G4ParticleHPArbitaryTab.cc

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//
// neutron_hp -- source file
// J.P. Wellisch, Nov-1996
// A prototype of the low energy neutron transport model.
//
// P. Arce, June-2014 Conversion neutron_hp to particle_hp
//
#include "G4ParticleHPArbitaryTab.hh"
 
#include "G4ios.hh"
 
G4double G4ParticleHPArbitaryTab::Sample(G4double anEnergy)
{
  G4int i;
  for (i = 0; i < nDistFunc; i++) {
    if (anEnergy < theDistFunc[i].GetLabel()) break;  // that is the energy we need
  }
  G4int low(0), high(0);
  if (i == nDistFunc) {
    low = i - 2;
    high = i - 1;
  }
  else if (i == 0) {
    if (nDistFunc == 0) {
      G4cerr << "No distribution functions to sample "
             << "from in G4ParticleHPArbitaryTab::Sample" << G4endl;
      throw G4HadronicException(__FILE__, __LINE__, "nDistFunc==0");
    }
    return theDistFunc[0].Sample();
  }
  else {
    low = i - 1;
    high = i;
  }
  //************************************************************************
  // EMendoza
  /*
    theBuffer.Merge(theManager.GetScheme(low), anEnergy,
    theDistFunc+low, theDistFunc+high);
    return theBuffer.Sample();
  */
  //************************************************************************
  // New way to perform the 2D sampling:
  G4double elow = theDistFunc[low].GetLabel();
  G4double ehigh = theDistFunc[high].GetLabel();
  G4double rval = (anEnergy - elow) / (ehigh - elow);  // rval is 0 for elow and 1 for ehigh
  G4double eoutlow = theLowThreshold[low] + rval * (theLowThreshold[high] - theLowThreshold[low]);
  G4double eouthigh =
    theHighThreshold[low] + rval * (theHighThreshold[high] - theHighThreshold[low]);
  G4double rand = G4UniformRand();
  G4double Eout_1 = 0, Eout_2 = 0;
  if (rval < rand) {
    Eout_1 = theDistFunc[low].Sample();
    Eout_2 = eoutlow
             + (Eout_1 - theLowThreshold[low]) * (eouthigh - eoutlow)
                 / (theHighThreshold[low] - theLowThreshold[low]);
  }
  else {
    Eout_1 = theDistFunc[high].Sample();
    Eout_2 = eoutlow
             + (Eout_1 - theLowThreshold[high]) * (eouthigh - eoutlow)
                 / (theHighThreshold[high] - theLowThreshold[high]);
  }
  return Eout_2;
 
  //************************************************************************
}