ThermalNeutronBk2BkExpConvPVoigt.cpp

// Mantid Repository : https://github.com/mantidproject/mantid
//
// Copyright © 2018 ISIS Rutherford Appleton Laboratory UKRI,
//   NScD Oak Ridge National Laboratory, European Spallation Source,
//   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
// SPDX - License - Identifier: GPL - 3.0 +
#include "MantidCurveFitting/Functions/ThermalNeutronBk2BkExpConvPVoigt.h"
#include "MantidAPI/FunctionFactory.h"
#include "MantidAPI/ParamFunction.h"
#include "MantidKernel/EmptyValues.h"
#include "MantidKernel/Logger.h"

#include "MantidKernel/ConfigService.h"

#include <boost/lexical_cast.hpp>
#include <cmath>
#include <gsl/gsl_sf_erf.h>

const double PEAKRANGE = 5.0;
const double NEG_DBL_MAX = -1. * DBL_MAX;

using namespace std;

using namespace Mantid;

using namespace Mantid::API;

namespace Mantid::CurveFitting::Functions {

using namespace CurveFitting;
namespace {
/// static reference to the logger
Kernel::Logger g_log("ThermalNeutronBk2BkExpConvPV");
} // namespace

DECLARE_FUNCTION(ThermalNeutronBk2BkExpConvPVoigt)

//----------------------------------------------------------------------------------------------
/** Constructor
 */
ThermalNeutronBk2BkExpConvPVoigt::ThermalNeutronBk2BkExpConvPVoigt()
    : IPowderDiffPeakFunction(), m_Alpha(0.), m_Beta(0.), m_Sigma2(0.), m_Gamma(0.), m_eta(0.), m_N(0.),
      m_cancel(false), m_parallelException(false), m_dspaceCalculated(false) {
  mHKLSet = false;
}

//----------------------------------------------------------------------------------------------
/** Define the fittable parameters
 * Notice that Sig0, Sig1 and Sig2 are NOT the squared value recorded in
 * Fullprof
 */
void ThermalNeutronBk2BkExpConvPVoigt::init() {
  // Peak height (0)
  declareParameter("Height", 1.0, "Intensity of peak");

  // Instrument geometry related (1 ~ 8)
  declareParameter("Dtt1", 1.0, "coefficient 1 for d-spacing calculation for epithermal neutron part");
  declareParameter("Dtt2", 1.0, "coefficient 2 for d-spacing calculation for epithermal neutron part");
  declareParameter("Dtt1t", 1.0, "coefficient 1 for d-spacing calculation for thermal neutron part");
  declareParameter("Dtt2t", 1.0, "coefficient 2 for d-spacing calculation for thermal neutron part");
  declareParameter("Zero", 0.0, "Zero shift for epithermal neutron");
  declareParameter("Zerot", 0.0, "Zero shift for thermal neutron");
  declareParameter("Width", 1.0, "width of the crossover region");
  declareParameter("Tcross", 1.0, "position of the centre of the crossover region");

  // Peak profile related (9 ~ 16) Back to back Expoential
  declareParameter("Alph0", 1.6, "exponential constant for rising part of epithermal neutron pulse");
  declareParameter("Alph1", 1.5, "exponential constant for rising part of expithermal neutron pulse");
  declareParameter("Beta0", 1.6, "exponential constant of decaying part of epithermal neutron pulse");
  declareParameter("Beta1", 1.5, "exponential constant of decaying part of epithermal neutron pulse");
  declareParameter("Alph0t", 1.6, "exponential constant for rising part of thermal neutron pulse");
  declareParameter("Alph1t", 1.5, "exponential constant for rising part of thermal neutron pulse");
  declareParameter("Beta0t", 1.6, "exponential constant of decaying part of thermal neutron pulse");
  declareParameter("Beta1t", 1.5, "exponential constant of decaying part of thermal neutron pulse");

  // Pseudo-Voigt (17 ~ 22)
  declareParameter("Sig0", 1.0,
                   "variance parameter 1 of the Gaussian "
                   "component of the psuedovoigt function");
  declareParameter("Sig1", 1.0,
                   "variance parameter 2 of the Gaussian "
                   "component of the psuedovoigt function");
  declareParameter("Sig2", 1.0,
                   "variance parameter 3 of the Gaussian "
                   "component of the psuedovoigt function");

  declareParameter("Gam0", 0.0,
                   "FWHM parameter 1 of the Lorentzian component "
                   "of the psuedovoigt function");
  declareParameter("Gam1", 0.0,
                   "FWHM parameter 2 of the Lorentzian component "
                   "of the psuedovoigt function");
  declareParameter("Gam2", 0.0,
                   "FWHM parameter 3 of the Lorentzian component "
                   "of the psuedovoigt function");

  // Lattice parameter (23)
  declareParameter("LatticeConstant", 10.0, "lattice constant for the sample");

  LATTICEINDEX = 23;
  HEIGHTINDEX = 0;

  // Unit cell
  m_unitCellSize = 10.0;

  // Set flag
  m_cellParamValueChanged = true;
}

//------------- Public Functions (Overwrite) Set/Get
//---------------------------------------------

//------------- Public Functions (New) Set/Get
//-------------------------------------------------

//----------------------------------------------------------------------------------------------
/** Set Miller Indices for this peak
void ThermalNeutronBk2BkExpConvPVoigt::setMillerIndex(int h, int k, int l)
{
  // Check validity and set flag
  if (mHKLSet)
  {
    // Throw exception if tried to reset the miller index
    stringstream errss;
    errss << "ThermalNeutronBk2BkExpConvPVoigt Peak cannot have (HKL) reset.";
    g_log.error(errss.str());
    throw runtime_error(errss.str());
  }
  else
  {
    // Set flag
    mHKLSet = true;
  }

  // Set value
  mH = static_cast<int>(h);
  mK = static_cast<int>(k);
  mL = static_cast<int>(l);

  // Check value valid or not
  if (mH*mH + mK*mK + mL*mL < 1.0E-8)
  {
    stringstream errmsg;
    errmsg << "H = K = L = 0 is not allowed";
    g_log.error(errmsg.str());
    throw std::invalid_argument(errmsg.str());
  }

  return;
}
   */

//----------------------------------------------------------------------------------------------
/** Get Miller Index from this peak
void ThermalNeutronBk2BkExpConvPVoigt::getMillerIndex(int& h, int &k, int &l)
{
  h = static_cast<int>(mH);
  k = static_cast<int>(mK);
  l = static_cast<int>(mL);

  return;
}
*/

//----------------------------------------------------------------------------------------------
/** Get peak parameters stored locally
 * Get some internal parameters values including
 * (a) Alpha, (b) Beta, (c) Gamma, (d) Sigma2
 * Exception: if the peak profile parameter is not in this peak, then
 *            return an Empty_DBL
 */
double ThermalNeutronBk2BkExpConvPVoigt::getPeakParameter(const std::string &paramname) {
  // 1. Calculate peak parameters if required
  if (m_hasNewParameterValue) {
    calculateParameters(false);
  }

  // 2. Get value
  double paramvalue;

  if (paramname == "Alpha")
    paramvalue = m_Alpha;
  else if (paramname == "Beta")
    paramvalue = m_Beta;
  else if (paramname == "Sigma2")
    paramvalue = m_Sigma2;
  else if (paramname == "Gamma")
    paramvalue = m_Gamma;
  else if (paramname == "d_h")
    paramvalue = m_dcentre;
  else if (paramname == "Eta")
    paramvalue = m_eta;
  else if (paramname == "TOF_h")
    paramvalue = m_centre;
  else if (paramname == "FWHM")
    paramvalue = m_fwhm;
  else {
    stringstream errss;
    errss << "Parameter " << paramname << " does not exist in peak function " << this->name()
          << "'s calculated parameters. "
          << "Candidates are Alpha, Beta, Sigma2, Gamma d_h and Eta. ";
    throw runtime_error(errss.str());
  }

  return paramvalue;
}

//------------- Public Functions (Overwrite) Calculation
//---------------------------------------------
/** Calculate peak parameters (fundamential Back-to-back PV),including
 * alpha, beta, sigma^2, eta, H
 */
void ThermalNeutronBk2BkExpConvPVoigt::calculateParameters(bool explicitoutput) const {
  // Obtain parameters (class) with pre-set order
  double dtt1 = getParameter(1);
  double dtt1t = getParameter(3);
  double dtt2t = getParameter(4);
  double zero = getParameter(5);
  double zerot = getParameter(6);
  double wcross = getParameter(7);
  double Tcross = getParameter(8);

  double alph0 = getParameter(9);
  double alph1 = getParameter(10);
  double beta0 = getParameter(11);
  double beta1 = getParameter(12);
  double alph0t = getParameter(13);
  double alph1t = getParameter(14);
  double beta0t = getParameter(15);
  double beta1t = getParameter(16);

  double sig0 = getParameter(17);
  double sig1 = getParameter(18);
  double sig2 = getParameter(19);
  double gam0 = getParameter(20);
  double gam1 = getParameter(21);
  double gam2 = getParameter(22);

  double latticeconstant = getParameter(LATTICEINDEX);

  double dh, tof_h, eta, alpha, beta, H, sigma2, gamma, N;

  // Calcualte Peak Position d-spacing and TOF
  if (m_cellParamValueChanged) {
    m_unitCell.set(latticeconstant, latticeconstant, latticeconstant, 90.0, 90.0, 90.0);
    dh = m_unitCell.d(mH, mK, mL);
    m_dcentre = dh;
    m_cellParamValueChanged = false;
  } else {
    dh = m_dcentre;
  }

  // Calculate all the parameters
  // - Start to calculate alpha, beta, sigma2, gamma,
  double n = 0.5 * gsl_sf_erfc(wcross * (Tcross - 1 / dh));

  double alpha_e = alph0 + alph1 * dh;
  double alpha_t = alph0t - alph1t / dh;
  alpha = 1 / (n * alpha_e + (1 - n) * alpha_t);

  double beta_e = beta0 + beta1 * dh;
  double beta_t = beta0t - beta1t / dh;
  beta = 1 / (n * beta_e + (1 - n) * beta_t);

  double Th_e = zero + dtt1 * dh;
  double Th_t = zerot + dtt1t * dh - dtt2t / dh;
  tof_h = n * Th_e + (1 - n) * Th_t;

  sigma2 = sig0 * sig0 + sig1 * sig1 * std::pow(dh, 2) + sig2 * sig2 * std::pow(dh, 4);
  gamma = gam0 + gam1 * dh + gam2 * std::pow(dh, 2);

  // - Calcualte H for the peak
  calHandEta(sigma2, gamma, H, eta);

  N = alpha * beta * 0.5 / (alpha + beta);

  // Record recent value
  m_Alpha = alpha;
  m_Beta = beta;
  m_Sigma2 = sigma2;
  m_Gamma = gamma;
  m_fwhm = H;
  m_centre = tof_h;
  m_N = N;
  m_eta = eta;

  // Check whether all the parameters are physical
  if (alpha != alpha || beta != beta || sigma2 != sigma2 || gamma != gamma || H != H || H <= 0.) {
    m_parameterValid = false;
  } else {
    m_parameterValid = true;
  }

  // 5.Debug output
  if (explicitoutput) {
    stringstream errss;
    errss << "alpha = " << alpha << ", beta = " << beta << ", N = " << N << "\n";
    errss << "  n = " << n << ", alpha_e = " << alpha_e << ", alpha_t = " << alpha_t << "\n";
    errss << " dh = " << dh << ", alph0t = " << alph0t << ", alph1t = " << alph1t << ", alph0 = " << alph0
          << ", alph1 = " << alph1 << "\n";
    errss << "  n = " << n << ", beta_e = " << beta_e << ", beta_t = " << beta_t << "\n";
    errss << " dh = " << dh << ", beta0t = " << beta0t << ", beta1t = " << beta1t << "\n";
    g_log.information(errss.str());
  }

  // Reset the flag
  m_hasNewParameterValue = false;
}

//------------- Private Functions (Overwrite) Calculation
//--------------------------------------

//----------------------------------------------------------------------------------------------
/** Override function1D
 */
void ThermalNeutronBk2BkExpConvPVoigt::functionLocal(double *out, const double *xValues, size_t nData) const {
  // 1. Calculate peak parameters
  double height = getParameter(0);

  // double d_h, tof_h, alpha, beta, H, sigma2, eta, N, gamma;
  // d_h, tof_h, eta, alpha, beta, H, sigma2, gamma, N,

  if (m_hasNewParameterValue)
    calculateParameters(false);

  double peakrange = m_fwhm * PEAKRANGE;

  // cout << "DBx212:  eta = " << eta << ", gamma = " << gamma << '\n';

  double invert_sqrt2sigma = 1.0 / sqrt(2.0 * m_Sigma2);

  // PRAGMA_OMP(parallel for schedule(dynamic, 10))

  // PARALLEL_SET_NUM_THREADS(8);
  // PARALLEL_FOR_NO_WSP_CHECK()
  for (size_t id = 0; id < nData; ++id) {
    // PARALLEL_START_INTERRUPT_REGION

    // a) Caclualte peak intensity
    double dT = xValues[id] - m_centre;

    double omega;
    if (fabs(dT) < peakrange) {
      omega = calOmega(dT, m_eta, m_N, m_Alpha, m_Beta, m_fwhm, m_Sigma2, invert_sqrt2sigma);
      omega *= height;
    } else {
      omega = 0.0;
    }

    out[id] = omega;

    /*  Disabled for parallel checking
    if (!(omega > -DBL_MAX && omega < DBL_MAX))
    {
     // Output with error
     g_log.error() << "Calcuate Peak " << mH << ", " << mK << ", " << mL << "
    wrong!\n";
     bool explicitoutput = true;
     calculateParameters(d_h, tof_h, eta, alpha, beta, H, sigma2, gamma, N,
    explicitoutput);
     calOmega(dT, eta, N, alpha, beta, H, sigma2, invert_sqrt2sigma,
    explicitoutput);

      out[id] = DBL_MAX;
    }
    else
    {
      out[id] = height*omega;
    }
    */

    // PARALLEL_END_INTERRUPT_REGION
  } // ENDFOR data points
  // PARALLEL_CHECK_INTERRUPT_REGION
}

//----------------------------------------------------------------------------------------------
/** Function (local) of the vector version
 * @param out: The calculated peak intensities. This is assume to been
 * initialized to the correct length
 * with a value of zero everywhere.
 * @param xValues: The x-values to evaluate the peak at.
 */
void ThermalNeutronBk2BkExpConvPVoigt::function(vector<double> &out, const vector<double> &xValues) const {
  // calculate peak parameters
  const double HEIGHT = getParameter(0);
  const double INVERT_SQRT2SIGMA = 1.0 / sqrt(2.0 * m_Sigma2);

#if 0
    g_log.notice() << "HEIGHT = " << HEIGHT << ".\n";

#endif
  if (m_hasNewParameterValue)
    calculateParameters(false);

  const double RANGE = m_fwhm * PEAKRANGE;

  // calculate where to start calculating
  const double LEFT_VALUE = m_centre - RANGE;
  auto iter = std::lower_bound(xValues.begin(), xValues.end(), LEFT_VALUE);

  const double RIGHT_VALUE = m_centre + RANGE;
  auto iter_end = std::lower_bound(iter, xValues.end(), RIGHT_VALUE);

  // 2. Calcualte
  std::size_t pos(std::distance(xValues.begin(), iter)); // second loop variable
  for (; iter != iter_end; ++iter) {
    out[pos] = HEIGHT * calOmega(*iter - m_centre, m_eta, m_N, m_Alpha, m_Beta, m_fwhm, m_Sigma2, INVERT_SQRT2SIGMA);
    pos++;
  } // ENDFOR data points
}

//----------------------------------------------------------------------------------------------
/** Disabled derivative
 */
void ThermalNeutronBk2BkExpConvPVoigt::functionDerivLocal(API::Jacobian * /*unused*/, const double * /*unused*/,
                                                          const size_t /*unused*/) {
  throw Mantid::Kernel::Exception::NotImplementedError("functionDerivLocal is not implemented for IkedaCarpenterPV.");
}

/** Calculate derivative of this peak function
 */
void ThermalNeutronBk2BkExpConvPVoigt::functionDeriv(const API::FunctionDomain &domain, API::Jacobian &jacobian) {
  calNumericalDeriv(domain, jacobian);
}

/** Get the center of the peak

double ThermalNeutronBk2BkExpConvPVoigt::centre()const
{
  if (m_newValueSet)
    calculateParameters(false);

  return m_centre;
}
 */

/** Set peak height

void ThermalNeutronBk2BkExpConvPVoigt::setHeight(const double h)
{
  setParameter(HEIGHTINDEX, h);

  return;
}
   */

/** Get peak's height
double ThermalNeutronBk2BkExpConvPVoigt::height() const
{
  double height = this->getParameter(HEIGHTINDEX);
  return height;
}
  */

/** Get peak's FWHM

double ThermalNeutronBk2BkExpConvPVoigt::fwhm() const
{
  if (m_newValueSet)
    calculateParameters(false);

  return m_fwhm;
}
   */

//-------------  Private Function To Calculate Peak Profile
//--------------------------------------------
/** Calcualte H and eta for the peak
 */
void ThermalNeutronBk2BkExpConvPVoigt::calHandEta(double sigma2, double gamma, double &H, double &eta) const {
  // 1. Calculate H
  double H_G = sqrt(8.0 * sigma2 * M_LN2);
  double H_L = gamma;

  double temp1 = std::pow(H_L, 5) + 0.07842 * H_G * std::pow(H_L, 4) + 4.47163 * std::pow(H_G, 2) * std::pow(H_L, 3) +
                 2.42843 * std::pow(H_G, 3) * std::pow(H_L, 2) + 2.69269 * std::pow(H_G, 4) * H_L + std::pow(H_G, 5);

  H = std::pow(temp1, 0.2);

  // 2. Calculate eta
  double gam_pv = H_L / H;
  eta = 1.36603 * gam_pv - 0.47719 * std::pow(gam_pv, 2) + 0.11116 * std::pow(gam_pv, 3);

  if (eta > 1 || eta < 0) {
    g_log.warning() << "Calculated eta = " << eta << " is out of range [0, 1].\n";
  }
}

//----------------------------------------------------------------------------------------------
/** Calculate Omega(x) = ... ...
 * This is the core component to calcualte peak profile
 */
double ThermalNeutronBk2BkExpConvPVoigt::calOmega(const double x, const double eta, const double N, const double alpha,
                                                  const double beta, const double H, const double sigma2,
                                                  const double invert_sqrt2sigma, const bool explicitoutput) const {
  const double u = 0.5 * alpha * (alpha * sigma2 + 2. * x);
  const double y = (alpha * sigma2 + x) * invert_sqrt2sigma;

  const double v = 0.5 * beta * (beta * sigma2 - 2. * x);
  const double z = (beta * sigma2 - x) * invert_sqrt2sigma;

  // 2. Calculate

  const double erfcy = gsl_sf_erfc(y);
  double part1(0.);
  if (fabs(erfcy) > DBL_MIN)
    part1 = exp(u) * erfcy;

  const double erfcz = gsl_sf_erfc(z);
  double part2(0.);
  if (fabs(erfcz) > DBL_MIN)
    part2 = exp(v) * erfcz;

  const double omega1 = (1. - eta) * N * (part1 + part2);
  double omega2(0.);
  if (eta >= 1.0E-8) {
    const double SQRT_H_5 = sqrt(H) * .5;
    std::complex<double> p(alpha * x, alpha * SQRT_H_5);
    std::complex<double> q(-beta * x, beta * SQRT_H_5);
    double omega2a = imag(exp(p) * Mantid::API::E1(p));
    double omega2b = imag(exp(q) * Mantid::API::E1(q));
    omega2 = -1.0 * N * eta * (omega2a + omega2b) * M_2_PI;
  }
  const double omega = omega1 + omega2;

  if (explicitoutput) {
    if (omega <= NEG_DBL_MAX || omega >= DBL_MAX) {
      stringstream errss;
      errss << "Find omega = " << omega << " is infinity! omega1 = " << omega1 << ", omega2 = " << omega2 << "\n";
      errss << "  u = " << u << ", v = " << v << ", erfc(y) = " << gsl_sf_erfc(y) << ", erfc(z) = " << gsl_sf_erfc(z)
            << "\n";
      errss << "  alpha = " << alpha << ", x = " << x << " sigma2 = " << sigma2 << ", N = " << N << "\n";
      g_log.warning(errss.str());
    }
  }

  // cout << "[DB] Final Value = " << omega << '\n';
  return omega;
}

//----------------------------------------------------------------------------------------------
/** Override setting parameter by parameter index
 */
void ThermalNeutronBk2BkExpConvPVoigt::setParameter(size_t i, const double &value, bool explicitlySet) {
  if (i == LATTICEINDEX) {
    // Lattice parameter
    if (fabs(m_unitCellSize - value) > 1.0E-8) {
      // If change in value is non-trivial
      m_cellParamValueChanged = true;
      ParamFunction::setParameter(i, value, explicitlySet);
      m_hasNewParameterValue = true;
      m_unitCellSize = value;
    }
  } else {
    // Non lattice parameter
    ParamFunction::setParameter(i, value, explicitlySet);
    m_hasNewParameterValue = true;
  }
}

//----------------------------------------------------------------------------------------------
/** Overriding setting parameter by parameter name
 */
void ThermalNeutronBk2BkExpConvPVoigt::setParameter(const std::string &name, const double &value, bool explicitlySet) {
  if (name == "LatticeConstant") {
    // Lattice parameter
    if (fabs(m_unitCellSize - value) > 1.0E-8) {
      // If change in value is non-trivial
      m_cellParamValueChanged = true;
      ParamFunction::setParameter(LATTICEINDEX, value, explicitlySet);
      m_hasNewParameterValue = true;
      m_unitCellSize = value;
    }
  } else {
    ParamFunction::setParameter(name, value, explicitlySet);
    m_hasNewParameterValue = true;
  }
}

//----------------------------------------------------------------------------------------------
/** This is called during long-running operations,
 * and check if the algorithm has requested that it be cancelled.
void ThermalNeutronBk2BkExpConvPVoigt::interruption_point() const
{
  // only throw exceptions if the code is not multi threaded otherwise you
contravene the OpenMP standard
  // that defines that all loops must complete, and no exception can leave an
OpenMP section
  // openmp cancel handling is performed using the ??, ?? and ?? macros in each
algrothim
  IF_NOT_PARALLEL
      if (m_cancel) throw Algorithm::CancelException();
}
*/

//-------------------------  External Functions
//---------------------------------------------------
/** Implementation of complex integral E_1
std::complex<double> E1X(std::complex<double> z)
{


  std::complex<double> exp_e1;

  double rz = real(z);
  double az = abs(z);

  if (fabs(az) < 1.0E-8)
  {
    // If z = 0, then the result is infinity... diverge!
    complex<double> r(1.0E300, 0.0);
    exp_e1 = r;
  }
  else if (az <= 10.0 || (rz < 0.0 && az < 20.0))
  {
    // Some interesting region, equal to integrate to infinity, converged

    complex<double> r(1.0, 0.0);
    exp_e1 = r;
    complex<double> cr = r;

    for (size_t k = 1; k <= 150; ++k)
    {
      double dk = double(k);
      cr = -cr * dk * z / ( (dk+1.0)*(dk+1.0) );
      exp_e1 += cr;
      if (abs(cr) < abs(exp_e1)*1.0E-15)
      {
        // cr is converged to zero
        break;
      }
    } // ENDFOR k

    const double el = 0.5772156649015328;
    exp_e1 = -el - log(z) + (z*exp_e1);
  }
  else
  {
    // Rest of the region
    complex<double> ct0(0.0, 0.0);
    for (int k = 120; k > 0; --k)
    {
      complex<double> dk(double(k), 0.0);
      ct0 = dk / (10.0 + dk / (z + ct0));
    } // ENDFOR k

    exp_e1 = 1.0 / (z + ct0);
    exp_e1 = exp_e1 * exp(-z);
    if (rz < 0.0 && fabs(imag(z)) < 1.0E-10 )
    {
      complex<double> u(0.0, 1.0);
      exp_e1 = exp_e1 - (M_PI * u);
    }
  }


  return exp_e1;
}
   */

//----------------------------------------------------------------------------------------------
/** (Migrated from IPeakFunction)
 * General implementation of the method for all peaks. Limits the peak
 * evaluation to
 * a certain number of FWHMs around the peak centre. The outside points are set
 * to 0.
 * Calls functionLocal() to compute the actual values
 * @param out :: Output function values
 * @param xValues :: X values for data points
 * @param nData :: Number of data points
 */
void ThermalNeutronBk2BkExpConvPVoigt::function1D(double *out, const double *xValues, const size_t nData) const {
  double c = centre();
  double dx = fabs(s_peakRadius * this->fwhm());
  int i0 = -1;
  int n = 0;
  for (size_t i = 0; i < nData; ++i) {
    if (fabs(xValues[i] - c) < dx) {
      if (i0 < 0)
        i0 = static_cast<int>(i);
      ++n;
    } else {
      out[i] = 0.0;
    }
  }
  if (i0 < 0 || n == 0)
    return;
  this->functionLocal(out + i0, xValues + i0, n);
}

/// Default value for the peak radius
int ThermalNeutronBk2BkExpConvPVoigt::s_peakRadius = 5;

//----------------------------------------------------------------------------------------------
/** Set peak radius

void ThermalNeutronBk2BkExpConvPVoigt::setPeakRadius(const int& r)
{
  if (r > 0)
  {
    s_peakRadius = r;
    std::string setting = boost::lexical_cast<std::string>(r);
    Kernel::ConfigService::Instance().setString("curvefitting.peakRadius",setting);
  }
}
  */

} // namespace Mantid::CurveFitting::Functions