1 | MODULE ran_num |
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2 | !!====================================================================== |
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3 | !! *** MODULE ran_num *** |
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4 | !! NEMOVAR: Random number routines |
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5 | !!====================================================================== |
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6 | !!---------------------------------------------------------------------- |
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7 | !! gaustb : returns a gaussian randum number with mean and std. |
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8 | !! gaustb_2d : returns a gaussian randum number with mean and std for a |
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9 | !! given horizontal grid point |
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10 | !!---------------------------------------------------------------------- |
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11 | !! * Modules used |
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12 | USE par_kind ! Kind variables |
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13 | USE dom_oce ! Domain variables |
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14 | USE in_out_manager ! I/O stuff |
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15 | USE mt19937ar, ONLY : & |
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16 | & init_mtrand, & |
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17 | & mtrand_real1 |
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18 | |
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19 | IMPLICIT NONE |
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20 | |
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21 | !! * Routine accessibility |
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22 | |
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23 | PRIVATE |
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24 | |
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25 | PUBLIC & |
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26 | & gaustb, & |
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27 | & gaustb_2d |
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28 | |
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29 | CONTAINS |
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30 | |
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31 | FUNCTION gaustb( pamp, pmean ) |
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32 | !!---------------------------------------------------------------------- |
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33 | !! *** ROUTINE gaustb *** |
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34 | !! |
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35 | !! ** Purpose : Returns a gaussian randum number with mean and std. |
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36 | !! |
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37 | !! ** Method : Generate Gaussian random variables. |
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38 | !! The standard deviation and mean of the variables are |
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39 | !! specified by the variables pamp and pmean. |
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40 | !! |
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41 | !! ** Action : |
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42 | !! |
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43 | !! History : |
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44 | !! ! 07-07 (K. Mogensen) Original code based on gaustb.F |
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45 | !!---------------------------------------------------------------------- |
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46 | !! * Function return |
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47 | REAL(wp) :: & |
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48 | & gaustb |
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49 | !! * Arguments |
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50 | REAL(wp), INTENT(IN) :: & |
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51 | & pamp, & ! Amplitude |
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52 | & pmean ! Mean value |
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53 | !! * Local declarations |
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54 | |
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55 | gaustb = pamp * gausva( ) + pmean |
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56 | |
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57 | END FUNCTION gaustb |
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58 | |
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59 | |
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60 | FUNCTION gausva( ) |
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61 | !!---------------------------------------------------------------------- |
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62 | !! *** ROUTINE gausva *** |
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63 | !! |
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64 | !! ** Purpose : Returns a normally distributed deviate with 0 mean |
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65 | !! and unit variance using the unifva(kdum) as the |
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66 | !! source of uniform deviates. |
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67 | !! |
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68 | !! ** Method : |
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69 | !! |
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70 | !! ** Action : |
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71 | !! |
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72 | !! History : |
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73 | !! ! 07-07 (K. Mogensen) Original code based on gaustb.F |
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74 | !!---------------------------------------------------------------------- |
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75 | !! * Function return |
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76 | REAL(wp) :: & |
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77 | & gausva |
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78 | !! * Local declarations |
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79 | REAL(wp), SAVE :: & |
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80 | & gset |
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81 | INTEGER, SAVE :: & |
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82 | & niset = 0 |
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83 | REAL(wp) :: & |
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84 | & zfac, & |
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85 | & zrsq, & |
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86 | & zv1, & |
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87 | & zv2 |
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88 | |
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89 | ! Begin main |
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90 | |
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91 | IF ( niset == 0 ) THEN |
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92 | |
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93 | zv1 = 2.0_wp * psrandom( ) - 1.0_wp |
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94 | zv2 = 2.0_wp * psrandom( ) - 1.0_wp |
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95 | zrsq = zv1**2 + zv2**2 |
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96 | |
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97 | DO WHILE ( ( zrsq >= 1.0_wp ) .OR. ( zrsq == 0.0_wp ) ) |
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98 | |
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99 | zv1 = 2.0_wp * psrandom( ) - 1.0_wp |
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100 | zv2 = 2.0_wp * psrandom( ) - 1.0_wp |
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101 | zrsq = zv1**2 + zv2**2 |
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102 | |
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103 | END DO |
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104 | |
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105 | zfac = SQRT( -2.0_wp * LOG( zrsq ) / zrsq ) |
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106 | gset = zv1 * zfac |
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107 | gausva = zv2 * zfac |
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108 | niset = 1 |
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109 | |
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110 | ELSE |
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111 | |
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112 | gausva = gset |
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113 | niset = 0 |
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114 | |
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115 | ENDIF |
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116 | |
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117 | END FUNCTION gausva |
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118 | |
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119 | FUNCTION gaustb_2d( ki, kj, pamp, pmean ) |
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120 | !!---------------------------------------------------------------------- |
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121 | !! *** ROUTINE gaustb_2d *** |
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122 | !! |
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123 | !! ** Purpose : Returns a Gaussian randum number with mean and std |
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124 | !! for a given horizontal grid point. |
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125 | !! |
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126 | !! ** Method : Generate Gaussian random variables. |
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127 | !! The standard deviation and mean of the variables are |
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128 | !! specified by the variables pamp and pmean. |
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129 | !! |
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130 | !! ** Action : |
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131 | !! |
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132 | !! History : |
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133 | !! ! 07-07 (K. Mogensen) Original code based on gaustb.F |
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134 | !!---------------------------------------------------------------------- |
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135 | !! * Function return |
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136 | REAL(wp) :: & |
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137 | & gaustb_2d |
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138 | !! * Arguments |
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139 | INTEGER, INTENT(IN) :: & |
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140 | & ki, & ! Indices in seed array |
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141 | & kj |
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142 | REAL(wp), INTENT(IN) :: & |
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143 | & pamp, & ! Amplitude |
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144 | & pmean ! Mean value |
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145 | !! * Local declarations |
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146 | |
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147 | gaustb_2d = pamp * gausva_2d( ki, kj ) + pmean |
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148 | |
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149 | END FUNCTION gaustb_2d |
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150 | |
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151 | FUNCTION gausva_2d( ki, kj ) |
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152 | !!---------------------------------------------------------------------- |
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153 | !! *** ROUTINE gausva_2d *** |
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154 | !! |
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155 | !! ** Purpose : Returns a normally distributed deviate with 0 mean |
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156 | !! and unit variance. |
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157 | !! |
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158 | !! ** Method : |
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159 | !! |
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160 | !! ** Action : |
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161 | !! |
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162 | !! History : |
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163 | !! ! 07-07 (K. Mogensen) Original code based on gaustb.F |
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164 | !!---------------------------------------------------------------------- |
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165 | !! * Function return |
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166 | REAL(wp) :: & |
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167 | & gausva_2d |
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168 | !! * Arguments |
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169 | INTEGER, INTENT(IN) :: & |
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170 | & ki, & ! Indices in seed array |
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171 | & kj |
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172 | !! * Local declarations |
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173 | REAL(wp), DIMENSION(jpi,jpj) :: & |
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174 | & gset |
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175 | INTEGER, DIMENSION(jpi,jpj) :: & |
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176 | & niset |
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177 | LOGICAL, SAVE :: & |
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178 | & llinit = .FALSE. |
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179 | REAL(wp) :: & |
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180 | & zfac, & |
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181 | & zrsq, & |
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182 | & zv1, & |
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183 | & zv2 |
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184 | |
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185 | ! Initialization |
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186 | |
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187 | IF ( .NOT. llinit ) THEN |
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188 | |
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189 | niset(:,:) = 0 |
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190 | llinit = .TRUE. |
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191 | |
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192 | ENDIF |
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193 | |
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194 | ! Begin main |
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195 | |
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196 | IF ( niset(ki,kj) == 0 ) THEN |
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197 | |
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198 | zv1 = 2.0_wp * psrandom( ) - 1.0_wp |
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199 | zv2 = 2.0_wp * psrandom( ) - 1.0_wp |
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200 | zrsq = zv1**2 + zv2**2 |
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201 | |
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202 | DO WHILE ( ( zrsq >= 1.0_wp ) .OR. ( zrsq == 0.0_wp ) ) |
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203 | |
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204 | zv1 = 2.0_wp * psrandom( ) - 1.0_wp |
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205 | zv2 = 2.0_wp * psrandom( ) - 1.0_wp |
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206 | zrsq = zv1**2 + zv2**2 |
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207 | |
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208 | END DO |
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209 | |
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210 | zfac = SQRT( -2.0_wp * LOG( zrsq ) / zrsq ) |
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211 | gset(ki,kj) = zv1 * zfac |
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212 | gausva_2d = zv2 * zfac |
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213 | niset(ki,kj) = 1 |
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214 | |
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215 | ELSE |
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216 | |
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217 | gausva_2d = gset(ki,kj) |
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218 | niset(ki,kj) = 0 |
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219 | |
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220 | ENDIF |
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221 | |
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222 | END FUNCTION gausva_2d |
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223 | |
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224 | FUNCTION psrandom() |
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225 | !!---------------------------------------------------------------------- |
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226 | !! *** ROUTINE psrandom *** |
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227 | !! |
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228 | !! ** Purpose : Pseudo-Random number generator. |
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229 | !! |
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230 | !! ** Method : Returns a pseudo-random number from a uniform distribution |
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231 | !! between 0 and 1 |
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232 | !! Call with kdum a negative integer to initialize. |
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233 | !! Thereafter, do not alter kdum between successive deviates |
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234 | !! in sequence. |
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235 | !! |
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236 | !! ** Action : |
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237 | !! |
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238 | !! History : |
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239 | !! ! 10-02 (F. Vigilant) Original code |
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240 | !! ! 2011-08 (D. Lea) initialize with kdum1 |
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241 | !!---------------------------------------------------------------------- |
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242 | !! * Function return |
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243 | REAL(wp) :: & |
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244 | & psrandom |
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245 | !! * Arguments |
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246 | INTEGER :: & |
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247 | & kdum ! Seed |
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248 | LOGICAL, SAVE :: & |
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249 | & llinit = .TRUE. ! Initialize on first call |
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250 | |
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251 | ! Initialization |
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252 | IF ( llinit ) THEN |
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253 | kdum = 456953 + nproc * 596035 |
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254 | CALL init_mtrand(kdum) |
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255 | llinit = .FALSE. ! On subsequent calls do not reinitialize |
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256 | ENDIF |
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257 | |
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258 | psrandom = mtrand_real1() |
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259 | |
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260 | END FUNCTION psrandom |
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261 | |
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262 | |
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263 | END MODULE ran_num |
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