!> @file random_function_mod.f90 !------------------------------------------------------------------------------! ! This file is part of PALM. ! ! PALM 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. ! ! PALM 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. ! ! You should have received a copy of the GNU General Public License along with ! PALM. If not, see . ! ! Copyright 1997-2017 Leibniz Universitaet Hannover !------------------------------------------------------------------------------! ! ! Current revisions: ! ----------------- ! ! ! Former revisions: ! ----------------- ! $Id: random_function_mod.f90 2101 2017-01-05 16:42:31Z kanani $ ! ! 2000 2016-08-20 18:09:15Z knoop ! Forced header and separation lines into 80 columns ! ! 1850 2016-04-08 13:29:27Z maronga ! Module renamed ! ! ! 1682 2015-10-07 23:56:08Z knoop ! Code annotations made doxygen readable ! ! 1342 2014-03-26 17:04:47Z kanani ! REAL constants defined as wp-kind ! ! 1320 2014-03-20 08:40:49Z raasch ! ONLY-attribute added to USE-statements, ! kind-parameters added to all INTEGER and REAL declaration statements, ! kinds are defined in new module kinds, ! old module precision_kind is removed, ! revision history before 2012 removed, ! comment fields (!:) to be used for variable explanations added to ! all variable declaration statements ! ! 1092 2013-02-02 11:24:22Z raasch ! unused variables removed ! ! 1036 2012-10-22 13:43:42Z raasch ! code put under GPL (PALM 3.9) ! ! RCS Log replace by Id keyword, revision history cleaned up ! ! Revision 1.1 1998/02/04 16:09:45 raasch ! Initial revision ! ! ! Description: ! ------------ !> Random number generator, produces numbers equally distributed in interval [0,1] !> This routine is taken from the "numerical recipies" !------------------------------------------------------------------------------! MODULE random_function_mod USE kinds IMPLICIT NONE PRIVATE PUBLIC random_function, random_function_ini INTEGER(iwp), PUBLIC, SAVE :: random_iv(32) !< INTEGER(iwp), PUBLIC, SAVE :: random_iy !< INTERFACE random_function_ini MODULE PROCEDURE random_function_ini END INTERFACE random_function_ini INTERFACE random_function MODULE PROCEDURE random_function END INTERFACE random_function CONTAINS !------------------------------------------------------------------------------! ! Description: ! ------------ !> @todo Missing subroutine description. !------------------------------------------------------------------------------! SUBROUTINE random_function_ini IMPLICIT NONE random_iv = 0 random_iy = 0 END SUBROUTINE random_function_ini FUNCTION random_function( idum ) IMPLICIT NONE INTEGER(iwp) :: ia !< INTEGER(iwp) :: idum !< INTEGER(iwp) :: im !< INTEGER(iwp) :: iq !< INTEGER(iwp) :: ir !< INTEGER(iwp) :: ndiv !< INTEGER(iwp) :: ntab !< INTEGER(iwp) :: j !< INTEGER(iwp) :: k !< REAL(wp) :: am !< REAL(wp) :: eps !< REAL(wp) :: random_function !< REAL(wp) :: rnmx !< PARAMETER ( ia=16807, im=2147483647, am=1.0_wp/im, iq=127773, ir=2836, & ntab=32, ndiv=1+(im-1)/ntab, eps=1.2e-7_wp, rnmx=1.0_wp-eps ) IF ( idum .le. 0 .or. random_iy .eq. 0 ) THEN idum = max (-idum,1) DO j = ntab+8,1,-1 k = idum / iq idum = ia * ( idum - k * iq ) - ir * k IF ( idum .lt. 0 ) idum = idum + im IF ( j .le. ntab ) random_iv(j) = idum ENDDO random_iy = random_iv(1) ENDIF k = idum / iq idum = ia * ( idum - k * iq ) - ir * k IF ( idum .lt. 0 ) idum = idum + im j = 1 + random_iy / ndiv random_iy = random_iv(j) random_iv(j) = idum random_function = min ( am * random_iy , rnmx ) END FUNCTION random_function END MODULE random_function_mod