CRandom.cpp
No OneTemporary
Actions

Size

1 KB

Subscribers

None

CRandom.cpp
View Options

	#include "CRandom.h"

	float const CRandom::pi=acos(-1.);
	bool CRandom::one = 1;
	float CRandom::angle = 0.;
	float CRandom::x=0.;

	/**
	* Returns a random number with uniform distribution between 0 and 1
	*/
	double CRandom::Rndm()
	{
	return (float)rand()/(float)RAND_MAX;
	}
	//***********************
	/**
	* Returns random number with Gaussian distribution
	\param mean is the mean value of the Gaussian distribution
	\param sigma is the standard deviation of the distribution
	*/
	float CRandom::Gaus(float mean, float sigma)
	{
	float r;
	if (one)
	{
	x = sqrt(-2.*log(Rndm()+1.e-37));
	angle = 2.piRndm();
	one = 0;
	r = x*cos(angle);
	}
	else
	{
	r = x*sin(angle);
	one = 1;
	}


	return sigma*r + mean;
	}
	//*************************
	/**
	* returns a decay time in zs sampled from a exponential distribution
	\param width is the total decay width in MeV
	*/
	float CRandom::expDecayTime(float width)
	{
	// returns a time from an exponential decay distribution
	//consistent with the total decay width
	return - 0.65824*log(Rndm()+1.0e-37)/width;
	}
	//****************************************
	/**
	* Returns a random number with a BreitWigner distribution
	\param mean is the mean value of the distribution
	\param width is the Full Width Half max of the distribution
	*/

	float CRandom::BreitWigner(float mean, float width)
	{
	float xx = (1.-2.Rndm())pi/2.;
	float yy = tan(xx)/2.;

	return yy*width + mean;
	}