1 | !> @file random_gauss.f90 |
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2 | !--------------------------------------------------------------------------------------------------! |
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3 | ! This file is part of the PALM model system. |
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4 | ! |
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5 | ! PALM is free software: you can redistribute it and/or modify it under the terms of the GNU General |
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6 | ! Public License as published by the Free Software Foundation, either version 3 of the License, or |
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7 | ! (at your option) any later version. |
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8 | ! |
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9 | ! PALM is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the |
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10 | ! implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General |
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11 | ! Public License for more details. |
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12 | ! |
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13 | ! You should have received a copy of the GNU General Public License along with PALM. If not, see |
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14 | ! <http://www.gnu.org/licenses/>. |
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15 | ! |
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16 | ! Copyright 1997-2021 Leibniz Universitaet Hannover |
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17 | !--------------------------------------------------------------------------------------------------! |
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18 | ! |
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19 | ! |
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20 | ! Current revisions: |
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21 | ! ----------------- |
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22 | ! |
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23 | ! |
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24 | ! Former revisions: |
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25 | ! ----------------- |
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26 | ! $Id: random_gauss.f90 4828 2021-01-05 11:21:41Z raasch $ |
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27 | ! File re-formatted to follow the PALM coding standard |
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28 | ! |
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29 | ! 4360 2020-01-07 11:25:50Z suehring |
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30 | ! Corrected "Former revisions" section |
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31 | ! |
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32 | ! 3655 2019-01-07 16:51:22Z knoop |
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33 | ! Corrected "Former revisions" section |
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34 | ! |
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35 | ! Revision 1.1 1998/03/25 20:09:47 raasch |
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36 | ! Initial revision |
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37 | ! |
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38 | ! |
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39 | !--------------------------------------------------------------------------------------------------! |
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40 | ! Description: |
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41 | ! ------------ |
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42 | !> Generates a gaussian distributed random number (mean value 1, sigma = 1) |
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43 | !> This routine is taken from the "numerical recipies". |
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44 | !--------------------------------------------------------------------------------------------------! |
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45 | FUNCTION random_gauss( idum, upper_limit ) |
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46 | |
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47 | |
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48 | USE kinds |
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49 | |
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50 | USE random_function_mod, & |
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51 | ONLY: random_function |
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52 | |
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53 | IMPLICIT NONE |
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54 | |
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55 | INTEGER(iwp) :: idum !< |
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56 | INTEGER(iwp) :: iset !< |
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57 | |
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58 | REAL(wp) :: fac !< |
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59 | REAL(wp) :: gset !< |
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60 | REAL(wp) :: random_gauss !< |
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61 | REAL(wp) :: rsq !< |
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62 | REAL(wp) :: upper_limit !< |
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63 | REAL(wp) :: v1 !< |
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64 | REAL(wp) :: v2 !< |
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65 | |
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66 | SAVE iset, gset |
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67 | |
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68 | DATA iset /0/ |
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69 | |
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70 | ! |
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71 | !-- Random numbers are created as long as they do not fall below the given upper limit |
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72 | DO |
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73 | |
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74 | IF ( iset == 0 ) THEN |
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75 | rsq = 0.0_wp |
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76 | DO WHILE ( rsq >= 1.0_wp .OR. rsq == 0.0_wp ) |
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77 | v1 = 2.0_wp * random_function( idum ) - 1.0_wp |
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78 | v2 = 2.0_wp * random_function( idum ) - 1.0_wp |
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79 | rsq = v1**2 + v2**2 |
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80 | ENDDO |
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81 | fac = SQRT( -2.0_wp * LOG( rsq ) / rsq ) |
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82 | gset = v1 * fac |
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83 | random_gauss = v2 * fac + 1.0_wp |
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84 | iset = 1 |
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85 | ELSE |
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86 | random_gauss = gset + 1.0_wp |
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87 | iset = 0 |
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88 | ENDIF |
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89 | |
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90 | IF ( ABS( random_gauss - 1.0_wp ) <= upper_limit ) EXIT |
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91 | |
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92 | ENDDO |
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93 | |
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94 | END FUNCTION random_gauss |
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