GaussNoiseProducerFP420 Class Reference

#include <GaussNoiseProducerFP420.h>

List of all members.

Public Member Functions
	GaussNoiseProducerFP420 ()
void	generate (int NumberOfchannels, float threshold, float noiseRMS, std::map< int, float, std::less< int > > &theMap)
	~GaussNoiseProducerFP420 ()

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Detailed Description

Definition at line 6 of file GaussNoiseProducerFP420.h.

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Constructor & Destructor Documentation

GaussNoiseProducerFP420::GaussNoiseProducerFP420

(

)

[inline]

Definition at line 10 of file GaussNoiseProducerFP420.h.

{}

GaussNoiseProducerFP420::~GaussNoiseProducerFP420

(

)

[inline]

Definition at line 11 of file GaussNoiseProducerFP420.h.

{}

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Member Function Documentation

void GaussNoiseProducerFP420::generate	(	int	NumberOfchannels,
		float	threshold,
		float	noiseRMS,
		std::map< int, float, std::less< int > > &	theMap
	)

Definition at line 18 of file GaussNoiseProducerFP420.cc.

References benchmark_cfg::cerr, i, query::result, and ntuplemaker::status.

Referenced by GaussNoiseFP420::addNoise().

{
  
  // estimale mean number of noisy channels with amplidudes above $AdcThreshold$
  
  // Gauss is centered at 0 with sigma=1
  // Gaussian tail probability higher threshold(=5sigma for instance):
  gsl_sf_result result;
  int status = gsl_sf_erf_Q_e(threshold, &result);
  //MP 
  //  if (status != 0) throw DetLogicError("GaussNoiseProducerFP420::could not compute gaussian tail probability for the threshold chosen");
  if (status != 0) std::cerr<<"GaussNoiseProducerFP420::could not compute gaussian tail probability for the threshold chosen"<<std::endl;
  float probabilityLeft = result.val;
  
  // with known probability higher threshold compute number of noisy channels distributed in Poisson:
  float meanNumberOfNoisyChannels = probabilityLeft * NumberOfchannels;
  int numberOfNoisyChannels = CLHEP::RandPoisson::shoot(meanNumberOfNoisyChannels);
  
  // draw noise at random according to Gaussian tail
  
  // initialise default gsl uniform generator engine
  static gsl_rng * mt19937 = gsl_rng_alloc (gsl_rng_mt19937);
  
  float lowLimit = threshold * noiseRMS;
  for (int i = 0; i < numberOfNoisyChannels; i++) {
    
    // Find a random channel number    
    int theChannelNumber = (int) CLHEP::RandFlat::shootInt(NumberOfchannels);
    
    // Find random noise value: random mt19937 over Gaussian tail above threshold:
    float noise = gsl_ran_gaussian_tail(mt19937, lowLimit, noiseRMS);
    
    // Fill in map
    theMap[theChannelNumber] = noise;
    
  }
}