Gabriele Cosmo
155 lines
5.3 KiB
C++
155 lines
5.3 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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// G4SimpleIntegration class implementation
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//
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// Author: V.Grichine, 26.03.1997
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// --------------------------------------------------------------------
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#include "G4SimpleIntegration.hh"
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#include "globals.hh"
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G4SimpleIntegration::G4SimpleIntegration(function pFunction)
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: fFunction(pFunction)
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{}
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G4SimpleIntegration::G4SimpleIntegration(function pFunction,
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G4double pTolerance)
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: fFunction(pFunction)
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, fTolerance(pTolerance)
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{}
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// Simple integration methods
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G4double G4SimpleIntegration::Trapezoidal(G4double xInitial, G4double xFinal,
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G4int iterationNumber)
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{
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G4double Step = (xFinal - xInitial) / iterationNumber;
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G4double mean = (fFunction(xInitial) + fFunction(xFinal)) * 0.5;
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G4double x = xInitial;
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for(G4int i = 1; i < iterationNumber; ++i)
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{
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x += Step;
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mean += fFunction(x);
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}
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return mean * Step;
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}
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G4double G4SimpleIntegration::MidPoint(G4double xInitial, G4double xFinal,
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G4int iterationNumber)
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{
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G4double Step = (xFinal - xInitial) / iterationNumber;
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G4double x = xInitial + 0.5 * Step;
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G4double mean = fFunction(x);
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for(G4int i = 1; i < iterationNumber; ++i)
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{
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x += Step;
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mean += fFunction(x);
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}
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return mean * Step;
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}
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G4double G4SimpleIntegration::Gauss(G4double xInitial, G4double xFinal,
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G4int iterationNumber)
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{
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G4double x = 0.;
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static const G4double root = 1.0 / std::sqrt(3.0);
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G4double Step = (xFinal - xInitial) / (2.0 * iterationNumber);
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G4double delta = Step * root;
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G4double mean = 0.0;
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for(G4int i = 0; i < iterationNumber; ++i)
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{
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x = (2 * i + 1) * Step;
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mean += (fFunction(x + delta) + fFunction(x - delta));
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}
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return mean * Step;
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}
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G4double G4SimpleIntegration::Simpson(G4double xInitial, G4double xFinal,
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G4int iterationNumber)
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{
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G4double Step = (xFinal - xInitial) / iterationNumber;
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G4double x = xInitial;
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G4double xPlus = xInitial + 0.5 * Step;
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G4double mean = (fFunction(xInitial) + fFunction(xFinal)) * 0.5;
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G4double sum = fFunction(xPlus);
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for(G4int i = 1; i < iterationNumber; ++i)
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{
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x += Step;
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xPlus += Step;
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mean += fFunction(x);
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sum += fFunction(xPlus);
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}
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mean += 2.0 * sum;
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return mean * Step / 3.0;
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}
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// Adaptive Gauss integration
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G4double G4SimpleIntegration::AdaptGaussIntegration(G4double xInitial,
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G4double xFinal)
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{
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G4int depth = 0;
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G4double sum = 0.0;
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AdaptGauss(xInitial, xFinal, sum, depth);
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return sum;
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}
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G4double G4SimpleIntegration::Gauss(G4double xInitial, G4double xFinal)
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{
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static const G4double root = 1.0 / std::sqrt(3.0);
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G4double xMean = (xInitial + xFinal) / 2.0;
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G4double Step = (xFinal - xInitial) / 2.0;
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G4double delta = Step * root;
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G4double sum = (fFunction(xMean + delta) + fFunction(xMean - delta));
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return sum * Step;
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}
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void G4SimpleIntegration::AdaptGauss(G4double xInitial, G4double xFinal,
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G4double& sum, G4int& depth)
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{
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if(depth > fMaxDepth)
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{
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G4Exception("G4SimpleIntegration::AdaptGauss()", "Error", FatalException,
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"Function varies too rapidly !");
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}
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G4double xMean = (xInitial + xFinal) / 2.0;
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G4double leftHalf = Gauss(xInitial, xMean);
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G4double rightHalf = Gauss(xMean, xFinal);
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G4double full = Gauss(xInitial, xFinal);
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if(std::fabs(leftHalf + rightHalf - full) < fTolerance)
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{
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sum += full;
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}
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else
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{
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++depth;
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AdaptGauss(xInitial, xMean, sum, depth);
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AdaptGauss(xMean, xFinal, sum, depth);
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}
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}
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