G4VBiasingInteractionLaw.hh

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//
// G4VBiasingInteractionLaw
//
// Class Description:
//
// An abstract class to model interaction laws, not necessarily.
// exponential ones.
// These laws, p(l), are caraterized by their:
//    - non-interaction probability over l:
//      P_NI(l) = 1 - integral(0,l) p(s) ds
//    - effective cross-section at l:
//      sigma_eff(l) = p(l)/P_NI(l) (several forms exist)
// If several laws compete, the resulting net law has:
//    - an non-interaction probability over a lenght l which
//      is the product of the individual non-interaction probabilities.
//    - an effective cross-section which is the
//      sum on the individual effective cross-sections.
//
// Author: M.Verderi (LLR), November 2013
// --------------------------------------------------------------------
#ifndef G4VBiasingInteractionLaw_hh
#define G4VBiasingInteractionLaw_hh 1
 
#include "globals.hh"
#include <vector>
 
class G4BiasingProcessInterface;
 
class G4VBiasingInteractionLaw
{
  public:
 
    G4VBiasingInteractionLaw(const G4String& name)
      : fName(name), fSampledInteractionLength(DBL_MAX) {}
    virtual ~G4VBiasingInteractionLaw() = default;
 
    const G4String& GetName() const { return fName; }
 
    // -- Compute non-interaction probability and effective cross-section:
    // -- (probability of interaction over dl =  effective_cross-section* dl)
    virtual G4double ComputeNonInteractionProbabilityAt(G4double length) const = 0;
    virtual G4double ComputeEffectiveCrossSectionAt(G4double length) const = 0;
 
    // -- Methods to deal with singularities : null cross sections or infinite ones.
    // -- In such cases, weight can not always be computed.
    // -- Tells if this interaction law has singularities:
    virtual G4bool IsSingular() const { return false; }
    // -- method interrogated only in case interaction law is IsSingular() == true:
    virtual G4bool IsEffectiveCrossSectionInfinite() const { return false; }
 
    // -----------------------------------------
    // -- public interface to protected methods:
    // -----------------------------------------
    G4double Sample()
    {
      fSampledInteractionLength = SampleInteractionLength();
      return fSampledInteractionLength;
    }
    G4double UpdateForStep(G4double truePathLength)
    {
      fSampledInteractionLength = UpdateInteractionLengthForStep(truePathLength);
      return fSampledInteractionLength;
    }
    G4double GetSampledInteractionLength() const
    {
      return fSampledInteractionLength;
    }
 
  protected:
 
    // -- Sample the distribution for point like interaction (PostStep ones)
    virtual G4double SampleInteractionLength() = 0;
 
    // -- Convenience method, used in many daughters classes :
    // -- update the distribution for a made step of truePathLength size:
    virtual G4double UpdateInteractionLengthForStep(G4double /* truePathLength */)
      { return DBL_MAX; }
 
  private:
 
    G4String fName;
    G4double fSampledInteractionLength;
};
 
#endif