SassenaFFT.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 +
//----------------------------------------------------------------------
// Includes
//----------------------------------------------------------------------
#include "MantidAlgorithms/SassenaFFT.h"

#include "MantidAPI/Axis.h"
#include "MantidAPI/FileProperty.h"
#include "MantidAPI/IAlgorithm.h"
#include "MantidAPI/MatrixWorkspace.h"
#include "MantidAPI/WorkspaceGroup.h"
#include "MantidDataObjects/Workspace2D.h"
#include "MantidKernel/EnabledWhenProperty.h"
#include "MantidKernel/UnitFactory.h"

namespace Mantid {
namespace Algorithms {

// Register the class into the algorithm factory
DECLARE_ALGORITHM(SassenaFFT)

/// Override Algorithm::checkGroups
bool SassenaFFT::checkGroups() { return false; }

/// processGroups must not be called
bool SassenaFFT::processGroups() {
  const std::string errMessg = "processGroups must not be called from SassenaFFT";
  this->g_log.error(errMessg);
  throw std::logic_error(errMessg);
  return false;
}

/**
 * Initialise the algorithm. Declare properties which can be set before
 * execution (input) or
 * read from after the execution (output).
 */
void SassenaFFT::init() {
  this->declareProperty(
      std::make_unique<API::WorkspaceProperty<API::WorkspaceGroup>>("InputWorkspace", "", Kernel::Direction::InOut),
      "The name of the input group workspace");
  // properties for the detailed balance condition
  this->declareProperty(
      std::make_unique<Kernel::PropertyWithValue<bool>>("FFTonlyRealPart", false, Kernel::Direction::Input),
      "Do we FFT only the real part of I(Q,t)? (optional, default is False)");
  this->declareProperty(
      std::make_unique<Kernel::PropertyWithValue<bool>>("DetailedBalance", false, Kernel::Direction::Input),
      "Do we apply detailed balance condition? (optional, default is False)");
  this->declareProperty("Temp", 300.0, "Multiply structure factor by exp(E/(2*kT)");
  this->setPropertySettings("Temp",
                            std::make_unique<Kernel::EnabledWhenProperty>("DetailedBalance", Kernel::IS_EQUAL_TO, "1"));
}

/// Execute the algorithm
void SassenaFFT::exec() {
  const std::string gwsName = this->getPropertyValue("InputWorkspace");
  API::WorkspaceGroup_sptr gws = this->getProperty("InputWorkspace");

  const std::string ftqReName = gwsName + "_fqt.Re";
  const std::string ftqImName = gwsName + "_fqt.Im";

  // Make sure the intermediate structure factor is there
  if (!gws->contains(ftqReName)) {
    const std::string errMessg = "workspace " + gwsName + " does not contain an intermediate structure factor";
    this->g_log.error(errMessg);
    throw Kernel::Exception::NotFoundError("group workspace does not contain", ftqReName);
  }

  // Retrieve the real and imaginary parts of the intermediate scattering
  // function
  DataObjects::Workspace2D_sptr fqtRe = std::dynamic_pointer_cast<DataObjects::Workspace2D>(gws->getItem(ftqReName));
  DataObjects::Workspace2D_sptr fqtIm = std::dynamic_pointer_cast<DataObjects::Workspace2D>(gws->getItem(ftqImName));

  // Calculate the FFT for all spectra, retaining only the real part since
  // F(q,-t) = F*(q,t)
  int part = 3; // extract the real part of the transform, assuming I(Q,t) is real
  const std::string sqwName = gwsName + "_sqw";
  API::IAlgorithm_sptr fft = this->createChildAlgorithm("ExtractFFTSpectrum");
  fft->setProperty<DataObjects::Workspace2D_sptr>("InputWorkspace", fqtRe);
  if (!this->getProperty("FFTonlyRealPart")) {
    part = 0; // extract the real part of the transform, assuming I(Q,t) is complex
    fft->setProperty<DataObjects::Workspace2D_sptr>("InputImagWorkspace", fqtIm);
  }
  fft->setPropertyValue("OutputWorkspace", sqwName);
  fft->setProperty<int>("FFTPart", part); // extract the real part
  fft->executeAsChildAlg();
  API::MatrixWorkspace_sptr sqw0 = fft->getProperty("OutputWorkspace");
  DataObjects::Workspace2D_sptr sqw = std::dynamic_pointer_cast<DataObjects::Workspace2D>(sqw0);
  API::AnalysisDataService::Instance().addOrReplace(sqwName, sqw);

  // Transform the X-axis to appropriate dimensions
  // We assume the units of the intermediate scattering function are in
  // picoseconds
  // The resulting frequency unit is in mili-eV, thus use m_ps2meV
  API::IAlgorithm_sptr scaleX = this->createChildAlgorithm("ScaleX");
  scaleX->setProperty<DataObjects::Workspace2D_sptr>("InputWorkspace", sqw);
  scaleX->setProperty<double>("Factor", m_ps2meV);
  scaleX->setProperty<DataObjects::Workspace2D_sptr>("OutputWorkspace", sqw);
  scaleX->executeAsChildAlg();

  // Do we apply the detailed balance condition exp(E/(2*kT)) ?
  if (this->getProperty("DetailedBalance")) {
    double T = this->getProperty("Temp");
    // The ExponentialCorrection algorithm assumes the form C0*exp(-C1*x). Note
    // the explicit minus in the exponent
    API::IAlgorithm_sptr ec = this->createChildAlgorithm("ExponentialCorrection");
    ec->setProperty<DataObjects::Workspace2D_sptr>("InputWorkspace", sqw);
    ec->setProperty<DataObjects::Workspace2D_sptr>("OutputWorkspace", sqw);
    ec->setProperty<double>("C0", 1.0);
    ec->setProperty<double>("C1", -1.0 / (2.0 * T * m_T2ueV)); // Temperature in units of ueV
    ec->setPropertyValue("Operation", "Multiply");
    ec->executeAsChildAlg();
  }

  // Set the Energy unit for the X-axis
  sqw->getAxis(0)->unit() = Kernel::UnitFactory::Instance().create("DeltaE");

  // Add to group workspace, except if we are replacing the workspace. In this
  // case, the group workspace
  // is already notified of the changes by the analysis data service.
  if (!gws->contains(sqwName)) {
    gws->add(sqwName);
  } else {
    this->g_log.information("Workspace " + sqwName + " replaced with new contents");
  }
}

} // namespace Algorithms
} // namespace Mantid