AlphaCalc.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 "MantidMuon/AlphaCalc.h"
#include "MantidAPI/MatrixWorkspace.h"
#include "MantidKernel/ArrayProperty.h"

#include <cmath>
#include <vector>

namespace Mantid::Algorithms {

using namespace Kernel;

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

/** Initialisation method. Declares properties to be used in algorithm.
 *
 */
void AlphaCalc::init() {

  declareProperty(std::make_unique<API::WorkspaceProperty<>>("InputWorkspace", "", Direction::Input),
                  "Name of the input workspace");

  std::vector<int> forwardDefault{1};
  declareProperty(std::make_unique<ArrayProperty<int>>("ForwardSpectra", std::move(forwardDefault)),
                  "The spectra numbers of the forward group (default to 1)");

  std::vector<int> backwardDefault{2};
  declareProperty(std::make_unique<ArrayProperty<int>>("BackwardSpectra", std::move(backwardDefault)),
                  "The spectra numbers of the backward group (default to 2)");

  declareProperty("FirstGoodValue", EMPTY_DBL(), "First good value (default lowest value of x)", Direction::Input);
  declareProperty("LastGoodValue", EMPTY_DBL(), "Last good value (default highest value of x)", Direction::Input);

  declareProperty("Alpha", 1.0, "The alpha efficiency (default to 1.0)", Direction::Output);
}

/** Executes the algorithm
 *
 */
void AlphaCalc::exec() {
  std::vector<int> forwardSpectraList = getProperty("ForwardSpectra");
  std::vector<int> backwardSpectraList = getProperty("BackwardSpectra");

  double alpha = getProperty("Alpha");

  // no point in attempting to calculate alpha if input workspace on contains
  // one spectra
  API::MatrixWorkspace_sptr inputWS = getProperty("InputWorkspace");
  if (inputWS->getNumberHistograms() < 2) {
    g_log.error() << "Can't calculate alpha value for workspace which"
                  << " contains one spectrum. A default value of alpha = 1.0 is returned";
    setProperty("Alpha", alpha);
    return;
  }

  // if for some reason the size of forward and backward lists are zero
  // default these to their defaults
  if (forwardSpectraList.empty())
    forwardSpectraList.emplace_back(1);
  if (backwardSpectraList.empty())
    backwardSpectraList.emplace_back(2);

  // first step is to create two workspaces which groups all forward and
  // backward spectra

  auto groupForward = createChildAlgorithm("GroupDetectors");
  groupForward->setProperty("InputWorkspace", inputWS);
  groupForward->setProperty("OutputWorkspace", "tmp");
  groupForward->setProperty("SpectraList", forwardSpectraList);
  groupForward->setProperty("KeepUngroupedSpectra", false);
  groupForward->execute();
  API::MatrixWorkspace_sptr forwardWS = groupForward->getProperty("OutputWorkspace");

  auto groupBackward = createChildAlgorithm("GroupDetectors");
  groupBackward->setProperty("InputWorkspace", inputWS);
  groupBackward->setProperty("OutputWorkspace", "tmp");
  groupBackward->setProperty("SpectraList", backwardSpectraList);
  groupBackward->setProperty("KeepUngroupedSpectra", false);
  groupBackward->execute();
  API::MatrixWorkspace_sptr backwardWS = groupBackward->getProperty("OutputWorkspace");

  // calculate sum of forward counts

  double firstGoodvalue = getProperty("FirstGoodValue");
  double lastGoodvalue = getProperty("LastGoodValue");

  auto integr = createChildAlgorithm("Integration");
  integr->setProperty("InputWorkspace", forwardWS);
  integr->setPropertyValue("OutputWorkspace", "tmp");
  if (firstGoodvalue != EMPTY_DBL())
    integr->setProperty("RangeLower", firstGoodvalue);
  if (lastGoodvalue != EMPTY_DBL())
    integr->setProperty("RangeUpper", lastGoodvalue);
  integr->execute();
  API::MatrixWorkspace_sptr out = integr->getProperty("OutputWorkspace");

  double sumForward = out->readY(0)[0];

  if (sumForward < 0) {
    g_log.error() << "Sum of forward detector counts is negative."
                  << "Therefore can't calculate alpha. Return alpha = 1.0.";
    setProperty("Alpha", alpha);
    return;
  }

  // calculate sum of backward counts

  auto integrB = createChildAlgorithm("Integration");
  integrB->setProperty("InputWorkspace", backwardWS);
  integrB->setPropertyValue("OutputWorkspace", "tmp");
  if (firstGoodvalue != EMPTY_DBL())
    integrB->setProperty("RangeLower", firstGoodvalue);
  if (lastGoodvalue != EMPTY_DBL())
    integrB->setProperty("RangeUpper", lastGoodvalue);
  integrB->execute();
  out = integrB->getProperty("OutputWorkspace");

  double sumBackward = out->readY(0)[0];

  if (sumBackward <= 0) {
    g_log.error() << "Sum of backward detector counts is negative or zero."
                  << "Therefore can't calculate alpha. Return alpha = 1.0.";
    setProperty("Alpha", alpha);
    return;
  }

  // finally calculate alpha

  setProperty("Alpha", sumForward / sumBackward);
}

} // namespace Mantid::Algorithms