void ModeratorTzero::execEvent(const std::string &emode) {
  g_log.information("Processing event workspace");

  const MatrixWorkspace_const_sptr matrixInputWS =
      getProperty("InputWorkspace");
  EventWorkspace_const_sptr inputWS =
      boost::dynamic_pointer_cast<const EventWorkspace>(matrixInputWS);

  // generate the output workspace pointer
  const size_t numHists = static_cast<size_t>(inputWS->getNumberHistograms());
  Mantid::API::MatrixWorkspace_sptr matrixOutputWS =
      getProperty("OutputWorkspace");
  EventWorkspace_sptr outputWS;
  if (matrixOutputWS == matrixInputWS) {
    outputWS = boost::dynamic_pointer_cast<EventWorkspace>(matrixOutputWS);
  } else {
    // Make a brand new EventWorkspace
    outputWS = boost::dynamic_pointer_cast<EventWorkspace>(
        WorkspaceFactory::Instance().create("EventWorkspace", numHists, 2, 1));
    // Copy geometry over.
    WorkspaceFactory::Instance().initializeFromParent(inputWS, outputWS, false);
    // You need to copy over the data as well.
    outputWS->copyDataFrom((*inputWS));
    // Cast to the matrixOutputWS and save it
    matrixOutputWS = boost::dynamic_pointer_cast<MatrixWorkspace>(outputWS);
    setProperty("OutputWorkspace", matrixOutputWS);
  }

  // Get pointers to sample and source
  IComponent_const_sptr source = m_instrument->getSource();
  IComponent_const_sptr sample = m_instrument->getSample();
  double Lss = source->getDistance(*sample); // distance from source to sample

  // calculate tof shift once for all neutrons if emode==Direct
  double t0_direct(-1);
  if (emode == "Direct") {
    Kernel::Property *eiprop = inputWS->run().getProperty("Ei");
    double Ei = boost::lexical_cast<double>(eiprop->value());
    mu::Parser parser;
    parser.DefineVar("incidentEnergy", &Ei); // associate E1 to this parser
    parser.SetExpr(m_formula);
    t0_direct = parser.Eval();
  }

  // Loop over the spectra
  Progress prog(this, 0.0, 1.0, numHists); // report progress of algorithm
  PARALLEL_FOR1(outputWS)
  for (int i = 0; i < static_cast<int>(numHists); ++i) {
    PARALLEL_START_INTERUPT_REGION
    size_t wsIndex = static_cast<size_t>(i);
    EventList &evlist = outputWS->getEventList(wsIndex);
    if (evlist.getNumberEvents() > 0) // don't bother with empty lists
    {
      IDetector_const_sptr det;
      double L1(Lss); // distance from source to sample
      double L2(-1);  // distance from sample to detector

      try {
        det = inputWS->getDetector(i);
        if (det->isMonitor()) {
          // redefine the sample as the monitor
          L1 = source->getDistance(*det);
          L2 = 0;
        } else {
          L2 = sample->getDistance(*det);
        }
      } catch (Exception::NotFoundError &) {
        g_log.error() << "Unable to calculate distances to/from detector" << i
                      << std::endl;
      }

      if (L2 >= 0) {
        // One parser for each parallel processor needed (except Edirect mode)
        double E1;
        mu::Parser parser;
        parser.DefineVar("incidentEnergy", &E1); // associate E1 to this parser
        parser.SetExpr(m_formula);

        // fast neutrons are shifted by min_t0_next, irrespective of tof
        double v1_max = L1 / m_t1min;
        E1 = m_convfactor * v1_max * v1_max;
        double min_t0_next = parser.Eval();

        if (emode == "Indirect") {
          double t2(-1.0); // time from sample to detector. (-1) signals error
          if (det->isMonitor()) {
            t2 = 0.0;
          } else {
            static const double convFact =
                1.0e-6 * sqrt(2 * PhysicalConstants::meV /
                              PhysicalConstants::NeutronMass);
            std::vector<double> wsProp = det->getNumberParameter("Efixed");
            if (!wsProp.empty()) {
              double E2 = wsProp.at(0);        //[E2]=meV
              double v2 = convFact * sqrt(E2); //[v2]=meter/microsec
              t2 = L2 / v2;
            } else {
              // t2 is kept to -1 if no Efixed is found
              g_log.debug() << "Efixed not found for detector " << i
                            << std::endl;
            }
          }
          if (t2 >= 0) // t2 < 0 when no detector info is available
          {
            // fix the histogram bins
            MantidVec &x = evlist.dataX();
            for (double &tof : x) {
              if (tof < m_t1min + t2)
                tof -= min_t0_next;
              else
                tof -= CalculateT0indirect(tof, L1, t2, E1, parser);
            }

            MantidVec tofs = evlist.getTofs();
            for (double &tof : tofs) {
              if (tof < m_t1min + t2)
                tof -= min_t0_next;
              else
                tof -= CalculateT0indirect(tof, L1, t2, E1, parser);
            }
            evlist.setTofs(tofs);
            evlist.setSortOrder(Mantid::DataObjects::EventSortType::UNSORTED);
          } // end of if( t2>= 0)
        }   // end of if(emode=="Indirect")
        else if (emode == "Elastic") {
          // Apply t0 correction to histogram bins
          MantidVec &x = evlist.dataX();
          for (double &tof : x) {
            if (tof < m_t1min * (L1 + L2) / L1)
              tof -= min_t0_next;
            else
              tof -= CalculateT0elastic(tof, L1 + L2, E1, parser);
          }

          MantidVec tofs = evlist.getTofs();
          for (double &tof : tofs) {
            // add a [-0.1,0.1] microsecond noise to avoid artifacts
            // resulting from original tof data
            if (tof < m_t1min * (L1 + L2) / L1)
              tof -= min_t0_next;
            else
              tof -= CalculateT0elastic(tof, L1 + L2, E1, parser);
          }
          evlist.setTofs(tofs);
          evlist.setSortOrder(Mantid::DataObjects::EventSortType::UNSORTED);

          MantidVec tofs_b = evlist.getTofs();
          MantidVec xarray = evlist.readX();
        } // end of else if(emode=="Elastic")
        else if (emode == "Direct") {
          // fix the histogram bins
          MantidVec &x = evlist.dataX();
          for (double &tof : x) {
            tof -= t0_direct;
          }

          MantidVec tofs = evlist.getTofs();
          for (double &tof : tofs) {
            tof -= t0_direct;
          }
          evlist.setTofs(tofs);
          evlist.setSortOrder(Mantid::DataObjects::EventSortType::UNSORTED);
        } // end of else if(emode=="Direct")
      }   // end of if(L2 >= 0)
    }     // end of if (evlist.getNumberEvents() > 0)
    prog.report();
    PARALLEL_END_INTERUPT_REGION
  } // end of for (int i = 0; i < static_cast<int>(numHists); ++i)
  PARALLEL_CHECK_INTERUPT_REGION
  outputWS->clearMRU(); // Clears the Most Recent Used lists */
} // end of void ModeratorTzero::execEvent()
void ModeratorTzero::execEvent(const std::string &emode) {
  g_log.information("Processing event workspace");

  const MatrixWorkspace_const_sptr matrixInputWS =
      getProperty("InputWorkspace");

  // generate the output workspace pointer
  API::MatrixWorkspace_sptr matrixOutputWS = getProperty("OutputWorkspace");
  if (matrixOutputWS != matrixInputWS) {
    matrixOutputWS = matrixInputWS->clone();
    setProperty("OutputWorkspace", matrixOutputWS);
  }
  auto outputWS = boost::dynamic_pointer_cast<EventWorkspace>(matrixOutputWS);

  // calculate tof shift once for all neutrons if emode==Direct
  double t0_direct(-1);
  if (emode == "Direct") {
    Kernel::Property *eiprop = outputWS->run().getProperty("Ei");
    double Ei = boost::lexical_cast<double>(eiprop->value());
    mu::Parser parser;
    parser.DefineVar("incidentEnergy", &Ei); // associate E1 to this parser
    parser.SetExpr(m_formula);
    t0_direct = parser.Eval();
  }

  const auto &spectrumInfo = outputWS->spectrumInfo();
  const double Lss = spectrumInfo.l1();

  // Loop over the spectra
  const size_t numHists = static_cast<size_t>(outputWS->getNumberHistograms());
  Progress prog(this, 0.0, 1.0, numHists); // report progress of algorithm
  PARALLEL_FOR_IF(Kernel::threadSafe(*outputWS))
  for (int i = 0; i < static_cast<int>(numHists); ++i) {
    PARALLEL_START_INTERUPT_REGION
    size_t wsIndex = static_cast<size_t>(i);
    EventList &evlist = outputWS->getSpectrum(wsIndex);
    if (evlist.getNumberEvents() > 0) // don't bother with empty lists
    {
      double L1(Lss); // distance from source to sample
      double L2(-1);  // distance from sample to detector

      if (spectrumInfo.hasDetectors(i)) {
        if (spectrumInfo.isMonitor(i)) {
          // redefine the sample as the monitor
          L1 = Lss + spectrumInfo.l2(i); // L2 in SpectrumInfo defined negative
          L2 = 0;
        } else {
          L2 = spectrumInfo.l2(i);
        }
      } else {
        g_log.error() << "Unable to calculate distances to/from detector" << i
                      << '\n';
      }

      if (L2 >= 0) {
        // One parser for each parallel processor needed (except Edirect mode)
        double E1;
        mu::Parser parser;
        parser.DefineVar("incidentEnergy", &E1); // associate E1 to this parser
        parser.SetExpr(m_formula);

        // fast neutrons are shifted by min_t0_next, irrespective of tof
        double v1_max = L1 / m_t1min;
        E1 = m_convfactor * v1_max * v1_max;
        double min_t0_next = parser.Eval();

        if (emode == "Indirect") {
          double t2(-1.0); // time from sample to detector. (-1) signals error
          if (spectrumInfo.isMonitor(i)) {
            t2 = 0.0;
          } else {
            static const double convFact =
                1.0e-6 * sqrt(2 * PhysicalConstants::meV /
                              PhysicalConstants::NeutronMass);
            std::vector<double> wsProp =
                spectrumInfo.detector(i).getNumberParameter("Efixed");
            if (!wsProp.empty()) {
              double E2 = wsProp.at(0);        //[E2]=meV
              double v2 = convFact * sqrt(E2); //[v2]=meter/microsec
              t2 = L2 / v2;
            } else {
              // t2 is kept to -1 if no Efixed is found
              g_log.debug() << "Efixed not found for detector " << i << '\n';
            }
          }
          if (t2 >= 0) // t2 < 0 when no detector info is available
          {
            // fix the histogram bins
            auto &x = evlist.mutableX();
            for (double &tof : x) {
              if (tof < m_t1min + t2)
                tof -= min_t0_next;
              else
                tof -= CalculateT0indirect(tof, L1, t2, E1, parser);
            }

            MantidVec tofs = evlist.getTofs();
            for (double &tof : tofs) {
              if (tof < m_t1min + t2)
                tof -= min_t0_next;
              else
                tof -= CalculateT0indirect(tof, L1, t2, E1, parser);
            }
            evlist.setTofs(tofs);
            evlist.setSortOrder(Mantid::DataObjects::EventSortType::UNSORTED);
          } // end of if( t2>= 0)
        }   // end of if(emode=="Indirect")
        else if (emode == "Elastic") {
          // Apply t0 correction to histogram bins
          auto &x = evlist.mutableX();
          for (double &tof : x) {
            if (tof < m_t1min * (L1 + L2) / L1)
              tof -= min_t0_next;
            else
              tof -= CalculateT0elastic(tof, L1 + L2, E1, parser);
          }

          MantidVec tofs = evlist.getTofs();
          for (double &tof : tofs) {
            // add a [-0.1,0.1] microsecond noise to avoid artifacts
            // resulting from original tof data
            if (tof < m_t1min * (L1 + L2) / L1)
              tof -= min_t0_next;
            else
              tof -= CalculateT0elastic(tof, L1 + L2, E1, parser);
          }
          evlist.setTofs(tofs);
          evlist.setSortOrder(Mantid::DataObjects::EventSortType::UNSORTED);
        } // end of else if(emode=="Elastic")
        else if (emode == "Direct") {
          // fix the histogram bins
          evlist.mutableX() -= t0_direct;

          MantidVec tofs = evlist.getTofs();
          for (double &tof : tofs) {
            tof -= t0_direct;
          }
          evlist.setTofs(tofs);
          evlist.setSortOrder(Mantid::DataObjects::EventSortType::UNSORTED);
        } // end of else if(emode=="Direct")
      }   // end of if(L2 >= 0)
    }     // end of if (evlist.getNumberEvents() > 0)
    prog.report();
    PARALLEL_END_INTERUPT_REGION
  } // end of for (int i = 0; i < static_cast<int>(numHists); ++i)
  PARALLEL_CHECK_INTERUPT_REGION
  outputWS->clearMRU(); // Clears the Most Recent Used lists */
} // end of void ModeratorTzero::execEvent()