Implementation of the JGenerator interface. More...

#include <JMarkovGenerator.hh>

Inheritance diagram for JMARKOV::JSphereGenerator:

Public Member Functions
	JSphereGenerator (const JPosition3D &_x0, double _r=0, TH2 *_h=NULL)
	Constructor.

	~JSphereGenerator ()

JPosition3D	getPosition ()
	Return a randomly generated position.

double	getWeight (JPosition3D pos)
	return the weight (=probability density dP/dV) for the given position.

Public Attributes
JPosition3D	x0

double	r

TH2 *	h

Detailed Description

Implementation of the JGenerator interface.

Generates positions on a sphere of radius _r centered at _x0 by sampling from a 2D histogram of cosTheta vs phi.

When r=0, it simply returns the position x0.

Definition at line 586 of file JMarkovGenerator.hh.

Constructor & Destructor Documentation

◆ JSphereGenerator()

JMARKOV::JSphereGenerator::JSphereGenerator	(	const JPosition3D &	_x0,
		double	_r = 0,
		TH2 *	_h = NULL )

inline

Constructor.

The histogram is cloned and automatically normalized. The x-axis is assumed to be cos(theta), and the y-axis is assumed to be phi in radians. Empty bins should be avoided!

Definition at line 596 of file JMarkovGenerator.hh.

                                                                          : x0(_x0), r(_r) {
 
      using namespace std;
      using namespace JPP;
 
      h = NULL ;
 
      if( r>0 ) {
        // copy histogram
        h = (TH2*) _h->Clone( _h->GetName() ) ;
        // check that it has the proper limits
        if( h->GetXaxis()->GetXmin()<-1 || h->GetXaxis()->GetXmax()>1 ) {
          cerr << "FATAL ERROR in JSphereGenerator. Invalid x-axis range." << endl ;
          exit(1) ;
        }
        if( h->GetYaxis()->GetXmin() < -M_PI || h->GetYaxis()->GetXmax() > M_PI ) {
          cerr << "FATAL ERROR in JSphereGenerator. Invalid y-axis range." << endl ;
          exit(1) ;
        }
        // normalize histogram
        h->Scale( 1.0/h->Integral("width") ) ;
        h->SetOption("colz") ;
      }
    }

◆ ~JSphereGenerator()

JMARKOV::JSphereGenerator::~JSphereGenerator ( )

inline

Definition at line 621 of file JMarkovGenerator.hh.

                        {
      delete h ;
    }

Member Function Documentation

◆ getPosition()

JPosition3D JMARKOV::JSphereGenerator::getPosition ( )

inlinevirtual

Return a randomly generated position.

Implements JMARKOV::JGenerator.

Definition at line 625 of file JMarkovGenerator.hh.

                              {
 
      using namespace std;
      using namespace JPP;
 
      if( r==0 ) return x0 ;
 
      double costheta, phi ;
      h->GetRandom2(costheta,phi) ;
      return x0 + r * JPosition3D(JAngle3D(acos(costheta),phi));
    }

◆ getWeight()

double JMARKOV::JSphereGenerator::getWeight ( JPosition3D pos )

inlinevirtual

return the weight (=probability density dP/dV) for the given position.

When the generator is properly normalized, the integral of this quantity over the whole space is 1.

Implements JMARKOV::JGenerator.

Definition at line 637 of file JMarkovGenerator.hh.

                                        {
 
      using namespace std;
      using namespace JPP;
 
      if( r==0 ) return 1 ;
 
      // check that the position is in fact on the target surface
      const double tolerance = 1e-5 ;
      if( fabs( pos.getDistance(x0)-r ) > tolerance*r ) {
        return 0.0 ;
      }
 
      JDirection3D dir(pos-x0) ;
      double ct = dir.getDZ() ;
      double phi = dir.getPhi() ;
 
      if( ct < h->GetXaxis()->GetXmin() || ct >=h->GetXaxis()->GetXmax() ) return 0.0 ;
      if( phi< h->GetYaxis()->GetXmin() || phi>=h->GetYaxis()->GetXmax() ) return 0.0 ;
 
      Int_t bin = h->FindBin(ct,phi) ;
      return h->GetBinContent(bin) / (r*r) ;
    }