1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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4 | // * * |
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5 | // * The Geant4 software is copyright of the Copyright Holders of * |
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6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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7 | // * conditions of the Geant4 Software License, included in the file * |
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8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
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9 | // * include a list of copyright holders. * |
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10 | // * * |
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11 | // * Neither the authors of this software system, nor their employing * |
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12 | // * institutes,nor the agencies providing financial support for this * |
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13 | // * work make any representation or warranty, express or implied, * |
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14 | // * regarding this software system or assume any liability for its * |
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15 | // * use. Please see the license in the file LICENSE and URL above * |
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16 | // * for the full disclaimer and the limitation of liability. * |
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17 | // * * |
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18 | // * This code implementation is the result of the scientific and * |
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19 | // * technical work of the GEANT4 collaboration. * |
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20 | // * By using, copying, modifying or distributing the software (or * |
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21 | // * any work based on the software) you agree to acknowledge its * |
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22 | // * use in resulting scientific publications, and indicate your * |
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23 | // * acceptance of all terms of the Geant4 Software license. * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // $Id: G4Pow.hh,v 1.7 2010/08/24 08:12:08 gcosmo Exp $ |
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27 | // GEANT4 tag $Name: global-V09-03-22 $ |
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28 | // |
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29 | // |
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30 | // ------------------------------------------------------------------- |
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31 | // |
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32 | // Class G4Pow |
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33 | // |
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34 | // Class description: |
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35 | // |
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36 | // Utility singleton class for the fast computation of log and pow |
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37 | // functions. Integer argument should in the interval 0-255, no |
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38 | // check is performed inside these methods for performance reasons. |
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39 | // Computations with double arguments are fast for the interval |
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40 | // 0.5-255.5, standard library is used in the opposite case |
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41 | |
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42 | // Author: Vladimir Ivanchenko |
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43 | // |
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44 | // Creation date: 23.05.2009 |
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45 | // ------------------------------------------------------------------- |
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46 | |
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47 | #ifndef G4Pow_h |
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48 | #define G4Pow_h 1 |
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49 | |
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50 | #include "globals.hh" |
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51 | #include "G4DataVector.hh" |
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52 | |
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53 | class G4Pow |
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54 | { |
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55 | |
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56 | public: |
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57 | |
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58 | static G4Pow* GetInstance(); |
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59 | |
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60 | // Fast computation of Z^1/3 |
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61 | // |
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62 | inline G4double Z13(G4int Z); |
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63 | inline G4double A13(G4double A); |
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64 | |
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65 | // Fast computation of Z^2/3 |
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66 | // |
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67 | inline G4double Z23(G4int Z); |
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68 | inline G4double A23(G4double A); |
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69 | |
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70 | // Fast computation of log(Z) |
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71 | // |
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72 | inline G4double logZ(G4int Z); |
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73 | inline G4double logA(G4double A); |
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74 | |
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75 | // Fast computation of log10(Z) |
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76 | // |
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77 | inline G4double log10Z(G4int Z); |
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78 | inline G4double log10A(G4double A); |
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79 | |
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80 | // Fast computation of pow(Z,X) |
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81 | // |
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82 | inline G4double powZ(G4int Z, G4double y); |
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83 | inline G4double powA(G4double A, G4double y); |
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84 | G4double powN(G4double x, G4int n); |
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85 | |
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86 | // Fast factorial |
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87 | // |
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88 | inline G4double factorial(G4int Z); |
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89 | inline G4double logfactorial(G4int Z); |
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90 | |
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91 | private: |
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92 | |
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93 | G4Pow(); |
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94 | ~G4Pow(); |
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95 | |
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96 | private: |
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97 | |
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98 | static G4Pow* fInstance; |
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99 | |
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100 | G4double onethird; |
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101 | |
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102 | G4DataVector pz13; |
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103 | G4DataVector lz; |
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104 | G4DataVector fact; |
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105 | G4DataVector logfact; |
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106 | }; |
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107 | |
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108 | // ------------------------------------------------------------------- |
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109 | |
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110 | inline G4double G4Pow::Z13(G4int Z) |
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111 | { |
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112 | return pz13[Z]; |
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113 | } |
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114 | |
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115 | inline G4double G4Pow::A13(G4double A) |
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116 | { |
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117 | const G4double minA = 0.5000001; |
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118 | const G4double maxA = 255.5; |
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119 | |
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120 | G4double res; |
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121 | if((A >= minA) && (A <= maxA)) |
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122 | { |
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123 | G4int i = G4int(A + 0.5); |
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124 | G4double x = (1.0 - A/G4double(i))*onethird; |
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125 | res = pz13[i]*(1.0 + x - x*x*(1.0 - 1.66666666*x)); |
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126 | } |
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127 | else |
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128 | { |
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129 | res = std::pow(A, onethird); |
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130 | } |
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131 | return res; |
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132 | } |
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133 | |
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134 | inline G4double G4Pow::Z23(G4int Z) |
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135 | { |
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136 | G4double x = Z13(Z); |
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137 | return x*x; |
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138 | } |
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139 | |
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140 | inline G4double G4Pow::A23(G4double A) |
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141 | { |
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142 | G4double x = A13(A); |
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143 | return x*x; |
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144 | } |
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145 | |
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146 | inline G4double G4Pow::logZ(G4int Z) |
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147 | { |
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148 | return lz[Z]; |
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149 | } |
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150 | |
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151 | inline G4double G4Pow::logA(G4double A) |
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152 | { |
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153 | const G4double minA = 0.5000001; |
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154 | const G4double maxA = 255.5; |
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155 | |
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156 | G4double res; |
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157 | if((A >= minA) && (A <= maxA)) |
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158 | { |
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159 | G4int i = G4int(A + 0.5); |
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160 | G4double x = 1.0 - A/G4double(i); |
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161 | res = lz[i] + x*(1.0 - 0.5*x + onethird*x*x); |
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162 | } |
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163 | else |
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164 | { |
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165 | res = std::log(A); |
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166 | } |
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167 | return res; |
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168 | } |
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169 | |
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170 | inline G4double G4Pow::log10Z(G4int Z) |
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171 | { |
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172 | return lz[Z]/lz[10]; |
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173 | } |
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174 | |
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175 | inline G4double G4Pow::log10A(G4double A) |
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176 | { |
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177 | return logA(A)/lz[10]; |
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178 | } |
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179 | |
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180 | inline G4double G4Pow::powZ(G4int Z, G4double y) |
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181 | { |
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182 | return std::exp(y*lz[Z]); |
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183 | } |
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184 | |
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185 | inline G4double G4Pow::powA(G4double A, G4double y) |
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186 | { |
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187 | return std::exp(y*logA(A)); |
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188 | } |
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189 | |
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190 | inline G4double G4Pow::factorial(G4int Z) |
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191 | { |
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192 | return fact[Z]; |
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193 | } |
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194 | |
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195 | inline G4double G4Pow::logfactorial(G4int Z) |
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196 | { |
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197 | return logfact[Z]; |
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198 | } |
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199 | |
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200 | // ------------------------------------------------------------------- |
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201 | |
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202 | #endif |
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203 | |
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