!> @file random_gauss.f90 !------------------------------------------------------------------------------! ! This file is part of the PALM model system. ! ! 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 1997-2019 Leibniz Universitaet Hannover !------------------------------------------------------------------------------! ! ! Current revisions: ! ----------------- ! ! ! Former revisions: ! ----------------- ! $Id: random_gauss.f90 4182 2019-08-22 15:20:23Z suehring $ ! Corrected "Former revisions" section ! ! 3655 2019-01-07 16:51:22Z knoop ! Corrected "Former revisions" section ! ! 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