ParallelRunner.cpp

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// 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 "MantidFrameworkTestHelpers/ParallelRunner.h"
#include "MantidParallel/ThreadingBackend.h"
 
#include <algorithm>
 
using namespace Mantid::Parallel;
 
namespace ParallelTestHelpers {
 
ParallelRunner::ParallelRunner() {
  Communicator comm;
  // Fake parallelism via threads if there is only 1 MPI rank
  if (comm.size() == 1) {
    // 3 is an arbitrary choice. We need more than 1 since that would be a
    // trivial case, 2 seems like a special case that might make some bugs
    // invisible.
    int threads = std::max(3, static_cast<int>(std::thread::hardware_concurrency()));
    m_backend = std::make_shared<detail::ThreadingBackend>(threads);
  }
  m_serialBackend = std::make_shared<detail::ThreadingBackend>(1);
}
 
ParallelRunner::ParallelRunner(const int threads) {
  Communicator comm;
  // Fake parallelism via threads if there is only 1 MPI rank, but fail if there
  // are MPI ranks that do not match the number of requested threads.
  if (comm.size() != 1 && comm.size() != threads)
    throw("ParallelRunner: number of requested threads does not match number "
          "of MPI ranks");
  if (comm.size() == 1)
    m_backend = std::make_shared<detail::ThreadingBackend>(threads);
  m_serialBackend = std::make_shared<detail::ThreadingBackend>(1);
}
 
int ParallelRunner::size() const {
  if (m_backend)
    return m_backend->size();
  Communicator comm;
  return comm.size();
}
 
} // namespace ParallelTestHelpers