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re PR fortran/31234 (Thread-safety of random_number should be documented.)

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2007-04-12  Daniel Franke  <franke.daniel@gmail.com>

        PR fortran/31234
        * intrinsic.texi (RANDOM_SEED, RANDOM_NUMBER): New.

From-SVN: r123760
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Daniel Franke 2007-04-12 14:23:03 -04:00 • committed by Daniel Franke
parent e8a2534927
commit 5ab5907a2a
2 changed files with 71 additions and 6 deletions
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5
gcc/fortran/ChangeLog
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@ -1,3 +1,8 @@
2007-04-12 Daniel Franke <franke.daniel@gmail.com>
PR fortran/31234
* intrinsic.texi (RANDOM_SEED, RANDOM_NUMBER): New.
2007-04-12 Tobias Schlüter <tobi@gcc.gnu.org>
PR fortran/31266

72
gcc/fortran/intrinsic.texi
View file

@ -7614,10 +7614,11 @@ end program test_rand
@cindex @code{RANDOM_NUMBER} intrinsic
@cindex random numbers
Intrinsic implemented, documentation pending.
@table @asis
@item @emph{Description}:
Returns a single pseudorandom number or an array of pseudorandom numbers
from the uniform distribution over the range @math{ 0 \leq x < 1}.
@item @emph{Standard}:
F95 and later
@ -7625,9 +7626,31 @@ F95 and later
Elemental subroutine
@item @emph{Syntax}:
@code{RANDOM_NUMBER(HARVEST)}
@item @emph{Arguments}:
@item @emph{Return value}:
@multitable @columnfractions .15 .70
@item @var{HARVEST} @tab Shall be a scalar or an array of type @code{REAL(*)}.
@end multitable
@item @emph{Example}:
@smallexample
program test_random_number
REAL :: r(5,5)
CALL init_random_seed() ! see example of RANDOM_SEED
CALL RANDOM_NUMBER(r)
end program
@end smallexample
@item @emph{Note}:
The implemented random number generator is thread safe if used within
OpenMP directives, i. e. its state will be consistent while called from
multiple threads. Please note that the currently implemented KISS generator
does not create random numbers in parallel from multiple sources, but in
sequence from a single source. If your OpenMP-enabled application heavily
relies on random numbers, you should consider employing a dedicated parallel
random number generator instead.
@item @emph{See also}:
@ref{RANDOM_SEED}
@end table
@ -7639,10 +7662,15 @@ Elemental subroutine
@cindex @code{RANDOM_SEED} intrinsic
@cindex random numbers
Intrinsic implemented, documentation pending.
@table @asis
@item @emph{Description}:
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 based on the system's time.
@item @emph{Standard}:
F95 and later
@ -7650,9 +7678,41 @@ F95 and later
Subroutine
@item @emph{Syntax}:
@code{CALL RANDOM_SEED(SIZE, PUT, GET)}
@item @emph{Arguments}:
@item @emph{Return value}:
@multitable @columnfractions .15 .70
@item @var{SIZE} @tab (Optional) Shall be a scalar and of type default
@code{INTEGER}, with @code{INTENT(OUT)}. It specifies the minimum size
of the arrays used with the @var{PUT} and @var{GET} arguments.
@item @var{PUT} @tab (Optional) Shall be an array of type default
@code{INTEGER} and rank one. It is @code{INTENT(IN)} and the size of
the array must be larger than or equal to the number returned by the
@var{SIZE} argument.
@item @var{GET} @tab (Optional) Shall be an array of type default
@code{INTEGER} and rank one. It is @code{INTENT(OUT)} and the size
of the array must be larger than or equal to the number returned by
the @var{SIZE} argument.
@end multitable
@item @emph{Example}:
@smallexample
SUBROUTINE init_random_seed()
INTEGER :: i, n, clock
INTEGER, DIMENSION(:), ALLOCATABLE :: seed
CALL RANDOM_SEED(size = n)
ALLOCATE(seed(n))
CALL SYSTEM_CLOCK(COUNT=clock)
seed = clock + 37 * (/ (i - 1, i = 1, n) /)
CALL RANDOM_SEED(PUT = seed)
DEALLOCATE(seed)
END SUBROUTINE
@end smallexample
@item @emph{See also}:
@ref{RANDOM_NUMBER}
@end table