LoadEventNexus.cpp

#include "MantidDataHandling/LoadEventNexus.h"
#include "MantidDataHandling/LoadEventNexusIndexSetup.h"
#include "MantidDataHandling/EventWorkspaceCollection.h"
#include "MantidDataHandling/DefaultEventLoader.h"
#include "MantidDataHandling/ParallelEventLoader.h"
#include "MantidAPI/Axis.h"
#include "MantidAPI/FileProperty.h"
#include "MantidAPI/RegisterFileLoader.h"
#include "MantidAPI/Run.h"
#include "MantidAPI/Sample.h"
#include "MantidGeometry/Instrument.h"
#include "MantidGeometry/Instrument/Goniometer.h"
#include "MantidGeometry/Instrument/RectangularDetector.h"
#include "MantidKernel/ArrayProperty.h"
#include "MantidKernel/BoundedValidator.h"
#include "MantidKernel/DateAndTimeHelpers.h"
#include "MantidKernel/ListValidator.h"
#include "MantidKernel/MultiThreaded.h"
#include "MantidKernel/TimeSeriesProperty.h"
#include "MantidKernel/Timer.h"
#include "MantidKernel/UnitFactory.h"
#include "MantidKernel/VisibleWhenProperty.h"
#include "MantidIndexing/IndexInfo.h"

#include <boost/function.hpp>
#include <boost/shared_array.hpp>
#include <boost/shared_ptr.hpp>

using Mantid::Types::Core::DateAndTime;
using Mantid::Types::Event::TofEvent;
using std::map;
using std::string;
using std::vector;
using namespace ::NeXus;

namespace Mantid {
namespace DataHandling {

DECLARE_NEXUS_FILELOADER_ALGORITHM(LoadEventNexus)

using namespace Kernel;
using namespace DateAndTimeHelpers;
using namespace Geometry;
using namespace API;
using namespace DataObjects;
using Types::Core::DateAndTime;
using Types::Event::TofEvent;

//----------------------------------------------------------------------------------------------
/** Empty default constructor
*/
LoadEventNexus::LoadEventNexus()
    : filter_tof_min(0), filter_tof_max(0), m_specMin(0), m_specMax(0),
      longest_tof(0), shortest_tof(0), bad_tofs(0), discarded_events(0),
      compressTolerance(0), m_instrument_loaded_correctly(false),
      loadlogs(false), m_logs_loaded_correctly(false), event_id_is_spec(false) {
}

//----------------------------------------------------------------------------------------------
/**
* Return the confidence with with this algorithm can load the file
* @param descriptor A descriptor for the file
* @returns An integer specifying the confidence level. 0 indicates it will not
* be used
*/
int LoadEventNexus::confidence(Kernel::NexusDescriptor &descriptor) const {
  int confidence(0);
  if (descriptor.classTypeExists("NXevent_data")) {
    if (descriptor.pathOfTypeExists("/entry", "NXentry") ||
        descriptor.pathOfTypeExists("/raw_data_1", "NXentry")) {
      confidence = 80;
    }
  }
  return confidence;
}

//----------------------------------------------------------------------------------------------
/** Initialisation method.
*/
void LoadEventNexus::init() {
  const std::vector<std::string> exts{"_event.nxs", ".nxs.h5", ".nxs"};
  this->declareProperty(
      Kernel::make_unique<FileProperty>("Filename", "", FileProperty::Load,
                                        exts),
      "The name of the Event NeXus file to read, including its full or "
      "relative path. "
      "The file name is typically of the form INST_####_event.nxs (N.B. case "
      "sensitive if running on Linux).");

  this->declareProperty(
      make_unique<WorkspaceProperty<Workspace>>("OutputWorkspace", "",
                                                Direction::Output),
      "The name of the output EventWorkspace or WorkspaceGroup in which to "
      "load the EventNexus file.");

  declareProperty(
      make_unique<PropertyWithValue<string>>("NXentryName", "",
                                             Direction::Input),
      "Optional: Name of the NXentry to load if it's not the default.");

  declareProperty(make_unique<PropertyWithValue<double>>(
                      "FilterByTofMin", EMPTY_DBL(), Direction::Input),
                  "Optional: To exclude events that do not fall within a range "
                  "of times-of-flight. "
                  "This is the minimum accepted value in microseconds. Keep "
                  "blank to load all events.");

  declareProperty(make_unique<PropertyWithValue<double>>(
                      "FilterByTofMax", EMPTY_DBL(), Direction::Input),
                  "Optional: To exclude events that do not fall within a range "
                  "of times-of-flight. "
                  "This is the maximum accepted value in microseconds. Keep "
                  "blank to load all events.");

  declareProperty(make_unique<PropertyWithValue<double>>(
                      "FilterByTimeStart", EMPTY_DBL(), Direction::Input),
                  "Optional: To only include events after the provided start "
                  "time, in seconds (relative to the start of the run).");

  declareProperty(make_unique<PropertyWithValue<double>>(
                      "FilterByTimeStop", EMPTY_DBL(), Direction::Input),
                  "Optional: To only include events before the provided stop "
                  "time, in seconds (relative to the start of the run).");

  std::string grp1 = "Filter Events";
  setPropertyGroup("FilterByTofMin", grp1);
  setPropertyGroup("FilterByTofMax", grp1);
  setPropertyGroup("FilterByTimeStart", grp1);
  setPropertyGroup("FilterByTimeStop", grp1);

  declareProperty(
      make_unique<ArrayProperty<string>>("BankName", Direction::Input),
      "Optional: To only include events from one bank. Any bank "
      "whose name does not match the given string will have no "
      "events.");

  declareProperty(make_unique<PropertyWithValue<bool>>("SingleBankPixelsOnly",
                                                       true, Direction::Input),
                  "Optional: Only applies if you specified a single bank to "
                  "load with BankName. "
                  "Only pixels in the specified bank will be created if true; "
                  "all of the instrument's pixels will be created otherwise.");
  setPropertySettings("SingleBankPixelsOnly", make_unique<VisibleWhenProperty>(
                                                  "BankName", IS_NOT_DEFAULT));

  std::string grp2 = "Loading a Single Bank";
  setPropertyGroup("BankName", grp2);
  setPropertyGroup("SingleBankPixelsOnly", grp2);

  declareProperty(
      make_unique<PropertyWithValue<bool>>("Precount", true, Direction::Input),
      "Pre-count the number of events in each pixel before allocating memory "
      "(optional, default True). "
      "This can significantly reduce memory use and memory fragmentation; it "
      "may also speed up loading.");

  declareProperty(make_unique<PropertyWithValue<double>>(
                      "CompressTolerance", -1.0, Direction::Input),
                  "Run CompressEvents while loading (optional, leave blank or "
                  "negative to not do). "
                  "This specified the tolerance to use (in microseconds) when "
                  "compressing.");

  auto mustBePositive = boost::make_shared<BoundedValidator<int>>();
  mustBePositive->setLower(1);
  declareProperty("ChunkNumber", EMPTY_INT(), mustBePositive,
                  "If loading the file by sections ('chunks'), this is the "
                  "section number of this execution of the algorithm.");
  declareProperty("TotalChunks", EMPTY_INT(), mustBePositive,
                  "If loading the file by sections ('chunks'), this is the "
                  "total number of sections.");
  // TotalChunks is only meaningful if ChunkNumber is set
  // Would be nice to be able to restrict ChunkNumber to be <= TotalChunks at
  // validation
  setPropertySettings("TotalChunks", make_unique<VisibleWhenProperty>(
                                         "ChunkNumber", IS_NOT_DEFAULT));

  std::string grp3 = "Reduce Memory Use";
  setPropertyGroup("Precount", grp3);
  setPropertyGroup("CompressTolerance", grp3);
  setPropertyGroup("ChunkNumber", grp3);
  setPropertyGroup("TotalChunks", grp3);

  declareProperty(make_unique<PropertyWithValue<bool>>("LoadMonitors", false,
                                                       Direction::Input),
                  "Load the monitors from the file (optional, default False).");

  std::vector<std::string> options{"", "Events", "Histogram"};
  declareProperty("MonitorsLoadOnly", "",
                  boost::make_shared<Kernel::StringListValidator>(options),
                  "If multiple repesentations exist, which one to load. "
                  "Default is to load the one that is present.");

  declareProperty(make_unique<PropertyWithValue<double>>(
                      "FilterMonByTofMin", EMPTY_DBL(), Direction::Input),
                  "Optional: To exclude events from monitors that do not fall "
                  "within a range of times-of-flight. "
                  "This is the minimum accepted value in microseconds.");

  declareProperty(make_unique<PropertyWithValue<double>>(
                      "FilterMonByTofMax", EMPTY_DBL(), Direction::Input),
                  "Optional: To exclude events from monitors that do not fall "
                  "within a range of times-of-flight. "
                  "This is the maximum accepted value in microseconds.");

  declareProperty(make_unique<PropertyWithValue<double>>(
                      "FilterMonByTimeStart", EMPTY_DBL(), Direction::Input),
                  "Optional: To only include events from monitors after the "
                  "provided start time, in seconds (relative to the start of "
                  "the run).");

  declareProperty(make_unique<PropertyWithValue<double>>(
                      "FilterMonByTimeStop", EMPTY_DBL(), Direction::Input),
                  "Optional: To only include events from monitors before the "
                  "provided stop time, in seconds (relative to the start of "
                  "the run).");

  setPropertySettings(
      "MonitorsLoadOnly",
      make_unique<VisibleWhenProperty>("LoadMonitors", IS_EQUAL_TO, "1"));
  auto asEventsIsOn = [] {
    std::unique_ptr<IPropertySettings> prop =
        make_unique<VisibleWhenProperty>("LoadMonitors", IS_EQUAL_TO, "1");
    return prop;
  };
  setPropertySettings("FilterMonByTofMin", asEventsIsOn());
  setPropertySettings("FilterMonByTofMax", asEventsIsOn());
  setPropertySettings("FilterMonByTimeStart", asEventsIsOn());
  setPropertySettings("FilterMonByTimeStop", asEventsIsOn());

  std::string grp4 = "Monitors";
  setPropertyGroup("LoadMonitors", grp4);
  setPropertyGroup("MonitorsLoadOnly", grp4);
  setPropertyGroup("FilterMonByTofMin", grp4);
  setPropertyGroup("FilterMonByTofMax", grp4);
  setPropertyGroup("FilterMonByTimeStart", grp4);
  setPropertyGroup("FilterMonByTimeStop", grp4);

  declareProperty("SpectrumMin", EMPTY_INT(), mustBePositive,
                  "The number of the first spectrum to read.");
  declareProperty("SpectrumMax", EMPTY_INT(), mustBePositive,
                  "The number of the last spectrum to read.");
  declareProperty(make_unique<ArrayProperty<int32_t>>("SpectrumList"),
                  "A comma-separated list of individual spectra to read.");

  declareProperty(
      make_unique<PropertyWithValue<bool>>("MetaDataOnly", false,
                                           Direction::Input),
      "If true, only the meta data and sample logs will be loaded.");

  declareProperty(
      make_unique<PropertyWithValue<bool>>("LoadLogs", true, Direction::Input),
      "Load the Sample/DAS logs from the file (default True).");

#ifdef MPI_EXPERIMENTAL
  declareProperty(make_unique<PropertyWithValue<bool>>("UseParallelLoader",
                                                       true, Direction::Input),
                  "Use experimental parallel loader for loading event data.");
#endif
}

//----------------------------------------------------------------------------------------------
/** set the name of the top level NXentry m_top_entry_name
*/
void LoadEventNexus::setTopEntryName() {
  std::string nxentryProperty = getProperty("NXentryName");
  if (!nxentryProperty.empty()) {
    m_top_entry_name = nxentryProperty;
    return;
  }
  using string_map_t = std::map<std::string, std::string>;
  try {
    string_map_t::const_iterator it;
    // assume we're at the top, otherwise: m_file->openPath("/");
    string_map_t entries = m_file->getEntries();

    // Choose the first entry as the default
    m_top_entry_name = entries.begin()->first;

    for (it = entries.begin(); it != entries.end(); ++it) {
      if (((it->first == "entry") || (it->first == "raw_data_1")) &&
          (it->second == "NXentry")) {
        m_top_entry_name = it->first;
        break;
      }
    }
  } catch (const std::exception &) {
    g_log.error() << "Unable to determine name of top level NXentry - assuming "
                     "\"entry\".\n";
    m_top_entry_name = "entry";
  }
}

template <typename T> void LoadEventNexus::filterDuringPause(T workspace) {
  try {
    if ((!ConfigService::Instance().hasProperty(
            "loadeventnexus.keeppausedevents")) &&
        (m_ws->run().getLogData("pause")->size() > 1)) {
      g_log.notice("Filtering out events when the run was marked as paused. "
                   "Set the loadeventnexus.keeppausedevents configuration "
                   "property to override this.");

      auto filter = createChildAlgorithm("FilterByLogValue");
      filter->setProperty("InputWorkspace", workspace);
      filter->setProperty("OutputWorkspace", workspace);
      filter->setProperty("LogName", "pause");
      // The log value is set to 1 when the run is paused, 0 otherwise.
      filter->setProperty("MinimumValue", 0.0);
      filter->setProperty("MaximumValue", 0.0);
      filter->setProperty("LogBoundary", "Left");
      filter->execute();
    }
  } catch (Exception::NotFoundError &) {
    // No "pause" log, just carry on
  }
}

template <>
void LoadEventNexus::filterDuringPause<EventWorkspaceCollection_sptr>(
    EventWorkspaceCollection_sptr workspace) {
  // We provide a function pointer to the filter method of the object
  boost::function<void(MatrixWorkspace_sptr)> func = std::bind1st(
      std::mem_fun(&LoadEventNexus::filterDuringPause<MatrixWorkspace_sptr>),
      this);
  workspace->applyFilter(func);
}

//------------------------------------------------------------------------------------------------
/** Executes the algorithm. Reading in the file and creating and populating
*  the output workspace
*/
void LoadEventNexus::exec() {
  // Retrieve the filename from the properties
  m_filename = getPropertyValue("Filename");

  compressTolerance = getProperty("CompressTolerance");

  loadlogs = getProperty("LoadLogs");

  // Check to see if the monitors need to be loaded later
  bool load_monitors = this->getProperty("LoadMonitors");

  // this must make absolutely sure that m_file is a valid (and open)
  // NeXus::File object
  safeOpenFile(m_filename);

  setTopEntryName();

  // Initialize progress reporting.
  int reports = 3;
  if (load_monitors)
    reports++;
  Progress prog(this, 0.0, 0.3, reports);

  // Load the detector events
  m_ws = boost::make_shared<EventWorkspaceCollection>(); // Algorithm currently
                                                         // relies on an
  // object-level workspace ptr
  loadEvents(&prog, false); // Do not load monitor blocks

  if (discarded_events > 0) {
    g_log.information() << discarded_events
                        << " events were encountered coming from pixels which "
                           "are not in the Instrument Definition File."
                           "These events were discarded.\n";
  }

  // If the run was paused at any point, filter out those events (SNS only, I
  // think)
  filterDuringPause(m_ws->getSingleHeldWorkspace());

  // add filename
  m_ws->mutableRun().addProperty("Filename", m_filename);
  // Save output
  this->setProperty("OutputWorkspace", m_ws->combinedWorkspace());

  // close the file since LoadNexusMonitors will take care of its own file
  // handle
  m_file->close();

  // Load the monitors with child algorithm 'LoadNexusMonitors'
  if (load_monitors) {
    prog.report("Loading monitors");
    this->runLoadMonitors();
  }
}

/**
* Get the number of events in the currently opened group.
*
* @param file The handle to the nexus file opened to the group to look at.
* @param hasTotalCounts Whether to try looking at the total_counts field. This
* variable will be changed if the field is not there.
* @param oldNeXusFileNames Whether to try using old names. This variable will
* be changed if it is determined that old names are being used.
*
* @return The number of events.
*/
std::size_t numEvents(::NeXus::File &file, bool &hasTotalCounts,
                      bool &oldNeXusFileNames) {
  // try getting the value of total_counts
  if (hasTotalCounts) {
    try {
      uint64_t numEvents;
      file.readData("total_counts", numEvents);
      return numEvents;
    } catch (::NeXus::Exception &) {
      hasTotalCounts = false; // carry on with the field not existing
    }
  }

  // just get the length of the event pixel ids
  try {
    if (oldNeXusFileNames)
      file.openData("event_pixel_id");
    else
      file.openData("event_id");
  } catch (::NeXus::Exception &) {
    // Older files (before Nov 5, 2010) used this field.
    try {
      file.openData("event_pixel_id");
      oldNeXusFileNames = true;
    } catch (::NeXus::Exception &) {
      // Some groups have neither indicating there are not events here
      return 0;
    }
  }

  size_t numEvents = static_cast<std::size_t>(file.getInfo().dims[0]);
  file.closeData();
  return numEvents;
}

/** Load the instrument from the nexus file
*
* @param nexusfilename :: The name of the nexus file being loaded
* @param localWorkspace :: Templated workspace in which to put the instrument
*geometry
* @param alg :: Handle of the algorithm
* @param returnpulsetimes :: flag to return shared pointer for BankPulseTimes,
*otherwise NULL.
* @param nPeriods : Number of periods (write to)
* @param periodLog : Period logs DateAndTime to int map.
*
* @return Pulse times given in the DAS logs
*/
template <typename T>
boost::shared_ptr<BankPulseTimes> LoadEventNexus::runLoadNexusLogs(
    const std::string &nexusfilename, T localWorkspace, API::Algorithm &alg,
    bool returnpulsetimes, int &nPeriods,
    std::unique_ptr<const TimeSeriesProperty<int>> &periodLog) {
  // --------------------- Load DAS Logs -----------------
  // The pulse times will be empty if not specified in the DAS logs.
  // BankPulseTimes * out = NULL;
  boost::shared_ptr<BankPulseTimes> out;
  API::IAlgorithm_sptr loadLogs = alg.createChildAlgorithm("LoadNexusLogs");

  // Now execute the Child Algorithm. Catch and log any error, but don't stop.
  try {
    alg.getLogger().information() << "Loading logs from NeXus file..."
                                  << "\n";
    loadLogs->setPropertyValue("Filename", nexusfilename);
    loadLogs->setProperty<API::MatrixWorkspace_sptr>("Workspace",
                                                     localWorkspace);
    try {
      loadLogs->setPropertyValue("NXentryName",
                                 alg.getPropertyValue("NXentryName"));
    } catch (...) {
    }

    loadLogs->execute();

    const Run &run = localWorkspace->run();
    // Get the number of periods
    if (run.hasProperty("nperiods")) {
      nPeriods = run.getPropertyValueAsType<int>("nperiods");
    }
    // Get the period log. Map of DateAndTime to Period int values.
    if (run.hasProperty("period_log")) {
      auto *temp = run.getProperty("period_log");
      periodLog.reset(dynamic_cast<TimeSeriesProperty<int> *>(temp->clone()));
    }

    // If successful, we can try to load the pulse times
    Kernel::TimeSeriesProperty<double> *log =
        dynamic_cast<Kernel::TimeSeriesProperty<double> *>(
            localWorkspace->mutableRun().getProperty("proton_charge"));
    std::vector<Types::Core::DateAndTime> temp;
    if (log)
      temp = log->timesAsVector();
    // if (returnpulsetimes) out = new BankPulseTimes(temp);
    if (returnpulsetimes)
      out = boost::make_shared<BankPulseTimes>(temp);

    // Use the first pulse as the run_start time.
    if (!temp.empty()) {
      if (temp[0] < Types::Core::DateAndTime("1991-01-01T00:00:00"))
        alg.getLogger().warning() << "Found entries in the proton_charge "
                                     "sample log with invalid pulse time!\n";

      Types::Core::DateAndTime run_start = localWorkspace->getFirstPulseTime();
      // add the start of the run as a ISO8601 date/time string. The start =
      // first non-zero time.
      // (this is used in LoadInstrument to find the right instrument file to
      // use).
      localWorkspace->mutableRun().addProperty(
          "run_start", run_start.toISO8601String(), true);
    } else {
      alg.getLogger().warning() << "Empty proton_charge sample log. You will "
                                   "not be able to filter by time.\n";
    }
    /// Attempt to make a gonoimeter from the logs
    try {
      Geometry::Goniometer gm;
      gm.makeUniversalGoniometer();
      localWorkspace->mutableRun().setGoniometer(gm, true);
    } catch (std::runtime_error &) {
    }
  } catch (...) {
    alg.getLogger().error() << "Error while loading Logs from SNS Nexus. Some "
                               "sample logs may be missing."
                            << "\n";
    return out;
  }
  return out;
}

/** Load the instrument from the nexus file
*
* @param nexusfilename :: The name of the nexus file being loaded
* @param localWorkspace :: EventWorkspaceCollection in which to put the
*instrument
*geometry
* @param alg :: Handle of the algorithm
* @param returnpulsetimes :: flag to return shared pointer for BankPulseTimes,
*otherwise NULL.
* @param nPeriods : Number of periods (write to)
* @param periodLog : Period logs DateAndTime to int map.
*
* @return Pulse times given in the DAS logs
*/
template <>
boost::shared_ptr<BankPulseTimes>
LoadEventNexus::runLoadNexusLogs<EventWorkspaceCollection_sptr>(
    const std::string &nexusfilename,
    EventWorkspaceCollection_sptr localWorkspace, API::Algorithm &alg,
    bool returnpulsetimes, int &nPeriods,
    std::unique_ptr<const TimeSeriesProperty<int>> &periodLog) {
  auto ws = localWorkspace->getSingleHeldWorkspace();
  auto ret = runLoadNexusLogs<MatrixWorkspace_sptr>(
      nexusfilename, ws, alg, returnpulsetimes, nPeriods, periodLog);
  return ret;
}

//-----------------------------------------------------------------------------
/**
* Load events from the file.
* @param prog :: A pointer to the progress reporting object
* @param monitors :: If true the events from the monitors are loaded and not the
* main banks
*
* This also loads the instrument, but only if it has not been set in the
*workspace
* being used as input (m_ws data member). Same applies to the logs.
*/
void LoadEventNexus::loadEvents(API::Progress *const prog,
                                const bool monitors) {
  bool metaDataOnly = getProperty("MetaDataOnly");

  // Get the time filters
  setTimeFilters(monitors);

  // The run_start will be loaded from the pulse times.
  DateAndTime run_start(0, 0);
  // Initialize the counter of bad TOFs
  bad_tofs = 0;
  int nPeriods = 1;
  auto periodLog = make_unique<const TimeSeriesProperty<int>>("period_log");
  if (!m_logs_loaded_correctly) {
    if (loadlogs) {
      prog->doReport("Loading DAS logs");

      m_allBanksPulseTimes = runLoadNexusLogs<EventWorkspaceCollection_sptr>(
          m_filename, m_ws, *this, true, nPeriods, periodLog);

      run_start = m_ws->getFirstPulseTime();
      m_logs_loaded_correctly = true;
    } else {
      g_log.information() << "Skipping the loading of sample logs!\n"
                          << "Reading the start time directly from /"
                          << m_top_entry_name << "/start_time\n";
      // start_time is read and set
      m_file->openPath("/");
      m_file->openGroup(m_top_entry_name, "NXentry");
      std::string tmp;
      m_file->readData("start_time", tmp);
      m_file->closeGroup();
      run_start = createFromSanitizedISO8601(tmp);
      m_ws->mutableRun().addProperty("run_start", run_start.toISO8601String(),
                                     true);
    }
  }
  m_ws->setNPeriods(
      nPeriods, periodLog); // This is how many workspaces we are going to make.

  // Make sure you have a non-NULL m_allBanksPulseTimes
  if (m_allBanksPulseTimes == nullptr) {
    std::vector<DateAndTime> temp;
    m_allBanksPulseTimes = boost::make_shared<BankPulseTimes>(temp);
  }

  if (!m_ws->getInstrument() || !m_instrument_loaded_correctly) {
    // Load the instrument (if not loaded before)
    prog->report("Loading instrument");
    m_instrument_loaded_correctly =
        loadInstrument(m_filename, m_ws, m_top_entry_name, this);

    if (!m_instrument_loaded_correctly)
      throw std::runtime_error(
          "Instrument was not initialized correctly! Loading cannot continue.");
  }

  // top level file information
  m_file->openPath("/");
  // Start with the base entry
  m_file->openGroup(m_top_entry_name, "NXentry");

  // Now we want to go through all the bankN_event entries
  vector<string> bankNames;
  vector<std::size_t> bankNumEvents;
  map<string, string> entries = m_file->getEntries();
  map<string, string>::const_iterator it = entries.begin();
  std::string classType = monitors ? "NXmonitor" : "NXevent_data";
  ::NeXus::Info info;
  bool oldNeXusFileNames(false);
  bool hasTotalCounts(true);
  bool haveWeights = false;
  for (; it != entries.end(); ++it) {
    std::string entry_name(it->first);
    std::string entry_class(it->second);
    if (entry_class == classType) {
      // open the group
      m_file->openGroup(entry_name, classType);

      // get the number of events
      std::size_t num = numEvents(*m_file, hasTotalCounts, oldNeXusFileNames);
      bankNames.push_back(entry_name);
      bankNumEvents.push_back(num);

      // Look for weights in simulated file
      try {
        m_file->openData("event_weight");
        haveWeights = true;
        m_file->closeData();
      } catch (::NeXus::Exception &) {
        // Swallow exception since flag is already false;
      }

      m_file->closeGroup();
    }
  }

  loadSampleDataISIScompatibility(*m_file, *m_ws);

  // Close the 'top entry' group (raw_data_1 for NexusProcessed, etc.)
  m_file->closeGroup();

  // Delete the output workspace name if it existed
  std::string outName = getPropertyValue("OutputWorkspace");
  if (AnalysisDataService::Instance().doesExist(outName))
    AnalysisDataService::Instance().remove(outName);

  // set more properties on the workspace
  try {
    // this is a static method that is why it is passing the
    // file object and the file path
    loadEntryMetadata<EventWorkspaceCollection_sptr>(m_filename, m_ws,
                                                     m_top_entry_name);
  } catch (std::runtime_error &e) {
    // Missing metadata is not a fatal error. Log and go on with your life
    g_log.error() << "Error loading metadata: " << e.what() << '\n';
  }

  // --------------------------- Time filtering
  // ------------------------------------
  double filter_time_start_sec, filter_time_stop_sec;
  filter_time_start_sec = getProperty("FilterByTimeStart");
  filter_time_stop_sec = getProperty("FilterByTimeStop");

  // Default to ALL pulse times
  bool is_time_filtered = false;
  filter_time_start = Types::Core::DateAndTime::minimum();
  filter_time_stop = Types::Core::DateAndTime::maximum();

  if (m_allBanksPulseTimes->numPulses > 0) {
    // If not specified, use the limits of doubles. Otherwise, convert from
    // seconds to absolute PulseTime
    if (filter_time_start_sec != EMPTY_DBL()) {
      filter_time_start = run_start + filter_time_start_sec;
      is_time_filtered = true;
    }

    if (filter_time_stop_sec != EMPTY_DBL()) {
      filter_time_stop = run_start + filter_time_stop_sec;
      is_time_filtered = true;
    }

    // Silly values?
    if (filter_time_stop < filter_time_start) {
      std::string msg = "Your ";
      if (monitors)
        msg += "monitor ";
      msg += "filter for time's Stop value is smaller than the Start value.";
      throw std::invalid_argument(msg);
    }
  }

  if (is_time_filtered) {
    // Now filter out the run, using the DateAndTime type.
    m_ws->mutableRun().filterByTime(filter_time_start, filter_time_stop);
  }

  if (metaDataOnly) {
    // Now, create a default X-vector for histogramming, with just 2 bins.
    auto axis = HistogramData::BinEdges{
        1, static_cast<double>(std::numeric_limits<uint32_t>::max()) * 0.1 - 1};
    // Set the binning axis using this.
    m_ws->setAllX(axis);

    createSpectraMapping(m_filename, monitors, std::vector<std::string>());
    return;
  }

  // --------- Loading only one bank ? ----------------------------------
  std::vector<std::string> someBanks = getProperty("BankName");
  bool SingleBankPixelsOnly = getProperty("SingleBankPixelsOnly");
  if ((!someBanks.empty()) && (!monitors)) {
    // check that all of the requested banks are in the file
    for (auto &someBank : someBanks) {
      bool foundIt = false;
      for (auto &bankName : bankNames) {
        if (bankName == someBank + "_events") {
          foundIt = true;
          break;
        }
      }
      if (!foundIt) {
        throw std::invalid_argument("No entry named '" + someBank +
                                    "' was found in the .NXS file.\n");
      }
    }

    // change the number of banks to load
    bankNames.clear();
    for (auto &someBank : someBanks)
      bankNames.push_back(someBank + "_events");

    // how many events are in a bank
    bankNumEvents.clear();
    bankNumEvents.assign(someBanks.size(),
                         1); // TODO this equally weights the banks

    if (!SingleBankPixelsOnly)
      someBanks.clear(); // Marker to load all pixels
  } else {
    someBanks.clear();
  }

  prog->report("Initializing all pixels");

  // Remove unused banks if parameter is set
  if (m_ws->getInstrument()->hasParameter("remove-unused-banks")) {
    std::vector<double> instrumentUnused =
        m_ws->getInstrument()->getNumberParameter("remove-unused-banks", true);
    if (!instrumentUnused.empty()) {
      const int unused = static_cast<int>(instrumentUnused.front());
      if (unused == 1)
        deleteBanks(m_ws, bankNames);
    }
  }
  //----------------- Pad Empty Pixels -------------------------------
  createSpectraMapping(m_filename, monitors, someBanks);

  // Set all (empty) event lists as sorted by pulse time. That way, calling
  // SortEvents will not try to sort these empty lists.
  for (size_t i = 0; i < m_ws->getNumberHistograms(); i++)
    m_ws->getSpectrum(i).setSortOrder(DataObjects::PULSETIME_SORT);

  // Count the limits to time of flight
  shortest_tof =
      static_cast<double>(std::numeric_limits<uint32_t>::max()) * 0.1;
  longest_tof = 0.;

  bool loaded{false};
  if (canUseParallelLoader(haveWeights, oldNeXusFileNames, classType)) {
    auto ws = m_ws->getSingleHeldWorkspace();
    m_file->close();
    try {
      ParallelEventLoader::load(*ws, m_filename, m_top_entry_name, bankNames,
                                event_id_is_spec);
      g_log.information() << "Used ParallelEventLoader.\n";
      loaded = true;
      shortest_tof = 0.0;
      longest_tof = 1e10;
    } catch (const std::runtime_error &) {
      g_log.warning()
          << "ParallelEventLoader failed, falling back to default loader.\n";
    }
    safeOpenFile(m_filename);
  }
  if (!loaded) {
    bool precount = getProperty("Precount");
    int chunk = getProperty("ChunkNumber");
    int totalChunks = getProperty("TotalChunks");
    DefaultEventLoader::load(this, *m_ws, haveWeights, event_id_is_spec,
                             bankNames, periodLog->valuesAsVector(), classType,
                             bankNumEvents, oldNeXusFileNames, precount, chunk,
                             totalChunks);
  }

  // Info reporting
  const std::size_t eventsLoaded = m_ws->getNumberEvents();
  g_log.information() << "Read " << eventsLoaded << " events"
                      << ". Shortest TOF: " << shortest_tof
                      << " microsec; longest TOF: " << longest_tof
                      << " microsec.\n";

  if (shortest_tof < 0)
    g_log.warning() << "The shortest TOF was negative! At least 1 event has an "
                       "invalid time-of-flight.\n";
  if (bad_tofs > 0)
    g_log.warning() << "Found " << bad_tofs << " events with TOF > 2e8. This "
                                               "may indicate errors in the raw "
                                               "TOF data.\n";

  // Use T0 offset from TOPAZ Parameter file if it exists
  if (m_ws->getInstrument()->hasParameter("T0")) {
    std::vector<double> instrumentT0 =
        m_ws->getInstrument()->getNumberParameter("T0", true);
    if (!instrumentT0.empty()) {
      const double mT0 = instrumentT0.front();
      if (mT0 != 0.0) {
        int64_t numHistograms =
            static_cast<int64_t>(m_ws->getNumberHistograms());
        PARALLEL_FOR_IF(Kernel::threadSafe(*m_ws))
        for (int64_t i = 0; i < numHistograms; ++i) {
          PARALLEL_START_INTERUPT_REGION
          // Do the offsetting
          m_ws->getSpectrum(i).addTof(mT0);
          PARALLEL_END_INTERUPT_REGION
        }
        PARALLEL_CHECK_INTERUPT_REGION
        // set T0 in the run parameters
        API::Run &run = m_ws->mutableRun();
        run.addProperty<double>("T0", mT0, true);
      }
    }
  }
  // Now, create a default X-vector for histogramming, with just 2 bins.
  if (eventsLoaded > 0)
    m_ws->setAllX(HistogramData::BinEdges{shortest_tof - 1, longest_tof + 1});
  else
    m_ws->setAllX(HistogramData::BinEdges{0.0, 1.0});

  // if there is time_of_flight load it
  adjustTimeOfFlightISISLegacy(*m_file, m_ws, m_top_entry_name, classType);
}

//-----------------------------------------------------------------------------
/** Load the instrument from the nexus file
*
*  @param nexusfilename :: The name of the nexus file being loaded
*  @param localWorkspace :: EventWorkspaceCollection in which to put the
*instrument
*geometry
*  @param top_entry_name :: entry name at the top of the Nexus file
*  @param alg :: Handle of the algorithm
*  @return true if successful
*/
template <>
bool LoadEventNexus::runLoadIDFFromNexus<EventWorkspaceCollection_sptr>(
    const std::string &nexusfilename,
    EventWorkspaceCollection_sptr localWorkspace,
    const std::string &top_entry_name, Algorithm *alg) {
  auto ws = localWorkspace->getSingleHeldWorkspace();
  auto hasLoaded = runLoadIDFFromNexus<MatrixWorkspace_sptr>(
      nexusfilename, ws, top_entry_name, alg);
  localWorkspace->setInstrument(ws->getInstrument());
  return hasLoaded;
}

/** method used to return instrument name for some old ISIS files where it is
* not written properly within the instrument
* @param hFile :: A reference to the NeXus file opened at the root entry
*/
std::string
LoadEventNexus::readInstrumentFromISIS_VMSCompat(::NeXus::File &hFile) {
  std::string instrumentName;
  try {
    hFile.openGroup("isis_vms_compat", "IXvms");
  } catch (std::runtime_error &) {
    return instrumentName;
  }
  try {
    hFile.openData("NAME");
  } catch (std::runtime_error &) {
    hFile.closeGroup();
    return instrumentName;
  }

  instrumentName = hFile.getStrData();
  hFile.closeData();
  hFile.closeGroup();

  return instrumentName;
}

//-----------------------------------------------------------------------------
/** Load the instrument definition file specified by info in the NXS file for
* a EventWorkspaceCollection
*
*  @param nexusfilename :: Used to pick the instrument.
*  @param localWorkspace :: EventWorkspaceCollection in which to put the
*instrument
*geometry
*  @param top_entry_name :: entry name at the top of the NXS file
*  @param alg :: Handle of the algorithm
*  @return true if successful
*/
template <>
bool LoadEventNexus::runLoadInstrument<EventWorkspaceCollection_sptr>(
    const std::string &nexusfilename,
    EventWorkspaceCollection_sptr localWorkspace,
    const std::string &top_entry_name, Algorithm *alg) {
  auto ws = localWorkspace->getSingleHeldWorkspace();
  auto hasLoaded = runLoadInstrument<MatrixWorkspace_sptr>(nexusfilename, ws,
                                                           top_entry_name, alg);
  localWorkspace->setInstrument(ws->getInstrument());
  return hasLoaded;
}

//-----------------------------------------------------------------------------
/**
* Deletes banks for a workspace given the bank names.
* @param workspace :: The workspace to contain the spectra mapping
* @param bankNames :: Bank names that are in Nexus file
*/
void LoadEventNexus::deleteBanks(EventWorkspaceCollection_sptr workspace,
                                 std::vector<std::string> bankNames) {
  Instrument_sptr inst = boost::const_pointer_cast<Instrument>(
      workspace->getInstrument()->baseInstrument());
  // Build a list of Rectangular Detectors
  std::vector<boost::shared_ptr<RectangularDetector>> detList;
  for (int i = 0; i < inst->nelements(); i++) {
    boost::shared_ptr<RectangularDetector> det;
    boost::shared_ptr<ICompAssembly> assem;
    boost::shared_ptr<ICompAssembly> assem2;

    det = boost::dynamic_pointer_cast<RectangularDetector>((*inst)[i]);
    if (det) {
      detList.push_back(det);
    } else {
      // Also, look in the first sub-level for RectangularDetectors (e.g. PG3).
      // We are not doing a full recursive search since that will be very long
      // for lots of pixels.
      assem = boost::dynamic_pointer_cast<ICompAssembly>((*inst)[i]);
      if (assem) {
        for (int j = 0; j < assem->nelements(); j++) {
          det = boost::dynamic_pointer_cast<RectangularDetector>((*assem)[j]);
          if (det) {
            detList.push_back(det);

          } else {
            // Also, look in the second sub-level for RectangularDetectors (e.g.
            // PG3).
            // We are not doing a full recursive search since that will be very
            // long for lots of pixels.
            assem2 = boost::dynamic_pointer_cast<ICompAssembly>((*assem)[j]);
            if (assem2) {
              for (int k = 0; k < assem2->nelements(); k++) {
                det = boost::dynamic_pointer_cast<RectangularDetector>(
                    (*assem2)[k]);
                if (det) {
                  detList.push_back(det);
                }
              }
            }
          }
        }
      }
    }
  }
  if (detList.empty())
    return;
  for (auto &det : detList) {
    bool keep = false;
    std::string det_name = det->getName();
    for (auto &bankName : bankNames) {
      size_t pos = bankName.find("_events");
      if (det_name == bankName.substr(0, pos))
        keep = true;
      if (keep)
        break;
    }
    if (!keep) {
      boost::shared_ptr<const IComponent> parent =
          inst->getComponentByName(det_name);
      std::vector<Geometry::IComponent_const_sptr> children;
      boost::shared_ptr<const Geometry::ICompAssembly> asmb =
          boost::dynamic_pointer_cast<const Geometry::ICompAssembly>(parent);
      asmb->getChildren(children, false);
      for (auto &col : children) {
        boost::shared_ptr<const Geometry::ICompAssembly> asmb2 =
            boost::dynamic_pointer_cast<const Geometry::ICompAssembly>(col);
        std::vector<Geometry::IComponent_const_sptr> grandchildren;
        asmb2->getChildren(grandchildren, false);

        for (auto &row : grandchildren) {
          Detector *d =
              dynamic_cast<Detector *>(const_cast<IComponent *>(row.get()));
          if (d)
            inst->removeDetector(d);
        }
      }
      IComponent *comp = dynamic_cast<IComponent *>(det.get());
      inst->remove(comp);
    }
  }
}
//-----------------------------------------------------------------------------
/**
* Create the required spectra mapping. If the file contains an isis_vms_compat
* block then
* the mapping is read from there, otherwise a 1:1 map with the instrument is
* created (along
* with the associated spectra axis)
* @param nxsfile :: The name of a nexus file to load the mapping from
* @param monitorsOnly :: Load only the monitors is true
* @param bankNames :: An optional bank name for loading specified banks
*/
void LoadEventNexus::createSpectraMapping(
    const std::string &nxsfile, const bool monitorsOnly,
    const std::vector<std::string> &bankNames) {
  LoadEventNexusIndexSetup indexSetup(
      m_ws->getSingleHeldWorkspace(), getProperty("SpectrumMin"),
      getProperty("SpectrumMax"), getProperty("SpectrumList"), communicator());
  if (!monitorsOnly && !bankNames.empty()) {
    if (!isDefault("SpectrumMin") || !isDefault("SpectrumMax") ||
        !isDefault("SpectrumList"))
      g_log.warning() << "Spectrum min/max/list selection ignored when "
                         "`SingleBankPixelsOnly` is enabled\n";
    m_ws->setIndexInfo(indexSetup.makeIndexInfo(bankNames));
    g_log.debug() << "Populated spectra map for select banks\n";
  } else if (auto mapping = loadISISVMSSpectraMapping(m_top_entry_name)) {
    if (monitorsOnly) {
      g_log.debug() << "Loading only monitor spectra from " << nxsfile << "\n";
    } else {
      g_log.debug() << "Loading only detector spectra from " << nxsfile << "\n";
    }
    m_ws->setIndexInfo(indexSetup.makeIndexInfo(*mapping, monitorsOnly));
  } else {
    g_log.debug() << "No custom spectra mapping found, continuing with default "
                     "1:1 mapping of spectrum:detectorID\n";
    m_ws->setIndexInfo(indexSetup.makeIndexInfo());
    g_log.debug() << "Populated 1:1 spectra map for the whole instrument \n";
  }
  std::tie(m_specMin, m_specMax) = indexSetup.eventIDLimits();
}

//-----------------------------------------------------------------------------
/**
* Returns whether the file contains monitors with events in them
* @returns True if the file contains monitors with event data, false otherwise
*/
bool LoadEventNexus::hasEventMonitors() {
  bool result(false);
  // Determine whether to load histograms or events
  try {
    m_file->openPath("/" + m_top_entry_name);
    // Start with the base entry
    using string_map_t = std::map<std::string, std::string>;
    // Now we want to go through and find the monitors
    string_map_t entries = m_file->getEntries();
    for (string_map_t::const_iterator it = entries.begin(); it != entries.end();
         ++it) {
      if (it->second == "NXmonitor") {
        m_file->openGroup(it->first, it->second);
        break;
      }
    }
    bool hasTotalCounts = false;
    bool oldNeXusFileNames = false;
    result = numEvents(*m_file, hasTotalCounts, oldNeXusFileNames) > 0;
    m_file->closeGroup();
  } catch (::NeXus::Exception &) {
    result = false;
  }
  return result;
}

//-----------------------------------------------------------------------------
/**
* Load the Monitors from the NeXus file into a workspace. The original
* workspace name is used and appended with _monitors.
*
*/
void LoadEventNexus::runLoadMonitors() {
  std::string mon_wsname = this->getProperty("OutputWorkspace");
  mon_wsname.append("_monitors");

  IAlgorithm_sptr loadMonitors =
      this->createChildAlgorithm("LoadNexusMonitors");
  g_log.information("Loading monitors from NeXus file...");
  loadMonitors->setPropertyValue("Filename", m_filename);
  g_log.information() << "New workspace name for monitors: " << mon_wsname
                      << '\n';
  loadMonitors->setPropertyValue("OutputWorkspace", mon_wsname);
  loadMonitors->setPropertyValue("LoadOnly",
                                 this->getProperty("MonitorsLoadOnly"));
  loadMonitors->setPropertyValue("NXentryName",
                                 this->getProperty("NXentryName"));
  loadMonitors->execute();
  Workspace_sptr monsOut = loadMonitors->getProperty("OutputWorkspace");
  // create the output workspace property on the fly
  this->declareProperty(Kernel::make_unique<WorkspaceProperty<Workspace>>(
                            "MonitorWorkspace", mon_wsname, Direction::Output),
                        "Monitors from the Event NeXus file");
  this->setProperty("MonitorWorkspace", monsOut);

  // The output will either be a group workspace or a matrix workspace
  MatrixWorkspace_sptr mons =
      boost::dynamic_pointer_cast<MatrixWorkspace>(monsOut);
  if (mons) {
    // Set the internal monitor workspace pointer as well
    m_ws->setMonitorWorkspace(mons);

    filterDuringPause(mons);
  } else {
    WorkspaceGroup_sptr monsGrp =
        boost::dynamic_pointer_cast<WorkspaceGroup>(monsOut);
    if (monsGrp) {
      // declare a property for each member of the group
      for (int i = 0; i < monsGrp->getNumberOfEntries(); i++) {
        std::stringstream ssWsName;
        ssWsName << mon_wsname << "_" << i + 1;
        std::stringstream ssPropName;
        ssPropName << "MonitorWorkspace"
                   << "_" << i + 1;
        this->declareProperty(
            Kernel::make_unique<WorkspaceProperty<MatrixWorkspace>>(
                ssPropName.str(), ssWsName.str(), Direction::Output),
            "Monitors from the Event NeXus file");
        this->setProperty(ssPropName.str(), monsGrp->getItem(i));
      }
    }
  }
}

//
/**
* Load a spectra mapping from the given file. This currently checks for the
* existence of
* an isis_vms_compat block in the file, if it exists it pulls out the spectra
* mapping listed there
* @param entry_name :: name of the NXentry to open.
* @returns True if the mapping was loaded or false if the block does not exist
*/
std::unique_ptr<std::pair<std::vector<int32_t>, std::vector<int32_t>>>
LoadEventNexus::loadISISVMSSpectraMapping(const std::string &entry_name) {
  const std::string vms_str = "/isis_vms_compat";
  try {
    g_log.debug() << "Attempting to load custom spectra mapping from '"
                  << entry_name << vms_str << "'.\n";
    m_file->openPath("/" + entry_name + vms_str);
  } catch (::NeXus::Exception &) {
    return nullptr; // Doesn't exist
  }

  // The ISIS spectrum mapping is defined by 2 arrays in isis_vms_compat block:
  //   UDET - An array of detector IDs
  //   SPEC - An array of spectrum numbers
  // There sizes must match. Hardware allows more than one detector ID to be
  // mapped to a single spectrum
  // and this is encoded in the SPEC/UDET arrays by repeating the spectrum
  // number in the array
  // for each mapped detector, e.g.
  //
  // 1 1001
  // 1 1002
  // 2 2001
  // 3 3001
  //
  // defines 3 spectra, where the first spectrum contains 2 detectors

  // UDET
  m_file->openData("UDET");
  std::vector<int32_t> udet;
  m_file->getData(udet);
  m_file->closeData();
  // SPEC
  m_file->openData("SPEC");
  std::vector<int32_t> spec;
  m_file->getData(spec);
  m_file->closeData();
  // Go up/back. this assumes one level for entry name and a second level
  // for /isis_vms_compat, typically: /raw_data_1/isis_vms_compat
  m_file->closeGroup();
  m_file->closeGroup();

  // The spec array will contain a spectrum number for each udet but the
  // spectrum number
  // may be the same for more that one detector
  const size_t ndets(udet.size());
  if (ndets != spec.size()) {
    std::ostringstream os;
    os << "UDET/SPEC list size mismatch. UDET=" << udet.size()
       << ", SPEC=" << spec.size() << "\n";
    throw std::runtime_error(os.str());
  }
  // If mapping loaded the event ID is the spectrum number and not det ID
  this->event_id_is_spec = true;
  return Kernel::make_unique<
      std::pair<std::vector<int32_t>, std::vector<int32_t>>>(std::move(spec),
                                                             std::move(udet));
}

/**
* Set the filters on TOF.
* @param monitors :: If true check the monitor properties else use the standard
* ones
*/
void LoadEventNexus::setTimeFilters(const bool monitors) {
  // Get the limits to the filter
  std::string prefix("Filter");
  if (monitors)
    prefix += "Mon";

  filter_tof_min = getProperty(prefix + "ByTofMin");
  filter_tof_max = getProperty(prefix + "ByTofMax");
  if ((filter_tof_min == EMPTY_DBL()) && (filter_tof_max == EMPTY_DBL())) {
    // Nothing specified. Include everything
    filter_tof_min = -1e20;
    filter_tof_max = +1e20;
  } else if ((filter_tof_min != EMPTY_DBL()) &&
             (filter_tof_max != EMPTY_DBL())) {
    // Both specified. Keep these values
  } else {
    std::string msg("You must specify both min & max or neither TOF filters");
    if (monitors)
      msg = " for the monitors.";
    throw std::invalid_argument(msg);
  }
}

//-----------------------------------------------------------------------------

/**
* Load information of the sample. It is valid only for ISIS it get the
* information from the group isis_vms_compat.
*
* If it does not find this group, it assumes that there is nothing to do.
* But, if the information is there, but not in the way it was expected, it
* will log the occurrence.
*
* @note: It does essentially the same thing of the
* method: LoadISISNexus2::loadSampleData
*
* @param file : handle to the nexus file
* @param WS : pointer to the workspace
*/
void LoadEventNexus::loadSampleDataISIScompatibility(
    ::NeXus::File &file, EventWorkspaceCollection &WS) {
  try {
    file.openGroup("isis_vms_compat", "IXvms");
  } catch (::NeXus::Exception &) {
    // No problem, it just means that this entry does not exist
    return;
  }

  // read the data
  try {
    std::vector<int32_t> spb;
    std::vector<float> rspb;
    file.readData("SPB", spb);
    file.readData("RSPB", rspb);

    WS.setGeometryFlag(spb[2]); // the flag is in the third value
    WS.setThickness(rspb[3]);
    WS.setHeight(rspb[4]);
    WS.setWidth(rspb[5]);
  } catch (::NeXus::Exception &ex) {
    // it means that the data was not as expected, report the problem
    std::stringstream s;
    s << "Wrong definition found in isis_vms_compat :> " << ex.what();
    file.closeGroup();
    throw std::runtime_error(s.str());
  }

  file.closeGroup();
}

/**
 * Makes sure that m_file is a valid and open NeXus::File object.
 * Throws if there is an exception opening the file.
 *
 * @param fname name of the nexus file to open
 */
void LoadEventNexus::safeOpenFile(const std::string fname) {
  try {
    m_file = Kernel::make_unique<::NeXus::File>(m_filename, NXACC_READ);
  } catch (std::runtime_error &e) {
    throw std::runtime_error("Severe failure when trying to open NeXus file: " +
                             std::string(e.what()));
  }
  // make sure that by no means we could dereference NULL later on
  if (!m_file) {
    throw std::runtime_error("An unexpected failure happened, unable to "
                             "initialize file object when trying to open NeXus "
                             "file: " +
                             fname);
  }
}

/// The parallel loader currently has no support for a series of special cases,
/// as indicated by the return value of this method.
bool LoadEventNexus::canUseParallelLoader(const bool haveWeights,
                                          const bool oldNeXusFileNames,
                                          const std::string &classType) const {
#ifndef MPI_EXPERIMENTAL
  // Actually the parallel loader would work also in non-MPI builds but it is
  // likely to be slower than the default loader and may also exhibit unusual
  // behavior for non-standard Nexus files.
  return false;
#else
  bool useParallelLoader = getProperty("UseParallelLoader");
  if (!useParallelLoader)
    return false;
#endif
  if (m_ws->nPeriods() != 1)
    return false;
  if (haveWeights)
    return false;
  if (oldNeXusFileNames)
    return false;
  if (filter_tof_min != -1e20 || filter_tof_max != 1e20)
    return false;
  if (filter_time_start != Types::Core::DateAndTime::minimum() ||
      filter_time_stop != Types::Core::DateAndTime::maximum())
    return false;
  if (!isDefault("CompressTolerance") || !isDefault("SpectrumMin") ||
      !isDefault("SpectrumMax") || !isDefault("SpectrumList") ||
      !isDefault("ChunkNumber"))
    return false;
  if (classType != "NXevent_data")
    return false;
  return true;
}

Parallel::ExecutionMode LoadEventNexus::getParallelExecutionMode(
    const std::map<std::string, Parallel::StorageMode> &storageModes) const {
  static_cast<void>(storageModes);
  return Parallel::ExecutionMode::Distributed;
}

} // namespace DataHandling
} // namespace Mantid