| 1 | MODULE random_function_mod |
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| 2 | !------------------------------------------------------------------------------! |
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| 3 | ! Current revisions: |
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| 4 | ! ----------------- |
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| 5 | ! |
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| 6 | ! |
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| 7 | ! Former revisions: |
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| 8 | ! ----------------- |
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| 9 | ! $Id: random_function.f90 484 2010-02-05 07:36:54Z helmke $ |
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| 10 | ! RCS Log replace by Id keyword, revision history cleaned up |
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| 11 | ! |
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| 12 | ! Revision 1.3 2003/10/29 09:06:57 raasch |
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| 13 | ! Former function changed to a module. |
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| 14 | ! |
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| 15 | ! Revision 1.1 1998/02/04 16:09:45 raasch |
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| 16 | ! Initial revision |
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| 17 | ! |
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| 18 | ! |
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| 19 | ! Description: |
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| 20 | ! ------------ |
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| 21 | ! Random number generator, produces numbers equally distributed in interval [0,1] |
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| 22 | ! This routine is taken from the "numerical recipies" |
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| 23 | !------------------------------------------------------------------------------! |
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| 24 | |
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| 25 | IMPLICIT NONE |
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| 26 | |
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| 27 | PRIVATE |
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| 28 | |
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| 29 | PUBLIC random_function, random_function_ini |
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| 30 | |
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| 31 | INTEGER, PUBLIC, SAVE :: random_iv(32), random_iy |
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| 32 | |
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| 33 | INTERFACE random_function_ini |
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| 34 | MODULE PROCEDURE random_function_ini |
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| 35 | END INTERFACE random_function_ini |
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| 36 | |
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| 37 | INTERFACE random_function |
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| 38 | MODULE PROCEDURE random_function |
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| 39 | END INTERFACE random_function |
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| 40 | |
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| 41 | CONTAINS |
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| 42 | |
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| 43 | SUBROUTINE random_function_ini |
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| 44 | |
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| 45 | IMPLICIT NONE |
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| 46 | |
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| 47 | random_iv = 0 |
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| 48 | random_iy = 0 |
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| 49 | |
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| 50 | END SUBROUTINE random_function_ini |
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| 51 | |
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| 52 | FUNCTION random_function( idum ) |
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| 53 | |
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| 54 | |
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| 55 | IMPLICIT NONE |
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| 56 | |
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| 57 | INTEGER :: ia, idum, im, iq, ir, ndiv, ntab |
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| 58 | REAL :: am, eps, random_function, ranf, rnmx |
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| 59 | |
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| 60 | PARAMETER ( ia=16807, im=2147483647, am=1.0/im, iq=127773, ir=2836, & |
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| 61 | ntab=32, ndiv=1+(im-1)/ntab, eps=1.2e-7, rnmx=1.0-eps ) |
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| 62 | |
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| 63 | INTEGER :: j, k |
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| 64 | |
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| 65 | |
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| 66 | IF ( idum .le. 0 .or. random_iy .eq. 0 ) THEN |
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| 67 | idum = max (-idum,1) |
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| 68 | DO j = ntab+8,1,-1 |
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| 69 | k = idum / iq |
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| 70 | idum = ia * ( idum - k * iq ) - ir * k |
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| 71 | IF ( idum .lt. 0 ) idum = idum + im |
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| 72 | IF ( j .le. ntab ) random_iv(j) = idum |
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| 73 | ENDDO |
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| 74 | random_iy = random_iv(1) |
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| 75 | ENDIF |
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| 76 | |
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| 77 | k = idum / iq |
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| 78 | idum = ia * ( idum - k * iq ) - ir * k |
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| 79 | IF ( idum .lt. 0 ) idum = idum + im |
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| 80 | j = 1 + random_iy / ndiv |
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| 81 | random_iy = random_iv(j) |
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| 82 | random_iv(j) = idum |
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| 83 | random_function = min ( am * random_iy , rnmx ) |
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| 84 | |
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| 85 | END FUNCTION random_function |
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| 86 | |
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| 87 | END MODULE random_function_mod |
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