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Commit b152f5a2 by Janne Blomqvist
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Replace KISS PRNG with xorshift1024* using per-thread state. 

frontend:

2016-08-11  Janne Blomqvist  <jb@gcc.gnu.org>

	* check.c (gfc_check_random_seed): Use new seed size in check.
	* intrinsic.texi (RANDOM_NUMBER): Updated documentation.
	(RANDOM_SEED): Likewise.


testsuite:

2016-08-11  Janne Blomqvist  <jb@gcc.gnu.org>

	* gfortran.dg/random_7.f90: Take into account that the last seed
	value is the special p value.
	* gfortran.dg/random_seed_1.f90: Seed size is now constant.


libgfortran:
2016-08-11  Janne Blomqvist  <jb@gcc.gnu.org>

	* intrinsics/random.c: Replace KISS with xorshift1024* using
	per-thread state.
	* runtime/main.c (init): Don't call random_seed_i4.

From-SVN: r239356
parent bb7ebad1
Showing with 63 additions and 98 deletions
gcc/fortran/ChangeLog
2016-08-11 Janne Blomqvist <jb@gcc.gnu.org>
* check.c (gfc_check_random_seed): Use new seed size in check.
* intrinsic.texi (RANDOM_NUMBER): Updated documentation.
(RANDOM_SEED): Likewise.
2016-08-08 Jakub Jelinek <jakub@redhat.com>
PR fortran/72716
......
gcc/fortran/check.c
......@@ -5527,16 +5527,14 @@ gfc_check_random_number (gfc_expr *harvest)
bool
gfc_check_random_seed (gfc_expr *size, gfc_expr *put, gfc_expr *get)
{
unsigned int nargs = 0, kiss_size;
unsigned int nargs = 0, seed_size;
locus *where = NULL;
mpz_t put_size, get_size;
bool have_gfc_real_16; /* Try and mimic HAVE_GFC_REAL_16 in libgfortran. */
have_gfc_real_16 = gfc_validate_kind (BT_REAL, 16, true) != -1;
/* Keep the number of bytes in sync with kiss_size in
libgfortran/intrinsics/random.c. */
kiss_size = (have_gfc_real_16 ? 48 : 32) / gfc_default_integer_kind;
/* Keep the number of bytes in sync with master_state in
libgfortran/intrinsics/random.c. +1 due to the integer p which is
part of the state too. */
seed_size = 128 / gfc_default_integer_kind + 1;
if (size != NULL)
{
......@@ -5579,11 +5577,11 @@ gfc_check_random_seed (gfc_expr *size, gfc_expr *put, gfc_expr *get)
return false;
if (gfc_array_size (put, &put_size)
&& mpz_get_ui (put_size) < kiss_size)
&& mpz_get_ui (put_size) < seed_size)
gfc_error ("Size of %qs argument of %qs intrinsic at %L "
"too small (%i/%i)",
gfc_current_intrinsic_arg[1]->name, gfc_current_intrinsic,
where, (int) mpz_get_ui (put_size), kiss_size);
where, (int) mpz_get_ui (put_size), seed_size);
}
if (get != NULL)
......@@ -5611,11 +5609,11 @@ gfc_check_random_seed (gfc_expr *size, gfc_expr *put, gfc_expr *get)
return false;
if (gfc_array_size (get, &get_size)
&& mpz_get_ui (get_size) < kiss_size)
&& mpz_get_ui (get_size) < seed_size)
gfc_error ("Size of %qs argument of %qs intrinsic at %L "
"too small (%i/%i)",
gfc_current_intrinsic_arg[2]->name, gfc_current_intrinsic,
where, (int) mpz_get_ui (get_size), kiss_size);
where, (int) mpz_get_ui (get_size), seed_size);
}
/* RANDOM_SEED may not have more than one non-optional argument. */
......
gcc/fortran/intrinsic.texi
......@@ -11126,23 +11126,16 @@ end program test_rand
Returns a single pseudorandom number or an array of pseudorandom numbers
from the uniform distribution over the range @math{ 0 \leq x < 1}.
The runtime-library implements George Marsaglia's KISS (Keep It Simple
Stupid) random number generator (RNG). This RNG combines:
@enumerate
@item The congruential generator @math{x(n) = 69069 \cdot x(n-1) + 1327217885}
with a period of @math{2^{32}},
@item A 3-shift shift-register generator with a period of @math{2^{32} - 1},
@item Two 16-bit multiply-with-carry generators with a period of
@math{597273182964842497 > 2^{59}}.
@end enumerate
The overall period exceeds @math{2^{123}}.
The runtime-library implements the xorshift1024* random number
generator (RNG). This generator has a period of @math{2^{1024} - 1},
and when using multiple threads up to @math{2^{512}} threads can each
generate @math{2^{512}} random numbers before any aliasing occurs.
Note that in a multi-threaded program (e.g. using OpenMP directives),
each thread will have its own random number state. For details of the
seeding procedure, see the documentation for the @code{RANDOM_SEED}
intrinsic.
Please note, this RNG is thread safe if used within OpenMP directives,
i.e., its state will be consistent while called from multiple threads.
However, the KISS generator does not create random numbers in parallel
from multiple sources, but in sequence from a single source. If an
OpenMP-enabled application heavily relies on random numbers, one should
consider employing a dedicated parallel random number generator instead.
@item @emph{Standard}:
Fortran 95 and later
......@@ -11184,12 +11177,23 @@ end program
Restarts or queries the state of the pseudorandom number generator used by
@code{RANDOM_NUMBER}.
If @code{RANDOM_SEED} is called without arguments, it is initialized
to a default state. The example below shows how to initialize the
random seed with a varying seed in order to ensure a different random
number sequence for each invocation of the program. Note that setting
any of the seed values to zero should be avoided as it can result in
poor quality random numbers being generated.
If @code{RANDOM_SEED} is called without arguments, it is seeded with
random data retrieved from the operating system.
As an extension to the Fortran standard, the GFortran
@code{RANDOM_NUMBER} supports multiple threads. Each thread in a
multi-threaded program has its own seed. When @code{RANDOM_SEED} is
called either without arguments or with the @var{PUT} argument, the
given seed is copied into a master seed as well as the seed of the
current thread. When a new thread uses @code{RANDOM_NUMBER} for the
first time, the seed is copied from the master seed, and forwarded
@math{N * 2^{512}} steps to guarantee that the random stream does not
alias any other stream in the system, where @var{N} is the number of
threads that have used @code{RANDOM_NUMBER} so far during the program
execution.
Note that setting any of the seed values to zero should be avoided as
it can result in poor quality random numbers being generated.
@item @emph{Standard}:
Fortran 95 and later
......@@ -11217,57 +11221,16 @@ the @var{SIZE} argument.
@item @emph{Example}:
@smallexample
subroutine init_random_seed()
use iso_fortran_env, only: int64
program test_random_seed
implicit none
integer, allocatable :: seed(:)
integer :: i, n, un, istat, dt(8), pid
integer(int64) :: t
integer :: n
call random_seed(size = n)
allocate(seed(n))
! First try if the OS provides a random number generator
open(newunit=un, file="/dev/urandom", access="stream", &
form="unformatted", action="read", status="old", iostat=istat)
if (istat == 0) then
read(un) seed
close(un)
else
! Fallback to XOR:ing the current time and pid. The PID is
! useful in case one launches multiple instances of the same
! program in parallel.
call system_clock(t)
if (t == 0) then
call date_and_time(values=dt)
t = (dt(1) - 1970) * 365_int64 * 24 * 60 * 60 * 1000 &
+ dt(2) * 31_int64 * 24 * 60 * 60 * 1000 &
+ dt(3) * 24_int64 * 60 * 60 * 1000 &
+ dt(5) * 60 * 60 * 1000 &
+ dt(6) * 60 * 1000 + dt(7) * 1000 &
+ dt(8)
end if
pid = getpid()
t = ieor(t, int(pid, kind(t)))
do i = 1, n
seed(i) = lcg(t)
end do
end if
call random_seed(put=seed)
contains
! This simple PRNG might not be good enough for real work, but is
! sufficient for seeding a better PRNG.
function lcg(s)
integer :: lcg
integer(int64) :: s
if (s == 0) then
s = 104729
else
s = mod(s, 4294967296_int64)
end if
s = mod(s * 279470273_int64, 4294967291_int64)
lcg = int(mod(s, int(huge(0), int64)), kind(0))
end function lcg
end subroutine init_random_seed
call random_seed(get=seed)
write (*, *) seed
end program test_random_seed
@end smallexample
@item @emph{See also}:
......
gcc/testsuite/ChangeLog
2016-08-11 Janne Blomqvist <jb@gcc.gnu.org>
* gfortran.dg/random_7.f90: Take into account that the last seed
value is the special p value.
* gfortran.dg/random_seed_1.f90: Seed size is now constant.
2016-08-11 Richard Biener <rguenther@suse.de>
* gcc.dg/tree-ssa/ssa-dom-thread-7.c: Adjust.
......
gcc/testsuite/gfortran.dg/random_7.f90
......@@ -10,8 +10,8 @@ program trs
seed(:) = huge(seed) / 17
call test_random_seed(put=seed)
call test_random_seed(get=check)
print *, seed
print *, check
! In the current implementation seed(17) is special
seed(17) = check(17)
if (any (seed /= check)) call abort
contains
subroutine test_random_seed(size, put, get)
......
gcc/testsuite/gfortran.dg/random_seed_1.f90
......@@ -3,10 +3,6 @@
! Emit a diagnostic for too small PUT array at compile time
! See PR fortran/37159
! Possible improvement:
! Provide a separate testcase for systems that support REAL(16),
! to test the minimum size of 12 (instead of 8).
!
! Updated to check for arrays of unexpected size,
! this also works for -fdefault-integer-8.
!
......@@ -14,19 +10,11 @@
PROGRAM random_seed_1
IMPLICIT NONE
! Find out what the's largest kind size
INTEGER, PARAMETER :: k1 = kind (0.d0)
INTEGER, PARAMETER :: &
k2 = max (k1, selected_real_kind (precision (0._k1) + 1))
INTEGER, PARAMETER :: &
k3 = max (k2, selected_real_kind (precision (0._k2) + 1))
INTEGER, PARAMETER :: &
k4 = max (k3, selected_real_kind (precision (0._k3) + 1))
INTEGER, PARAMETER :: nbytes = MERGE(48, 32, k4 == 16)
INTEGER, PARAMETER :: nbytes = 128
! +1 due to the special 'p' value in xorshift1024*
! '+1' to avoid out-of-bounds warnings
INTEGER, PARAMETER :: n = nbytes / KIND(n) + 1
INTEGER, PARAMETER :: n = nbytes / KIND(n) + 2
INTEGER, DIMENSION(n) :: seed
! Get seed, array too small
......
libgfortran/ChangeLog
2016-08-11 Janne Blomqvist <jb@gcc.gnu.org>
* intrinsics/random.c: Replace KISS with xorshift1024* using
per-thread state.
* runtime/main.c (init): Don't call random_seed_i4.
2016-07-22 Andre Vehreschild <vehre@gcc.gnu.org>
* caf/libcaf.h: Add parameter stat to caf_get() and
......
libgfortran/runtime/main.c
......@@ -119,8 +119,6 @@ init (void)
set_fpu ();
init_compile_options ();
random_seed_i4 (NULL, NULL, NULL);
}
......
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