[1682] | 1 | !> @file random_gauss.f90 |
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[2000] | 2 | !------------------------------------------------------------------------------! |
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[2696] | 3 | ! This file is part of the PALM model system. |
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[1036] | 4 | ! |
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[2000] | 5 | ! PALM is free software: you can redistribute it and/or modify it under the |
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| 6 | ! terms of the GNU General Public License as published by the Free Software |
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| 7 | ! Foundation, either version 3 of the License, or (at your option) any later |
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| 8 | ! version. |
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[1036] | 9 | ! |
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| 10 | ! PALM is distributed in the hope that it will be useful, but WITHOUT ANY |
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| 11 | ! WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR |
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| 12 | ! A PARTICULAR PURPOSE. See the GNU General Public License for more details. |
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| 13 | ! |
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| 14 | ! You should have received a copy of the GNU General Public License along with |
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| 15 | ! PALM. If not, see <http://www.gnu.org/licenses/>. |
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| 16 | ! |
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[2718] | 17 | ! Copyright 1997-2018 Leibniz Universitaet Hannover |
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[2000] | 18 | !------------------------------------------------------------------------------! |
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[1036] | 19 | ! |
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[484] | 20 | ! Current revisions: |
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[1] | 21 | ! ----------------- |
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[1321] | 22 | ! |
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[2001] | 23 | ! |
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[1321] | 24 | ! Former revisions: |
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| 25 | ! ----------------- |
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| 26 | ! $Id: random_gauss.f90 2718 2018-01-02 08:49:38Z Giersch $ |
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[2716] | 27 | ! Corrected "Former revisions" section |
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| 28 | ! |
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| 29 | ! 2696 2017-12-14 17:12:51Z kanani |
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| 30 | ! Change in file header (GPL part) |
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[1321] | 31 | ! |
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[2716] | 32 | ! 2101 2017-01-05 16:42:31Z suehring |
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| 33 | ! |
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[2001] | 34 | ! 2000 2016-08-20 18:09:15Z knoop |
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| 35 | ! Forced header and separation lines into 80 columns |
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| 36 | ! |
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[1683] | 37 | ! 1682 2015-10-07 23:56:08Z knoop |
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| 38 | ! Code annotations made doxygen readable |
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| 39 | ! |
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[1343] | 40 | ! 1342 2014-03-26 17:04:47Z kanani |
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| 41 | ! REAL constants defined as wp-kind |
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| 42 | ! |
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[1321] | 43 | ! 1320 2014-03-20 08:40:49Z raasch |
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[1320] | 44 | ! ONLY-attribute added to USE-statements, |
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| 45 | ! kind-parameters added to all INTEGER and REAL declaration statements, |
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| 46 | ! kinds are defined in new module kinds, |
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| 47 | ! old module precision_kind is removed, |
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| 48 | ! revision history before 2012 removed, |
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| 49 | ! comment fields (!:) to be used for variable explanations added to |
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| 50 | ! all variable declaration statements |
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[1037] | 51 | ! |
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| 52 | ! 1036 2012-10-22 13:43:42Z raasch |
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| 53 | ! code put under GPL (PALM 3.9) |
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| 54 | ! |
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[3] | 55 | ! RCS Log replace by Id keyword, revision history cleaned up |
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| 56 | ! |
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[1] | 57 | ! Revision 1.1 1998/03/25 20:09:47 raasch |
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| 58 | ! Initial revision |
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| 59 | ! |
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| 60 | ! |
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| 61 | ! Description: |
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| 62 | ! ------------ |
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[1682] | 63 | !> Generates a gaussian distributed random number (mean value 1, sigma = 1) |
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| 64 | !> This routine is taken from the "numerical recipies". |
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[1] | 65 | !------------------------------------------------------------------------------! |
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[1682] | 66 | FUNCTION random_gauss( idum, upper_limit ) |
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| 67 | |
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[1] | 68 | |
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[1320] | 69 | USE kinds |
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[1] | 70 | |
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[1320] | 71 | USE random_function_mod, & |
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| 72 | ONLY: random_function |
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| 73 | |
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[1] | 74 | IMPLICIT NONE |
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| 75 | |
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[1682] | 76 | INTEGER(iwp) :: idum !< |
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| 77 | INTEGER(iwp) :: iset !< |
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[1] | 78 | |
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[1682] | 79 | REAL(wp) :: fac !< |
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| 80 | REAL(wp) :: gset !< |
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| 81 | REAL(wp) :: random_gauss !< |
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| 82 | REAL(wp) :: rsq !< |
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| 83 | REAL(wp) :: upper_limit !< |
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| 84 | REAL(wp) :: v1 !< |
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| 85 | REAL(wp) :: v2 !< |
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[1320] | 86 | |
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[1] | 87 | SAVE iset, gset |
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| 88 | |
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| 89 | DATA iset /0/ |
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| 90 | |
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| 91 | ! |
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| 92 | !-- Random numbers are created as long as they do not fall below the given |
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| 93 | !-- upper limit |
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| 94 | DO |
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| 95 | |
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| 96 | IF ( iset == 0 ) THEN |
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[1342] | 97 | rsq = 0.0_wp |
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| 98 | DO WHILE ( rsq >= 1.0_wp .OR. rsq == 0.0_wp ) |
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| 99 | v1 = 2.0_wp * random_function( idum ) - 1.0_wp |
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| 100 | v2 = 2.0_wp * random_function( idum ) - 1.0_wp |
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[1] | 101 | rsq = v1**2 + v2**2 |
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| 102 | ENDDO |
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[1342] | 103 | fac = SQRT( -2.0_wp * LOG( rsq ) / rsq ) |
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[1] | 104 | gset = v1 * fac |
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[1342] | 105 | random_gauss = v2 * fac + 1.0_wp |
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[1] | 106 | iset = 1 |
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| 107 | ELSE |
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[1342] | 108 | random_gauss = gset + 1.0_wp |
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[1] | 109 | iset = 0 |
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| 110 | ENDIF |
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| 111 | |
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[1342] | 112 | IF ( ABS( random_gauss - 1.0_wp ) <= upper_limit ) EXIT |
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[1] | 113 | |
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| 114 | ENDDO |
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| 115 | |
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| 116 | END FUNCTION random_gauss |
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