| 1 | MODULE random_function_mod |
|---|
| 2 | !-------------------------------------------------------------------------------! |
|---|
| 3 | ! Actual revisions: |
|---|
| 4 | ! ----------------- |
|---|
| 5 | ! |
|---|
| 6 | ! |
|---|
| 7 | ! Former revisions: |
|---|
| 8 | ! ----------------- |
|---|
| 9 | ! $Log: random_function.f90,v $ |
|---|
| 10 | ! Revision 1.3 2003/10/29 09:06:57 raasch |
|---|
| 11 | ! Former function changed to a module. |
|---|
| 12 | ! |
|---|
| 13 | ! Revision 1.2 2001/01/22 08:00:23 raasch |
|---|
| 14 | ! Comments translated into English |
|---|
| 15 | ! |
|---|
| 16 | ! Revision 1.1 1998/02/04 16:09:45 raasch |
|---|
| 17 | ! Initial revision |
|---|
| 18 | ! |
|---|
| 19 | ! |
|---|
| 20 | ! Description: |
|---|
| 21 | ! ------------ |
|---|
| 22 | ! Random number generator, produces numbers equally distributed in interval [0,1] |
|---|
| 23 | ! This routine is taken from the "numerical recipies" |
|---|
| 24 | !-------------------------------------------------------------------------------! |
|---|
| 25 | |
|---|
| 26 | IMPLICIT NONE |
|---|
| 27 | |
|---|
| 28 | PRIVATE |
|---|
| 29 | |
|---|
| 30 | PUBLIC random_function, random_function_ini |
|---|
| 31 | |
|---|
| 32 | INTEGER, PUBLIC, SAVE :: random_iv(32), random_iy |
|---|
| 33 | |
|---|
| 34 | INTERFACE random_function_ini |
|---|
| 35 | MODULE PROCEDURE random_function_ini |
|---|
| 36 | END INTERFACE random_function_ini |
|---|
| 37 | |
|---|
| 38 | INTERFACE random_function |
|---|
| 39 | MODULE PROCEDURE random_function |
|---|
| 40 | END INTERFACE random_function |
|---|
| 41 | |
|---|
| 42 | CONTAINS |
|---|
| 43 | |
|---|
| 44 | SUBROUTINE random_function_ini |
|---|
| 45 | |
|---|
| 46 | IMPLICIT NONE |
|---|
| 47 | |
|---|
| 48 | random_iv = 0 |
|---|
| 49 | random_iy = 0 |
|---|
| 50 | |
|---|
| 51 | END SUBROUTINE random_function_ini |
|---|
| 52 | |
|---|
| 53 | FUNCTION random_function( idum ) |
|---|
| 54 | |
|---|
| 55 | |
|---|
| 56 | IMPLICIT NONE |
|---|
| 57 | |
|---|
| 58 | INTEGER :: ia, idum, im, iq, ir, ndiv, ntab |
|---|
| 59 | REAL :: am, eps, random_function, ranf, rnmx |
|---|
| 60 | |
|---|
| 61 | PARAMETER ( ia=16807, im=2147483647, am=1.0/im, iq=127773, ir=2836, & |
|---|
| 62 | ntab=32, ndiv=1+(im-1)/ntab, eps=1.2e-7, rnmx=1.0-eps ) |
|---|
| 63 | |
|---|
| 64 | INTEGER :: j, k |
|---|
| 65 | |
|---|
| 66 | |
|---|
| 67 | IF ( idum .le. 0 .or. random_iy .eq. 0 ) THEN |
|---|
| 68 | idum = max (-idum,1) |
|---|
| 69 | DO j = ntab+8,1,-1 |
|---|
| 70 | k = idum / iq |
|---|
| 71 | idum = ia * ( idum - k * iq ) - ir * k |
|---|
| 72 | IF ( idum .lt. 0 ) idum = idum + im |
|---|
| 73 | IF ( j .le. ntab ) random_iv(j) = idum |
|---|
| 74 | ENDDO |
|---|
| 75 | random_iy = random_iv(1) |
|---|
| 76 | ENDIF |
|---|
| 77 | |
|---|
| 78 | k = idum / iq |
|---|
| 79 | idum = ia * ( idum - k * iq ) - ir * k |
|---|
| 80 | IF ( idum .lt. 0 ) idum = idum + im |
|---|
| 81 | j = 1 + random_iy / ndiv |
|---|
| 82 | random_iy = random_iv(j) |
|---|
| 83 | random_iv(j) = idum |
|---|
| 84 | random_function = min ( am * random_iy , rnmx ) |
|---|
| 85 | |
|---|
| 86 | END FUNCTION random_function |
|---|
| 87 | |
|---|
| 88 | END MODULE random_function_mod |
|---|
