/usr/include/CLHEP/Random/RandPoissonQ.h is in libclhep-dev 2.1.4.1-1.2.
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// -*- C++ -*-
//
// -----------------------------------------------------------------------
// HEP Random
// --- RandPoissonQ ---
// class header file
// -----------------------------------------------------------------------
// Class defining RandPoissonQ, which is derived from RandPoison.
// The user interface is identical; but RandGaussQ is much faster in all cases
// and a bit less accurate when mu > 100.
// =======================================================================
// M. Fischler - Created: 4th Feb 2000
// M Fischler - put and get to/from streams 12/10/04
//
// =======================================================================
#ifndef RandPoissonQ_h
#define RandPoissonQ_h 1
#include "CLHEP/Random/defs.h"
#include "CLHEP/Random/Random.h"
#include "CLHEP/Random/RandPoisson.h"
namespace CLHEP {
/**
* @author
* @ingroup random
*/
class RandPoissonQ : public RandPoisson {
public:
inline RandPoissonQ ( HepRandomEngine& anEngine, double b1=1.0 );
inline RandPoissonQ ( HepRandomEngine* anEngine, double b1=1.0 );
// These constructors should be used to instantiate a RandPoissonQ
// distribution object defining a local engine for it.
// The static generator will be skipped using the non-static methods
// defined below.
// If the engine is passed by pointer the corresponding engine object
// will be deleted by the RandPoissonQ destructor.
// If the engine is passed by reference the corresponding engine object
// will not be deleted by the RandPoissonQ destructor.
virtual ~RandPoissonQ();
// Destructor
// Save and restore to/from streams
std::ostream & put ( std::ostream & os ) const;
std::istream & get ( std::istream & is );
// Methods to generate Poisson-distributed random deviates.
// The method used for mu <= 100 is exact, and 3-7 times faster than
// that used by RandPoisson.
// For mu > 100 then we use a corrected version of a
// (quick) Gaussian approximation. Naively that would be:
//
// Poisson(mu) ~ floor( mu + .5 + Gaussian(sqrt(mu)) )
//
// but actually, that would give a slightly incorrect sigma and a
// very different skew than a true Poisson. Instead we return
//
// Poisson(mu) ~ floor( a0*mu + a1*g + a2*g*g ) )
// (with g a gaussian normal)
//
// where a0, a1, a2 are chosen to give the exctly correct mean, sigma,
// and skew for the Poisson distribution.
// Static methods to shoot random values using the static generator
static long shoot( double m=1.0 );
static void shootArray ( const int size, long* vect, double m=1.0 );
// Static methods to shoot random values using a given engine
// by-passing the static generator.
static long shoot( HepRandomEngine* anEngine, double m=1.0 );
static void shootArray ( HepRandomEngine* anEngine,
const int size, long* vect, double m=1.0 );
// Methods using the localEngine to shoot random values, by-passing
// the static generator.
long fire();
long fire( double m );
void fireArray ( const int size, long* vect );
void fireArray ( const int size, long* vect, double m);
double operator()();
double operator()( double m );
std::string name() const;
HepRandomEngine & engine();
static std::string distributionName() {return "RandPoissonQ";}
// Provides the name of this distribution class
// static constants of possible interest to users:
// RandPoisson will never return a deviate greater than this value:
static const double MAXIMUM_POISSON_DEVIATE; // Will be 2.0E9
static inline int tableBoundary();
private:
// constructor helper
void setupForDefaultMu();
// algorithm helper methods - all static since the shoot methods mayneed them
static long poissonDeviateSmall ( HepRandomEngine * e, double mean );
static long poissonDeviateQuick ( HepRandomEngine * e, double mean );
static long poissonDeviateQuick ( HepRandomEngine * e,
double A0, double A1, double A2, double sig );
// All the engine info, and the default mean, are in the
// RandPoisson base class.
// quantities for approximate Poisson by corrected Gaussian
double a0;
double a1;
double a2;
double sigma;
// static data - constants only, so that saveEngineStatus works properly!
// The following MUST MATCH the corresponding values used (in
// poissonTables.cc) when poissonTables.cdat was created.
// poissonTables.cc gets these values by including this header,
// but we must be careful not to change these values,
// and rebuild RandPoissonQ before re-generating poissonTables.cdat.
// (These statics are given values near the start of the .cc file)
static const double FIRST_MU; // lowest mu value in table
static const double LAST_MU; // highest mu value
static const double S; // Spacing between mu values
static const int BELOW; // Starting point for N is at mu - BELOW
static const int ENTRIES; // Number of entries in each mu row
};
} // namespace CLHEP
#ifdef ENABLE_BACKWARDS_COMPATIBILITY
// backwards compatibility will be enabled ONLY in CLHEP 1.9
using namespace CLHEP;
#endif
#include "CLHEP/Random/RandPoissonQ.icc"
#endif
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