1 | MODULE random_function_mod |
---|
2 | |
---|
3 | !--------------------------------------------------------------------------------! |
---|
4 | ! This file is part of PALM. |
---|
5 | ! |
---|
6 | ! PALM is free software: you can redistribute it and/or modify it under the terms |
---|
7 | ! of the GNU General Public License as published by the Free Software Foundation, |
---|
8 | ! either version 3 of the License, or (at your option) any later version. |
---|
9 | ! |
---|
10 | ! PALM is distributed in the hope that it will be useful, but WITHOUT ANY |
---|
11 | ! WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR |
---|
12 | ! A PARTICULAR PURPOSE. See the GNU General Public License for more details. |
---|
13 | ! |
---|
14 | ! You should have received a copy of the GNU General Public License along with |
---|
15 | ! PALM. If not, see <http://www.gnu.org/licenses/>. |
---|
16 | ! |
---|
17 | ! Copyright 1997-2012 Leibniz University Hannover |
---|
18 | !--------------------------------------------------------------------------------! |
---|
19 | ! |
---|
20 | ! Current revisions: |
---|
21 | ! ----------------- |
---|
22 | ! |
---|
23 | ! |
---|
24 | ! Former revisions: |
---|
25 | ! ----------------- |
---|
26 | ! $Id: random_function.f90 1093 2013-02-02 12:58:49Z witha $ |
---|
27 | ! |
---|
28 | ! 1092 2013-02-02 11:24:22Z raasch |
---|
29 | ! unused variables removed |
---|
30 | ! |
---|
31 | ! 1036 2012-10-22 13:43:42Z raasch |
---|
32 | ! code put under GPL (PALM 3.9) |
---|
33 | ! |
---|
34 | ! RCS Log replace by Id keyword, revision history cleaned up |
---|
35 | ! |
---|
36 | ! Revision 1.3 2003/10/29 09:06:57 raasch |
---|
37 | ! Former function changed to a module. |
---|
38 | ! |
---|
39 | ! Revision 1.1 1998/02/04 16:09:45 raasch |
---|
40 | ! Initial revision |
---|
41 | ! |
---|
42 | ! |
---|
43 | ! Description: |
---|
44 | ! ------------ |
---|
45 | ! Random number generator, produces numbers equally distributed in interval [0,1] |
---|
46 | ! This routine is taken from the "numerical recipies" |
---|
47 | !------------------------------------------------------------------------------! |
---|
48 | |
---|
49 | IMPLICIT NONE |
---|
50 | |
---|
51 | PRIVATE |
---|
52 | |
---|
53 | PUBLIC random_function, random_function_ini |
---|
54 | |
---|
55 | INTEGER, PUBLIC, SAVE :: random_iv(32), random_iy |
---|
56 | |
---|
57 | INTERFACE random_function_ini |
---|
58 | MODULE PROCEDURE random_function_ini |
---|
59 | END INTERFACE random_function_ini |
---|
60 | |
---|
61 | INTERFACE random_function |
---|
62 | MODULE PROCEDURE random_function |
---|
63 | END INTERFACE random_function |
---|
64 | |
---|
65 | CONTAINS |
---|
66 | |
---|
67 | SUBROUTINE random_function_ini |
---|
68 | |
---|
69 | IMPLICIT NONE |
---|
70 | |
---|
71 | random_iv = 0 |
---|
72 | random_iy = 0 |
---|
73 | |
---|
74 | END SUBROUTINE random_function_ini |
---|
75 | |
---|
76 | FUNCTION random_function( idum ) |
---|
77 | |
---|
78 | |
---|
79 | IMPLICIT NONE |
---|
80 | |
---|
81 | INTEGER :: ia, idum, im, iq, ir, ndiv, ntab |
---|
82 | REAL :: am, eps, random_function, rnmx |
---|
83 | |
---|
84 | PARAMETER ( ia=16807, im=2147483647, am=1.0/im, iq=127773, ir=2836, & |
---|
85 | ntab=32, ndiv=1+(im-1)/ntab, eps=1.2e-7, rnmx=1.0-eps ) |
---|
86 | |
---|
87 | INTEGER :: j, k |
---|
88 | |
---|
89 | |
---|
90 | IF ( idum .le. 0 .or. random_iy .eq. 0 ) THEN |
---|
91 | idum = max (-idum,1) |
---|
92 | DO j = ntab+8,1,-1 |
---|
93 | k = idum / iq |
---|
94 | idum = ia * ( idum - k * iq ) - ir * k |
---|
95 | IF ( idum .lt. 0 ) idum = idum + im |
---|
96 | IF ( j .le. ntab ) random_iv(j) = idum |
---|
97 | ENDDO |
---|
98 | random_iy = random_iv(1) |
---|
99 | ENDIF |
---|
100 | |
---|
101 | k = idum / iq |
---|
102 | idum = ia * ( idum - k * iq ) - ir * k |
---|
103 | IF ( idum .lt. 0 ) idum = idum + im |
---|
104 | j = 1 + random_iy / ndiv |
---|
105 | random_iy = random_iv(j) |
---|
106 | random_iv(j) = idum |
---|
107 | random_function = min ( am * random_iy , rnmx ) |
---|
108 | |
---|
109 | END FUNCTION random_function |
---|
110 | |
---|
111 | END MODULE random_function_mod |
---|