* Overlap computation (within LALInferenceLikelihood.c)

REAL8 LALInferenceComputeFrequencyDomainOverlap(LALInferenceIFOData * dataPtr,
                                                COMPLEX16Vector * freqData1,
                                                COMPLEX16Vector * freqData2)
{
  if (dataPtr==NULL || freqData1 ==NULL || freqData2==NULL){
        XLAL_ERROR_REAL8(XLAL_EFAULT);
        }

  int lower, upper, i;
  double deltaT, deltaF;

  double overlap=0.0;

  /* determine frequency range & loop over frequency bins: */
  deltaT = dataPtr->timeData->deltaT;
  deltaF = 1.0 / (((double)dataPtr->timeData->data->length) * deltaT);
  lower = ceil(dataPtr->fLow / deltaF);
  upper = floor(dataPtr->fHigh / deltaF);

  for (i=lower; i<=upper; ++i){
    overlap  += ((4.0*deltaF*(creal(freqData1->data[i])*creal(freqData2->data[i])+cimag(freqData1->data[i])*cimag(freqData2->data[i])))
                 / dataPtr->oneSidedNoisePowerSpectrum->data->data[i]);
  }

  return overlap;
}