UINTEGER_8));
njumps = 0;
+ master_init = true;
init_rand_state (rs, true);
rs->p = put->base_addr[SZ * GFC_DESCRIPTOR_STRIDE(put, 0)] & 15;
}
