GammaNumericalGenerator.h

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#ifndef GammaNumericalGenerator_H
#define GammaNumericalGenerator_H
#include "FastSimulation/Utilities/interface/BaseNumericalRandomGenerator.h"

#include <cmath>
class RandomEngineAndDistribution;

class GammaNumericalGenerator : public BaseNumericalRandomGenerator
{
 public:

   GammaNumericalGenerator(double a=0,double b=0,double x1=0,double x2=0) :
     BaseNumericalRandomGenerator(x1,x2,1000),
     a_(a),b_(b),valid(false) {

    if(a>0&&b>0) 
      {
    valid=true;
    initialize();
      }
  }

  virtual ~GammaNumericalGenerator() {}

  double gamma(RandomEngineAndDistribution const* random) const { return generate(random); }
  
  double gamma_exp(RandomEngineAndDistribution const* random) const {return generateExp(random);}

  double gamma_lin(RandomEngineAndDistribution const* random) const {return generateLin(random);}

  virtual double function(double x) { return ersatzt(x); }

  inline bool isValid() const {return valid;}

 private:

  double ersatzt(double x) { 
    double bt=b_*x;
    return  b_*pow(bt,a_-1)*exp(-bt);
  }
  
  // gamma distribution parameters 
  double a_,b_;
  bool valid;
};

#endif