source: palm/trunk/SOURCE/random_gauss.f90 @ 1321

Last change on this file since 1321 was 1321, checked in by raasch, 7 years ago

last commit documented

  • Property svn:keywords set to Id
File size: 3.0 KB
Line 
1 FUNCTION random_gauss( idum, upper_limit )
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 1997-2014 Leibniz Universitaet Hannover
18!--------------------------------------------------------------------------------!
19!
20! Current revisions:
21! -----------------
22!
23!
24! Former revisions:
25! -----------------
26! $Id: random_gauss.f90 1321 2014-03-20 09:40:40Z raasch $
27!
28! 1320 2014-03-20 08:40:49Z raasch
29! ONLY-attribute added to USE-statements,
30! kind-parameters added to all INTEGER and REAL declaration statements,
31! kinds are defined in new module kinds,
32! old module precision_kind is removed,
33! revision history before 2012 removed,
34! comment fields (!:) to be used for variable explanations added to
35! all variable declaration statements
36!
37! 1036 2012-10-22 13:43:42Z raasch
38! code put under GPL (PALM 3.9)
39!
40! RCS Log replace by Id keyword, revision history cleaned up
41!
42! Revision 1.1  1998/03/25 20:09:47  raasch
43! Initial revision
44!
45!
46! Description:
47! ------------
48! Generates a gaussian distributed random number (mean value 1, sigma = 1)
49! This routine is taken from the "numerical recipies".
50!------------------------------------------------------------------------------!
51
52    USE kinds
53
54    USE random_function_mod,                                                   &
55        ONLY:  random_function
56
57    IMPLICIT NONE
58
59    INTEGER(iwp) ::  idum          !:
60    INTEGER(iwp) ::  iset          !:
61
62    REAL(wp)     ::  fac           !:
63    REAL(wp)     ::  gset          !:
64    REAL(wp)     ::  random_gauss  !:
65    REAL(wp)     ::  rsq           !:
66    REAL(wp)     ::  upper_limit   !:
67    REAL(wp)     ::  v1            !:
68    REAL(wp)     ::  v2            !:
69
70    SAVE  iset, gset
71
72    DATA  iset /0/
73
74!
75!-- Random numbers are created as long as they do not fall below the given
76!-- upper limit
77    DO
78
79       IF ( iset == 0 )  THEN
80          rsq = 0.0
81          DO  WHILE ( rsq >= 1.0  .OR.  rsq == 0.0 )
82             v1  = 2.0 * random_function( idum ) - 1.0
83             v2  = 2.0 * random_function( idum ) - 1.0
84             rsq = v1**2 + v2**2
85          ENDDO
86          fac          = SQRT( -2.0 * LOG( rsq ) / rsq )
87          gset         = v1 * fac
88          random_gauss = v2 * fac + 1.0
89          iset         = 1
90       ELSE
91          random_gauss = gset + 1.0
92          iset         = 0
93       ENDIF
94
95       IF ( ABS( random_gauss - 1.0 ) <= upper_limit )  EXIT
96
97    ENDDO
98
99 END FUNCTION random_gauss
Note: See TracBrowser for help on using the repository browser.