1 | MODULE random_function_mod |
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2 | |
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3 | !--------------------------------------------------------------------------------! |
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4 | ! This file is part of PALM. |
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5 | ! |
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6 | ! PALM is free software: you can redistribute it and/or modify it under the terms |
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7 | ! of the GNU General Public License as published by the Free Software Foundation, |
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8 | ! either version 3 of the License, or (at your option) any later version. |
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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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17 | ! Copyright 1997-2012 Leibniz University Hannover |
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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_function.f90 1036 2012-10-22 13:43:42Z raasch $ |
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27 | ! RCS Log replace by Id keyword, revision history cleaned up |
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28 | ! |
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29 | ! Revision 1.3 2003/10/29 09:06:57 raasch |
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30 | ! Former function changed to a module. |
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31 | ! |
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32 | ! Revision 1.1 1998/02/04 16:09:45 raasch |
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33 | ! Initial revision |
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34 | ! |
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35 | ! |
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36 | ! Description: |
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37 | ! ------------ |
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38 | ! Random number generator, produces numbers equally distributed in interval [0,1] |
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39 | ! This routine is taken from the "numerical recipies" |
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40 | !------------------------------------------------------------------------------! |
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41 | |
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42 | IMPLICIT NONE |
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43 | |
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44 | PRIVATE |
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45 | |
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46 | PUBLIC random_function, random_function_ini |
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47 | |
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48 | INTEGER, PUBLIC, SAVE :: random_iv(32), random_iy |
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49 | |
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50 | INTERFACE random_function_ini |
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51 | MODULE PROCEDURE random_function_ini |
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52 | END INTERFACE random_function_ini |
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53 | |
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54 | INTERFACE random_function |
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55 | MODULE PROCEDURE random_function |
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56 | END INTERFACE random_function |
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57 | |
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58 | CONTAINS |
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59 | |
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60 | SUBROUTINE random_function_ini |
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61 | |
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62 | IMPLICIT NONE |
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63 | |
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64 | random_iv = 0 |
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65 | random_iy = 0 |
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66 | |
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67 | END SUBROUTINE random_function_ini |
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68 | |
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69 | FUNCTION random_function( idum ) |
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70 | |
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71 | |
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72 | IMPLICIT NONE |
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73 | |
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74 | INTEGER :: ia, idum, im, iq, ir, ndiv, ntab |
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75 | REAL :: am, eps, random_function, ranf, rnmx |
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76 | |
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77 | PARAMETER ( ia=16807, im=2147483647, am=1.0/im, iq=127773, ir=2836, & |
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78 | ntab=32, ndiv=1+(im-1)/ntab, eps=1.2e-7, rnmx=1.0-eps ) |
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79 | |
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80 | INTEGER :: j, k |
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81 | |
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82 | |
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83 | IF ( idum .le. 0 .or. random_iy .eq. 0 ) THEN |
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84 | idum = max (-idum,1) |
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85 | DO j = ntab+8,1,-1 |
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86 | k = idum / iq |
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87 | idum = ia * ( idum - k * iq ) - ir * k |
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88 | IF ( idum .lt. 0 ) idum = idum + im |
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89 | IF ( j .le. ntab ) random_iv(j) = idum |
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90 | ENDDO |
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91 | random_iy = random_iv(1) |
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92 | ENDIF |
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93 | |
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94 | k = idum / iq |
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95 | idum = ia * ( idum - k * iq ) - ir * k |
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96 | IF ( idum .lt. 0 ) idum = idum + im |
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97 | j = 1 + random_iy / ndiv |
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98 | random_iy = random_iv(j) |
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99 | random_iv(j) = idum |
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100 | random_function = min ( am * random_iy , rnmx ) |
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101 | |
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102 | END FUNCTION random_function |
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103 | |
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104 | END MODULE random_function_mod |
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