1 | FUNCTION random_gauss( idum, upper_limit ) |
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2 | |
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3 | !--------------------------------------------------------------------------------! |
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4 | ! This file is part of PALM. |
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5 | ! |
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6 | ! PALM is free software: you can redistribute it and/or modify it under the terms |
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7 | ! of the GNU General Public License as published by the Free Software Foundation, |
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8 | ! either version 3 of the License, or (at your option) any later version. |
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9 | ! |
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10 | ! PALM is distributed in the hope that it will be useful, but WITHOUT ANY |
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11 | ! WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR |
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12 | ! A PARTICULAR PURPOSE. See the GNU General Public License for more details. |
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13 | ! |
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14 | ! You should have received a copy of the GNU General Public License along with |
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15 | ! PALM. If not, see <http://www.gnu.org/licenses/>. |
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16 | ! |
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17 | ! Copyright 1997-2012 Leibniz University Hannover |
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18 | !--------------------------------------------------------------------------------! |
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19 | ! |
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20 | ! Current revisions: |
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21 | ! ----------------- |
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22 | ! |
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23 | ! |
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24 | ! Former revisions: |
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25 | ! ----------------- |
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26 | ! $Id: random_gauss.f90 1037 2012-10-22 14:10:22Z raasch $ |
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27 | ! |
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28 | ! 1036 2012-10-22 13:43:42Z raasch |
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29 | ! code put under GPL (PALM 3.9) |
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30 | ! |
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31 | ! RCS Log replace by Id keyword, revision history cleaned up |
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32 | ! |
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33 | ! Revision 1.4 2006/08/04 15:01:48 raasch |
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34 | ! Range of random number is limited by an upper limit (new second parameter) |
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35 | ! |
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36 | ! Revision 1.1 1998/03/25 20:09:47 raasch |
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37 | ! Initial revision |
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38 | ! |
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39 | ! |
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40 | ! Description: |
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41 | ! ------------ |
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42 | ! Generates a gaussian distributed random number (mean value 1, sigma = 1) |
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43 | ! This routine is taken from the "numerical recipies". |
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44 | !------------------------------------------------------------------------------! |
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45 | |
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46 | USE random_function_mod |
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47 | |
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48 | IMPLICIT NONE |
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49 | |
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50 | INTEGER :: idum, iset |
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51 | REAL :: fac, gset, random_gauss, rsq, upper_limit, v1, v2 |
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52 | |
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53 | SAVE iset, gset |
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54 | |
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55 | DATA iset /0/ |
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56 | |
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57 | ! |
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58 | !-- Random numbers are created as long as they do not fall below the given |
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59 | !-- upper limit |
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60 | DO |
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61 | |
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62 | IF ( iset == 0 ) THEN |
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63 | rsq = 0.0 |
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64 | DO WHILE ( rsq >= 1.0 .OR. rsq == 0.0 ) |
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65 | v1 = 2.0 * random_function( idum ) - 1.0 |
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66 | v2 = 2.0 * random_function( idum ) - 1.0 |
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67 | rsq = v1**2 + v2**2 |
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68 | ENDDO |
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69 | fac = SQRT( -2.0 * LOG( rsq ) / rsq ) |
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70 | gset = v1 * fac |
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71 | random_gauss = v2 * fac + 1.0 |
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72 | iset = 1 |
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73 | ELSE |
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74 | random_gauss = gset + 1.0 |
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75 | iset = 0 |
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76 | ENDIF |
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77 | |
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78 | IF ( ABS( random_gauss - 1.0 ) <= upper_limit ) EXIT |
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79 | |
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80 | ENDDO |
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81 | |
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82 | END FUNCTION random_gauss |
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