Gabriele Cosmo
170 lines
4.0 KiB
C++
170 lines
4.0 KiB
C++
// This code implementation is the intellectual property of
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// the GEANT4 collaboration.
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//
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// By copying, distributing or modifying the Program (or any work
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// based on the Program) you indicate your acceptance of this statement,
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// and all its terms.
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//
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// $Id: G4SimpleIntegration.cc,v 1.2 1999/11/16 17:31:11 gcosmo Exp $
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// GEANT4 tag $Name: geant4-02-00 $
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//
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// Implementation file for simple integration methods
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//
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#include "G4SimpleIntegration.hh"
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G4int G4SimpleIntegration::fMaxDepth = 100 ;
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G4SimpleIntegration::G4SimpleIntegration( function pFunction )
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{
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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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{
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fFunction = pFunction ;
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fTolerance = pTolerance ;
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}
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G4SimpleIntegration::~G4SimpleIntegration()
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{
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;
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}
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// Simple integration methods
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G4double
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G4SimpleIntegration::Trapezoidal(G4double xInitial,
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G4double xFinal,
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G4int iterationNumber )
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{
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G4int i ;
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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(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
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G4SimpleIntegration::MidPoint(G4double xInitial,
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G4double xFinal,
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G4int iterationNumber )
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{
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G4int i ;
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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(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
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G4SimpleIntegration::Gauss(G4double xInitial,
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G4double xFinal,
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G4int iterationNumber )
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{
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G4int i ;
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G4double x ;
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static G4double root = 1.0/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(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
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G4SimpleIntegration::Simpson(G4double xInitial,
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G4double xFinal,
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G4int iterationNumber )
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{
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G4int i ;
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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(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
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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
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G4SimpleIntegration::Gauss( G4double xInitial,
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G4double xFinal )
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{
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static G4double root = 1.0/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
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G4SimpleIntegration::AdaptGauss( G4double xInitial,
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G4double xFinal,
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G4double& sum,
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G4int& depth )
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{
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if(depth >fMaxDepth)
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{
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G4Exception("Function varies too rapidly in G4SimpleIntegration::AdaptGauss") ;
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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(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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