source: palm/trunk/SOURCE/random_function.f90 @ 1093

Last change on this file since 1093 was 1093, checked in by raasch, 8 years ago

last commit documented

  • Property svn:keywords set to Id
File size: 3.1 KB
Line 
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 raasch $
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
Note: See TracBrowser for help on using the repository browser.