Gabriele Cosmo
169 lines
5.9 KiB
C++
169 lines
5.9 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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//
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// -------------------------------------------------------------------
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//
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// GEANT4 Class header file
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//
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//
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// File name: G4EmElementSelector
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//
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// Author: Vladimir Ivanchenko
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//
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// Creation date: 29.05.2008
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//
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// Modifications:
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//
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//
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// Class Description:
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//
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// Generic helper class for the random selection of an element
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// -------------------------------------------------------------------
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//
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#ifndef G4EmElementSelector_h
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#define G4EmElementSelector_h 1
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#include "globals.hh"
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#include "G4ParticleDefinition.hh"
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#include "G4Material.hh"
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#include "G4Element.hh"
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#include "G4ElementVector.hh"
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#include "G4PhysicsLogVector.hh"
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#include "Randomize.hh"
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#include <vector>
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class G4VEmModel;
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class G4EmElementSelector
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{
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public:
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G4EmElementSelector(G4VEmModel*, const G4Material*, G4int bins,
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G4double emin, G4double emax,
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G4bool spline = true);
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~G4EmElementSelector();
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void Initialise(const G4ParticleDefinition*, G4double cut = 0.0);
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void Dump(const G4ParticleDefinition* p = nullptr);
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inline const G4Element* SelectRandomAtom(G4double kineticEnergy) const;
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inline const G4Element* SelectRandomAtom(const G4double kineticEnergy,
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const G4double logEKin) const;
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inline const G4Material* GetMaterial() const;
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private:
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// hide assignment operator
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G4EmElementSelector & operator=(const G4EmElementSelector &right) = delete;
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G4EmElementSelector(const G4EmElementSelector&) = delete;
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G4VEmModel* model;
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const G4Material* material;
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const G4ElementVector* theElementVector;
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G4int nElmMinusOne;
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G4int nbins;
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G4double cutEnergy;
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G4double lowEnergy;
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G4double highEnergy;
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std::vector<G4PhysicsLogVector*> xSections;
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};
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
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inline const G4Element* G4EmElementSelector::SelectRandomAtom(G4double e) const
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{
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const G4Element* element = (*theElementVector)[nElmMinusOne];
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if (nElmMinusOne > 0) {
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G4double x = G4UniformRand();
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size_t idx(0);
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for(G4int i=0; i<nElmMinusOne; ++i) {
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if (x <= (xSections[i])->Value(e, idx)) {
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element = (*theElementVector)[i];
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break;
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}
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}
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}
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return element;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
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inline const G4Element*
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G4EmElementSelector::SelectRandomAtom(const G4double e,const G4double loge)const
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{
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const G4Element* element = (*theElementVector)[nElmMinusOne];
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if (nElmMinusOne > 0) {
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// 1. Determine energy index (only once)
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const size_t nBins = (xSections[0])->GetVectorLength();
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// handle cases below/above the enrgy grid (by ekin, idx that gives a=0/1)
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// ekin = x[0] if e<=x[0] and idx will be 0 ^ a=0 => so y=y0
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// ekin = x[N-1] if e>=x[N-1] and idx will be N-2 ^ a=1 => so y=y_{N-1}
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const G4double ekin = std::max((xSections[0])->Energy(0),
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std::min((xSections[0])->Energy(nBins-1),e));
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// compute the lower index of the bin (idx \in [0,N-2] will be guaranted)
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const size_t idx = (xSections[0])->ComputeLogVectorBin(loge);
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// 2. Do the linear interp.(robust for corner cases through ekin, idx and a)
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const G4double x1 = (xSections[0])->Energy(idx);
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const G4double x2 = (xSections[0])->Energy(idx+1);
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// note: all corner cases of the previous methods are covered and eventually
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// gives a=0/1 that results in y=y0\y_{N-1} if e<=x[0]/e>=x[N-1] or
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// y=y_i/y_{i+1} if e<x[i]/e>=x[i+1] due to small numerical errors
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const G4double a = std::max(0., std::min(1., (ekin - x1)/(x2 - x1)));
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const G4double urnd = G4UniformRand();
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for (G4int i = 0; i < nElmMinusOne; ++i) {
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const G4double y1 = (*xSections[i])[idx];
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const G4double y2 = (*xSections[i])[idx+1];
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if (urnd <= y1 + a*(y2-y1)) {
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element = (*theElementVector)[i];
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break;
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}
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}
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}
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return element;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
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inline const G4Material* G4EmElementSelector::GetMaterial() const
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{
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return material;
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}
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//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo.....
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#endif
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