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 // -*- C++ -*-
 #ifndef Herwig_MEMultiChannel_H
 #define Herwig_MEMultiChannel_H
 //
 // This is the declaration of the MEMultiChannel class.
 //
 
 #include "ThePEG/MatrixElement/MEBase.h"
 #include "Herwig/Decay/PhaseSpaceMode.fh"
 
 namespace Herwig {
 
 using namespace ThePEG;
 
 /**
  * Here is the documentation of the MEMultiChannel class.
  *
  * @see \ref MEMultiChannelInterfaces "The interfaces"
  * defined for MEMultiChannel.
  */
 class MEMultiChannel: public MEBase {
 
 public:
 
   /**
    * The default constructor.
    */
   MEMultiChannel() {};
 
   /**
    * The destructor.
    */
   virtual ~MEMultiChannel();
   //@}
 
 public:
 
   /** @name Virtual functions required by the MEBase class. */
   //@{
 
   /**
    * The matrix element for the kinematical configuration
    * previously provided by the last call to setKinematics(), suitably
    * scaled by sHat() to give a dimension-less number.
    * @return the matrix element scaled with sHat() to give a
    * dimensionless number.
    */
   double me2() const {return me2(-1);}
 
   /**
    * Return the scale associated with the last set phase space point.
    */
   virtual Energy2 scale() const;
 
   /**
    * The number of internal degrees of freedom used in the matrix
    * element.
    */
   virtual int nDim() const;
 
   /**
    * Generate internal degrees of freedom given nDim() uniform
    * random numbers in the interval \f$ ]0,1[ \f$. To help the phase space
    * generator, the dSigHatDR should be a smooth function of these
    * numbers, although this is not strictly necessary.
    * @param r a pointer to the first of nDim() consecutive random numbers.
    * @return true if the generation succeeded, otherwise false.
    */
   virtual bool generateKinematics(const double * r);
 
   /**
    * Return the matrix element squared differential in the variables
    * given by the last call to generateKinematics().
    */
   virtual CrossSection dSigHatDR() const;
 
   /**
    * Add all possible diagrams with the add() function.
    */
   virtual void getDiagrams() const;
 
   /**
    * Get diagram selector. With the information previously supplied with the
    * setKinematics method, a derived class may optionally
    * override this method to weight the given diagrams with their
    * (although certainly not physical) relative probabilities.
    * @param dv the diagrams to be weighted.
    * @return a Selector relating the given diagrams to their weights.
    */
   virtual Selector<DiagramIndex> diagrams(const DiagramVector & dv) const;
 
   /**
    * Return a Selector with possible colour geometries for the selected
    * diagram weighted by their relative probabilities.
    * @param diag the diagram chosen.
    * @return the possible colour geometries weighted by their
    * relative probabilities.
    */
   virtual Selector<const ColourLines *>
   colourGeometries(tcDiagPtr diag) const;
   //@}
 
 protected :
 
   /**
    *   Add a phase-space mode
    */
   void addMode(PhaseSpaceModePtr mode) {
     modes_.push_back(mode);
   }
 
   /**
    *  Access to the modes
    */
   tPhaseSpaceModePtr mode(unsigned int imode) const {
     return modes_[imode];
   }
   
 public:
 
   /** @name Functions used by the persistent I/O system. */
   //@{
   /**
    * Function used to write out object persistently.
    * @param os the persistent output stream written to.
    */
   void persistentOutput(PersistentOStream & os) const;
 
   /**
    * Function used to read in object persistently.
    * @param is the persistent input stream read from.
    * @param version the version number of the object when written.
    */
   void persistentInput(PersistentIStream & is, int version);
   //@}
 
   /**
    * The standard Init function used to initialize the interfaces.
    * Called exactly once for each class by the class description system
    * before the main function starts or
    * when this class is dynamically loaded.
    */
   static void Init();
 
 protected:
 
   /** @name Standard Interfaced functions. */
   //@{
   /**
    * Initialize this object after the setup phase before saving an
    * EventGenerator to disk.
    * @throws InitException if object could not be initialized properly.
    */
   virtual void doinit();
 
   /**
    * Initialize this object. Called in the run phase just before
    * a run begins.
    */
   virtual void doinitrun();
   //@}
 
 protected:
 
   /**
    * Return the matrix element squared for a given mode and phase-space channel.
    * @param ichan The channel we are calculating the matrix element for. 
    * @param part The decaying Particle.
    * @param outgoing The particles produced in the decay
    * @param momenta  The momenta of the particles produced in the decay
    * @param meopt Option for the calculation of the matrix element
    * @return The matrix element squared for the phase-space configuration.
    */
   virtual double me2(const int ichan) const = 0;
 
   /**
    *   Access the mode currently being used
    */
   unsigned int iMode() {return iMode_;}
 
   /**
    *  Set the mode currently begining used
    */
   void iMode(unsigned int in) const {iMode_=in;}
 
 private:
 
   /**
    * The assignment operator is private and must never be called.
    * In fact, it should not even be implemented.
    */
   MEMultiChannel & operator=(const MEMultiChannel &) = delete;
 
 private:
 
   /**
    *   The phase-space modes
    */
   vector<PhaseSpaceModePtr> modes_;
 
   /**
    *   Map from the phase space channels to the modes
    */
   mutable vector<map <int,int> > channelMap_;
 
   /**
    *   The mode currently begining used
    */
   mutable unsigned int iMode_;
 };
 
 }
 
 #endif /* Herwig_MEMultiChannel_H */

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