/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_6_2_7/src/CondFormats/CastorObjects/src/CastorPedestalWidth.cc

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#include <math.h>
#include <iostream>

#include "CondFormats/CastorObjects/interface/CastorPedestalWidth.h"

namespace {
  int offset (int fCapId1, int fCapId2) {
    //    static int offsets [4] = {0, 1, 3, 6};
    //    if (fCapId1 < fCapId2) { // swap
    //      int tmp = fCapId1; fCapId1 = fCapId2; fCapId2 = tmp;
    //    }
    //    return offsets [fCapId1] + fCapId2;
    return fCapId1*4 + fCapId2;
  }
}

CastorPedestalWidth::CastorPedestalWidth (int fId) : mId (fId) {
  for (int i = 16; --i >= 0; *(&mSigma00 + i) = 0) {}
}

float CastorPedestalWidth::getWidth (int fCapId) const {
  return sqrt (*(getValues () + offset (fCapId, fCapId)));
}

float CastorPedestalWidth::getSigma (int fCapId1, int fCapId2) const {
  return *(getValues () + offset (fCapId1, fCapId2));
}

void CastorPedestalWidth::setSigma (int fCapId1, int fCapId2, float fSigma) {
  *(&mSigma00 + offset (fCapId1, fCapId2)) = fSigma;
}

// produces pedestal noise in assumption of near correlations and small variations
void CastorPedestalWidth::makeNoise (unsigned fFrames, const double* fGauss, double* fNoise) const {
  double s_xx_mean = (getSigma (0,0) + getSigma (1,1) + getSigma (2,2) + getSigma (3,3)) / 4;
  double s_xy_mean = (getSigma (1,0) + getSigma (2,1) + getSigma (3,2) + getSigma (3,0)) / 4;
  double sigma = sqrt (0.5 * (s_xx_mean + sqrt (s_xx_mean*s_xx_mean - 2*s_xy_mean*s_xy_mean)));
  double corr = sigma == 0 ? 0 : 0.5*s_xy_mean / sigma;
  for (unsigned i = 0; i < fFrames; i++) {
    fNoise [i] = fGauss[i]*sigma;
    if (i > 0) fNoise [i] += fGauss[i-1]*corr;
    if (i < fFrames-1) fNoise [i] += fGauss[i+1]*corr;
  }
}