Gabriele Cosmo
204 lines
4.9 KiB
C++
204 lines
4.9 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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// $Id$
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//
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//
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// -------------------------------------------------------------------
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//
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// Class G4Pow
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//
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// Class description:
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//
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// Utility singleton class for the fast computation of log and pow
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// functions. Integer argument should in the interval 0-512, no
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// check is performed inside these methods for performance reasons.
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// For factorial integer argument should be in the interval 0-170
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// Computations with double arguments are fast for the interval
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// 0.5-255.5, standard library is used in the opposite case
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// Author: Vladimir Ivanchenko
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//
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// Creation date: 23.05.2009
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// -------------------------------------------------------------------
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#ifndef G4Pow_h
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#define G4Pow_h 1
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#include "globals.hh"
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#include "G4DataVector.hh"
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class G4Pow
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{
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public:
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static G4Pow* GetInstance();
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// Fast computation of Z^1/3
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//
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inline G4double Z13(G4int Z);
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inline G4double A13(G4double A);
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// Fast computation of Z^2/3
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//
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inline G4double Z23(G4int Z);
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inline G4double A23(G4double A);
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// Fast computation of log(Z)
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//
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inline G4double logZ(G4int Z);
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inline G4double logA(G4double A);
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// Fast computation of log10(Z)
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//
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inline G4double log10Z(G4int Z);
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inline G4double log10A(G4double A);
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// Fast computation of pow(Z,X)
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//
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inline G4double powZ(G4int Z, G4double y);
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inline G4double powA(G4double A, G4double y);
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G4double powN(G4double x, G4int n);
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// Fast factorial
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//
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inline G4double factorial(G4int Z);
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inline G4double logfactorial(G4int Z);
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private:
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G4Pow();
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~G4Pow();
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private:
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static G4Pow* fInstance;
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G4double onethird;
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G4DataVector pz13;
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G4DataVector lz;
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G4DataVector fact;
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G4DataVector logfact;
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};
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// -------------------------------------------------------------------
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inline G4double G4Pow::Z13(G4int Z)
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{
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return pz13[Z];
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}
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inline G4double G4Pow::A13(G4double A)
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{
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const G4double minA = 0.5000001;
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const G4double maxA = 255.5;
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G4double res;
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if((A >= minA) && (A <= maxA))
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{
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G4int i = G4int(A + 0.5);
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G4double x = (1.0 - A/G4double(i))*onethird;
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res = pz13[i]*(1.0 + x - x*x*(1.0 - 1.66666666*x));
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}
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else
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{
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res = std::pow(A, onethird);
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}
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return res;
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}
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inline G4double G4Pow::Z23(G4int Z)
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{
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G4double x = Z13(Z);
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return x*x;
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}
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inline G4double G4Pow::A23(G4double A)
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{
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G4double x = A13(A);
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return x*x;
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}
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inline G4double G4Pow::logZ(G4int Z)
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{
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return lz[Z];
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}
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inline G4double G4Pow::logA(G4double A)
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{
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const G4double minA = 0.5000001;
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const G4double maxA = 255.5;
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G4double res;
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if((A >= minA) && (A <= maxA))
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{
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G4int i = G4int(A + 0.5);
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G4double x = 1.0 - A/G4double(i);
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res = lz[i] + x*(1.0 - 0.5*x + onethird*x*x);
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}
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else
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{
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res = std::log(A);
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}
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return res;
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}
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inline G4double G4Pow::log10Z(G4int Z)
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{
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return lz[Z]/lz[10];
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}
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inline G4double G4Pow::log10A(G4double A)
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{
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return logA(A)/lz[10];
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}
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inline G4double G4Pow::powZ(G4int Z, G4double y)
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{
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return std::exp(y*lz[Z]);
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}
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inline G4double G4Pow::powA(G4double A, G4double y)
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{
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return std::exp(y*logA(A));
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}
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inline G4double G4Pow::factorial(G4int Z)
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{
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return fact[Z];
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}
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inline G4double G4Pow::logfactorial(G4int Z)
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{
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return logfact[Z];
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}
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// -------------------------------------------------------------------
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#endif
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