re PR fortran/63570 ([F2018] Implement 13.7.137 RANDOM INIT (REPEATABLE, IMAGE DISTINCT))

2018-06-01  Steven G. Kargl  <kargl@gcc.gnu.org>

	PR fortran/63570
	* check.c (gfc_check_random_init): New function. Check arguments of
	RANDOM_INIT.
	* gfortran.h (GFC_ISYM_RANDOM_INIT): New enum token.
	* intrinsic.c (add_subroutines): Add RANDOM_INIT to list of 
	subroutines.
	(gfc_check_intrinsic_standard): Introduce Fortran 2018 check.
	* intrinsic.h: Add prototypes for gfc_check_random_init and
	gfc_resolve_random_init
	* intrinsic.texi: Document new intrinsic subprogram.
	* iresolve.c (gfc_resolve_random_init): Resolve routine name.
	* trans-decl.c: Declare gfor_fndecl_random_init
	* trans-intrinsic.c (conv_intrinsic_random_init): New function.
	Translate call to RANDOM_INIT.
	(gfc_conv_intrinsic_subroutine): Call it.
 	* trans.h: Declare gfor_fndecl_random_init
 
2018-06-01  Steven G. Kargl  <kargl@gcc.gnu.org>
 
	PR fortran/63570
	* gfortran.dg/random_init_1.f90: New test.
	* gfortran.dg/random_init_2.f90: New test.
	* gfortran.dg/random_init_3.f90: New test.
	* gfortran.dg/random_init_4.f90: New test.
	* gfortran.dg/random_init_5.f90: New test.
	* gfortran.dg/random_init_6.f90: New test.

2018-06-01  Steven G. Kargl  <kargl@gcc.gnu.org>

	PR fortran/63570
	* libgfortran/Makefile.am: Add random_init.f90 to build.
	* libgfortran/Makefile.in: Regenerated.
	* libgfortran/gfortran.map: Expose symbol for _gfortran_random_init.
	* libgfortran/intrinsics/random_init.f90: Implementation.

From-SVN: r261075

1 files changed, 94 insertions, 0 deletions

diff --git a/libgfortran/intrinsics/random_init.f90 b/libgfortran/intrinsics/random_init.f90
new file mode 100644
index 00000000000..edea0b89c4e
--- /dev/null
+++ b/libgfortran/intrinsics/random_init.f90
@@ -0,0 +1,94 @@
+! Copyright (C) 2018 Free Software Foundation, Inc.
+! Contributed by Steven G. Kargl <kargl@gcc.gnu.org>
+! 
+! This file is part of the GNU Fortran 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/>.
+!
+!
+! WARNING:  This file should never be compiled with an option that changes
+! default logical kind from 4 to some other value or changes default integer
+! kind from from 4 to some other value.
+!
+!
+! There are four combinations of repeatable and image_distinct.  If a program
+! is compiled without the -fcoarray= option or with -fcoarray=single, then
+! execution of the compiled executable does not use image_distinct as it is
+! irrelevant (although required).  The behavior is as follows:
+!
+! call random_init(.true., .true.)
+!
+! The sequence of random numbers is repeatable within an instance of program
+! execution.  That is, calls to random_init(.true., .true.) during the
+! execution will reset the sequence of RN to the same sequence.  If the
+! program is compiled with -fcoarray=lib and multiple images are instantiated,
+! then each image accesses a repeatable distinct sequence of random numbers.
+! There are no guarantees that multiple execution of the program will access
+! the same sequence.
+!
+! call random_init(.false., .false.)
+! call random_init(.false., .true.)
+!
+! The sequence of random numbers is determined from process-dependent seeds.
+! On each execution of the executable, different seeds will be used.  For
+! -fcoarray=lib and multiple instantiated images, each image will use
+! process-dependent seeds.  In other words, the two calls have identical
+! behavior.
+!
+! call random_init(.true., .false.)
+! 
+! For a program compiled without the -fcoarray= option or with
+! -fcoarray=single, a single image is instantiated when the executable is
+! run.  If the executable causes multiple images to be instantiated, then
+! image_distinct=.false. in one image cannot affect the sequence of random
+! numbers in another image.  As gfortran gives each image its own independent
+! PRNG, this condition is automatically satisfied.
+!
+impure subroutine _gfortran_random_init(repeatable, image_distinct, hidden) 
+
+   implicit none
+
+   logical, value, intent(in) :: repeatable
+   logical, value, intent(in) :: image_distinct
+   integer, value, intent(in) :: hidden
+
+   logical, save :: once = .true.
+   integer :: nseed
+   integer, save, allocatable :: seed(:)
+
+   if (once) then
+      once = .false.
+      call random_seed(size=nseed)
+      allocate(seed(nseed))
+      call random_seed(get=seed)
+      !
+      ! To guarantee that seed is distinct on multiple images, add the hidden
+      ! argument (which is the image index).
+      !
+      if (image_distinct) seed = seed + hidden
+   end if
+
+   if (repeatable) then
+      call random_seed(put=seed);
+   else
+      call random_seed();
+   end if
+
+end subroutine _gfortran_random_init