Gabriele Cosmo
122 lines
4.2 KiB
C++
122 lines
4.2 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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// G4GaussHermiteQ class implementation
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//
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// Author: V.Grichine, 13.05.1997 V.Grichine
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// --------------------------------------------------------------------
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#include "G4GaussHermiteQ.hh"
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#include "G4PhysicalConstants.hh"
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// ----------------------------------------------------------
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//
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// Constructor for Gauss-Hermite
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G4GaussHermiteQ::G4GaussHermiteQ(function pFunction, G4int nHermite)
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: G4VGaussianQuadrature(pFunction)
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{
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const G4double tolerance = 1.0e-12;
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const G4int maxNumber = 12;
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G4int i = 1, j = 1, k = 1;
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G4double newton0 = 0.;
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G4double newton1 = 0.0, temp1 = 0.0, temp2 = 0.0, temp3 = 0.0, temp = 0.0;
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G4double piInMinusQ = std::pow(pi, -0.25); // 1.0/std::sqrt(std::sqrt(pi)) ??
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fNumber = (nHermite + 1) / 2;
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fAbscissa = new G4double[fNumber];
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fWeight = new G4double[fNumber];
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for(i = 1; i <= fNumber; ++i)
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{
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if(i == 1)
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{
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newton0 =
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std::sqrt((G4double)(2 * nHermite + 1)) -
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1.85575001 * std::pow((G4double)(2 * nHermite + 1), -0.16666999);
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}
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else if(i == 2)
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{
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newton0 -= 1.14001 * std::pow((G4double) nHermite, 0.425999) / newton0;
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}
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else if(i == 3)
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{
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newton0 = 1.86002 * newton0 - 0.86002 * fAbscissa[0];
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}
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else if(i == 4)
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{
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newton0 = 1.91001 * newton0 - 0.91001 * fAbscissa[1];
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}
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else
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{
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newton0 = 2.0 * newton0 - fAbscissa[i - 3];
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}
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for(k = 1; k <= maxNumber; ++k)
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{
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temp1 = piInMinusQ;
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temp2 = 0.0;
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for(j = 1; j <= nHermite; ++j)
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{
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temp3 = temp2;
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temp2 = temp1;
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temp1 = newton0 * std::sqrt(2.0 / j) * temp2 -
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std::sqrt(((G4double)(j - 1)) / j) * temp3;
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}
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temp = std::sqrt((G4double) 2 * nHermite) * temp2;
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newton1 = newton0;
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newton0 = newton1 - temp1 / temp;
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if(std::fabs(newton0 - newton1) <= tolerance)
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{
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break;
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}
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}
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if(k > maxNumber)
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{
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G4Exception("G4GaussHermiteQ::G4GaussHermiteQ()", "OutOfRange",
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FatalException,
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"Too many iterations in Gauss-Hermite constructor.");
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}
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fAbscissa[i - 1] = newton0;
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fWeight[i - 1] = 2.0 / (temp * temp);
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}
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}
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// ----------------------------------------------------------
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//
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// Gauss-Hermite method for integration of std::exp(-x*x)*nFunction(x)
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// from minus infinity to plus infinity .
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G4double G4GaussHermiteQ::Integral() const
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{
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G4double integral = 0.0;
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for(G4int i = 0; i < fNumber; ++i)
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{
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integral +=
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fWeight[i] * (fFunction(fAbscissa[i]) + fFunction(-fAbscissa[i]));
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}
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return integral;
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}
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