!> @file random_gauss.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 1997-2016 Leibniz Universitaet Hannover !--------------------------------------------------------------------------------! ! ! Current revisions: ! ----------------- ! ! ! Former revisions: ! ----------------- ! $Id: random_gauss.f90 1818 2016-04-06 15:53:27Z suehring $ ! ! 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 ! ! 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 1998/03/25 20:09:47 raasch ! Initial revision ! ! ! Description: ! ------------ !> Generates a gaussian distributed random number (mean value 1, sigma = 1) !> This routine is taken from the "numerical recipies". !------------------------------------------------------------------------------! FUNCTION random_gauss( idum, upper_limit ) USE kinds USE random_function_mod, & ONLY: random_function IMPLICIT NONE INTEGER(iwp) :: idum !< INTEGER(iwp) :: iset !< REAL(wp) :: fac !< REAL(wp) :: gset !< REAL(wp) :: random_gauss !< REAL(wp) :: rsq !< REAL(wp) :: upper_limit !< REAL(wp) :: v1 !< REAL(wp) :: v2 !< SAVE iset, gset DATA iset /0/ ! !-- Random numbers are created as long as they do not fall below the given !-- upper limit DO IF ( iset == 0 ) THEN rsq = 0.0_wp DO WHILE ( rsq >= 1.0_wp .OR. rsq == 0.0_wp ) v1 = 2.0_wp * random_function( idum ) - 1.0_wp v2 = 2.0_wp * random_function( idum ) - 1.0_wp rsq = v1**2 + v2**2 ENDDO fac = SQRT( -2.0_wp * LOG( rsq ) / rsq ) gset = v1 * fac random_gauss = v2 * fac + 1.0_wp iset = 1 ELSE random_gauss = gset + 1.0_wp iset = 0 ENDIF IF ( ABS( random_gauss - 1.0_wp ) <= upper_limit ) EXIT ENDDO END FUNCTION random_gauss