Gabriele Cosmo
277 lines
6.5 KiB
C++
277 lines
6.5 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: G4Pow.hh 93311 2015-10-16 10:16:37Z gcosmo $
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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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// 0.002-511.5 for all functions except exponent, which is computed
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// for the interval 0-84.4, 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 "G4Log.hh"
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#include "G4Exp.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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~G4Pow();
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// Fast computation of Z^1/3
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//
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inline G4double Z13(G4int Z) const;
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inline G4double A13(G4double A) const;
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// Fast computation of Z^2/3
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//
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inline G4double Z23(G4int Z) const;
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inline G4double A23(G4double A) const;
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// Fast computation of log(Z)
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//
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inline G4double logZ(G4int Z) const;
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inline G4double logA(G4double A) const;
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inline G4double logX(G4double x) const;
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// Fast computation of log10(Z)
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//
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inline G4double log10Z(G4int Z) const;
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inline G4double log10A(G4double A) const;
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// Fast computation of exp(X)
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//
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inline G4double expA(G4double A) const;
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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) const;
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inline G4double powA(G4double A, G4double y) const;
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G4double powN(G4double x, G4int n) const;
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// Fast factorial
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//
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inline G4double factorial(G4int Z) const;
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inline G4double logfactorial(G4int Z) const;
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private:
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G4Pow();
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inline G4double logBase(G4double x) const;
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static G4Pow* fpInstance;
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const G4double onethird;
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const G4int max2;
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G4double maxA;
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G4double maxA2;
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G4double maxAexp;
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G4DataVector ener;
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G4DataVector logen;
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G4DataVector pz13;
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G4DataVector lz;
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G4DataVector lz2;
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G4DataVector fexp;
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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) const
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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) const
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{
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G4double res = 0.0;
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if(A > 0.0)
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{
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G4double a = (1.0 <= A) ? A : 1.0/A;
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if(1.0 > A) { a = 1.0/A; }
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if(a <= maxA)
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{
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G4int i = G4int(a + 0.5);
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G4double x = (a/G4double(i) - 1.0)*onethird;
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res = pz13[i]*(1.0 + x - x*x*(1.0 - 1.66666666*x));
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if(1.0 > A) { res = 1.0/res; }
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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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}
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return res;
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}
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inline G4double G4Pow::Z23(G4int Z) const
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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) const
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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) const
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{
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return lz[Z];
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}
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inline G4double G4Pow::logBase(G4double a) const
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{
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G4double res;
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if(a <= maxA2)
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{
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G4int i = G4int(max2*(a - 1) + 0.5);
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if(i > max2) { i = max2; }
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G4double x = a/(G4double(i)/max2 + 1) - 1;
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res = lz2[i] + x*(1.0 - (0.5 - onethird*x)*x);
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}
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else if(a <= maxA)
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{
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G4int i = G4int(a + 0.5);
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G4double x = a/G4double(i) - 1;
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res = lz[i] + x*(1.0 - (0.5 - onethird*x)*x);
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}
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else
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{
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res = G4Log(a);
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}
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return res;
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}
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inline G4double G4Pow::logA(G4double A) const
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{
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return (1.0 <= A ? logBase(A) : -logBase(1./A));
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}
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inline G4double G4Pow::logX(G4double x) const
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{
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G4double res = 0.0;
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G4double a = (1.0 <= x) ? x : 1.0/x;
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if(a <= maxA)
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{
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res = logBase(a);
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}
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else if(a <= ener[2])
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{
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res = logen[1] + logBase(a/ener[1]);
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}
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else if(a <= ener[3])
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{
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res = logen[2] + logBase(a/ener[2]);
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}
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else
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{
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res = G4Log(a);
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}
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if(1.0 > x) { res = -res; }
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return res;
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}
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inline G4double G4Pow::log10Z(G4int Z) const
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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) const
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{
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return logX(A)/lz[10];
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}
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inline G4double G4Pow::expA(G4double A) const
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{
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G4double res;
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G4double a = (0.0 <= A) ? A : -A;
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if(a <= maxAexp)
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{
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G4int i = G4int(2*a + 0.5);
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G4double x = a - i*0.5;
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res = fexp[i]*(1.0 + x*(1.0 + 0.5*(1.0 + onethird*x)*x));
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}
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else
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{
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res = G4Exp(a);
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}
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if(0.0 > A) { res = 1.0/res; }
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return res;
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}
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inline G4double G4Pow::powZ(G4int Z, G4double y) const
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{
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return expA(y*lz[Z]);
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}
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inline G4double G4Pow::powA(G4double A, G4double y) const
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{
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return (0.0 == A ? 0.0 : expA(y*logX(A)));
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}
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inline G4double G4Pow::factorial(G4int Z) const
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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) const
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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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