G4Pow.hh

Go to the documentation of this file.
00001 //
00002 // ********************************************************************
00003 // * License and Disclaimer                                           *
00004 // *                                                                  *
00005 // * The  Geant4 software  is  copyright of the Copyright Holders  of *
00006 // * the Geant4 Collaboration.  It is provided  under  the terms  and *
00007 // * conditions of the Geant4 Software License,  included in the file *
00008 // * LICENSE and available at  http://cern.ch/geant4/license .  These *
00009 // * include a list of copyright holders.                             *
00010 // *                                                                  *
00011 // * Neither the authors of this software system, nor their employing *
00012 // * institutes,nor the agencies providing financial support for this *
00013 // * work  make  any representation or  warranty, express or implied, *
00014 // * regarding  this  software system or assume any liability for its *
00015 // * use.  Please see the license in the file  LICENSE  and URL above *
00016 // * for the full disclaimer and the limitation of liability.         *
00017 // *                                                                  *
00018 // * This  code  implementation is the result of  the  scientific and *
00019 // * technical work of the GEANT4 collaboration.                      *
00020 // * By using,  copying,  modifying or  distributing the software (or *
00021 // * any work based  on the software)  you  agree  to acknowledge its *
00022 // * use  in  resulting  scientific  publications,  and indicate your *
00023 // * acceptance of all terms of the Geant4 Software license.          *
00024 // ********************************************************************
00025 //
00026 // $Id: G4Pow.hh 69386 2013-05-02 10:35:42Z vnivanch $
00027 //
00028 //
00029 // -------------------------------------------------------------------
00030 //
00031 // Class G4Pow
00032 //
00033 // Class description:
00034 //
00035 // Utility singleton class for the fast computation of log and pow
00036 // functions. Integer argument should in the interval 0-512, no
00037 // check is performed inside these methods for performance reasons.
00038 // For factorial integer argument should be in the interval 0-170
00039 // Computations with double arguments are fast for the interval
00040 // 0.5-255.5, standard library is used in the opposite case
00041 
00042 // Author: Vladimir Ivanchenko
00043 //
00044 // Creation date: 23.05.2009
00045 // -------------------------------------------------------------------
00046 
00047 #ifndef G4Pow_h
00048 #define G4Pow_h 1
00049 
00050 #include "globals.hh"
00051 #include "G4DataVector.hh"
00052 
00053 class G4Pow
00054 {
00055 
00056   public:
00057 
00058     static G4Pow* GetInstance();
00059 
00060     // Fast computation of Z^1/3
00061     //
00062     inline G4double Z13(G4int Z);
00063     inline G4double A13(G4double A);
00064 
00065     // Fast computation of Z^2/3
00066     //
00067     inline G4double Z23(G4int Z);
00068     inline G4double A23(G4double A);
00069 
00070     // Fast computation of log(Z)
00071     //
00072     inline G4double logZ(G4int Z);
00073     inline G4double logA(G4double A);
00074 
00075     // Fast computation of log10(Z)
00076     //
00077     inline G4double log10Z(G4int Z);
00078     inline G4double log10A(G4double A);
00079 
00080     // Fast computation of pow(Z,X)
00081     //
00082     inline G4double powZ(G4int Z, G4double y);
00083     inline G4double powA(G4double A, G4double y);
00084            G4double powN(G4double x, G4int n);
00085 
00086     // Fast factorial
00087     //
00088     inline G4double factorial(G4int Z);
00089     inline G4double logfactorial(G4int Z);
00090 
00091   private:
00092 
00093     G4Pow();
00094    ~G4Pow();
00095 
00096   private:
00097 
00098     static G4Pow* fpInstance;
00099 
00100     const G4double onethird;
00101     const G4double minA;
00102     const G4double maxA;
00103 
00104     G4DataVector pz13;
00105     G4DataVector lz;
00106     G4DataVector fact;
00107     G4DataVector logfact;
00108 };
00109 
00110 // -------------------------------------------------------------------
00111 
00112 inline G4double G4Pow::Z13(G4int Z)
00113 {
00114   return pz13[Z];
00115 }
00116 
00117 inline G4double G4Pow::A13(G4double A)
00118 {
00119   G4double res;
00120   G4double a = A;
00121   if(1.0 > A) { a = 1.0/A; }
00122   if(a <= maxA)
00123   {
00124     G4int i = G4int(a + 0.5);
00125     G4double x = (a/G4double(i) - 1.0)*onethird;
00126     res = pz13[i]*(1.0 + x - x*x*(1.0 - 1.66666666*x));
00127     if(1.0 > A) { res = 1.0/res; }
00128   }
00129   else
00130   {
00131     res = std::pow(A, onethird); 
00132   }
00133   return res;
00134 }
00135 
00136 inline G4double G4Pow::Z23(G4int Z)
00137 {
00138   G4double x = Z13(Z);
00139   return x*x;
00140 }
00141 
00142 inline G4double G4Pow::A23(G4double A)
00143 {
00144   G4double x = A13(A);
00145   return x*x;
00146 }
00147 
00148 inline G4double G4Pow::logZ(G4int Z)
00149 {
00150   return lz[Z];
00151 }
00152 
00153 inline G4double G4Pow::logA(G4double A)
00154 {
00155   G4double res;
00156   G4double a = A;
00157   if(1.0 > A) { a = 1.0/A; }
00158   if(a <= maxA)
00159   {
00160     G4int i = G4int(a + 0.5);
00161     G4double x = a/G4double(i) - 1;
00162     res = lz[i] + x*(1.0 - (0.5 - onethird*x)*x);
00163     if(1.0 > A) { res = -res; }
00164   }
00165   else
00166   {
00167     res = std::log(A);
00168   }
00169   return res;
00170 }
00171 
00172 inline G4double G4Pow::log10Z(G4int Z)
00173 {
00174   return lz[Z]/lz[10];
00175 }
00176 
00177 inline G4double G4Pow::log10A(G4double A)
00178 {
00179   return logA(A)/lz[10];
00180 }
00181 
00182 inline G4double G4Pow::powZ(G4int Z, G4double y)
00183 {
00184   return std::exp(y*lz[Z]);
00185 }
00186 
00187 inline G4double G4Pow::powA(G4double A, G4double y)
00188 {
00189   return std::exp(y*logA(A));
00190 }
00191 
00192 inline G4double G4Pow::factorial(G4int Z)
00193 {
00194   return fact[Z];
00195 }
00196 
00197 inline G4double G4Pow::logfactorial(G4int Z)
00198 {
00199   return logfact[Z];
00200 }
00201 
00202 // -------------------------------------------------------------------
00203 
00204 #endif
00205 

Generated on Mon May 27 17:49:24 2013 for Geant4 by  doxygen 1.4.7