parallelalgorithm.hh

Go to the documentation of this file.

// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
 
// SPDX-FileCopyrightText: Copyright © DUNE-FUFEM Project contributors, see file AUTHORS.md
// SPDX-License-Identifier: LicenseRef-GPL-2.0-only-with-DUNE-exception OR LGPL-3.0-or-later
 
#ifndef DUNE_FUFEM_PARALLEL_PARALLELALGORITHM_HH
#define DUNE_FUFEM_PARALLEL_PARALLELALGORITHM_HH
 
#include <cstddef>
#include <vector>
#include <thread>
 
#include <dune/common/iteratorrange.hh>
 
#include <dune/fufem/parallel/barrier.hh>
 
 
 
namespace Dune {
namespace Fufem {
 
 
template<class Range>
static auto rangeSegment(Range& range, std::size_t i, std::size_t n) {
  std::size_t length = range.size() / n;
  std::size_t remainder = range.size() % n;
  auto begin = length*i + std::min(remainder, i);
  auto end = length*(i+1) + std::min(remainder, i+1);
  return Dune::IteratorRange(range.begin()+begin, range.begin()+end);
}
 
 
 
 
namespace Impl {
 
class ParallelAlgorithmThreadHelper
{
public:
  ParallelAlgorithmThreadHelper(std::size_t threadCount, std::size_t threadIndex, Dune::Fufem::Barrier& barrier):
    threadCount_(threadCount),
    threadIndex_(threadIndex),
    barrier_(barrier)
  {}
 
  template<class Range, class CallBack>
  void forEach(Range&& range, CallBack&& callBack) const
  {
    for (auto&& entry : rangeSegment(range, threadIndex_, threadCount_))
      callBack(entry);
    barrier_.arrive_and_wait();
  }
 
  template<class ColorPartition, class CallBack>
  void coloredForEach(const ColorPartition& partition, CallBack&& callBack) const
  {
    for (auto&& singleColorRange : partition)
      forEach(singleColorRange, callBack);
  }
 
  std::size_t threadIndex() const
  {
    return threadIndex_;
  }
 
  std::size_t threadCount() const
  {
    return threadCount_;
  }
 
  Dune::Fufem::Barrier& barrier() const
  {
    return barrier_;;
  }
 
private:
  std::size_t threadCount_;
  std::size_t threadIndex_;
  Dune::Fufem::Barrier& barrier_;
};
 
} // namespace Impl
 
 
 
template<class F>
void parallelAlgorithm(std::size_t threadCount, F&& threadImp)
{
  Dune::Fufem::Barrier barrier(threadCount);
 
  std::vector<std::thread> threads;
  for (std::size_t i=0; i<threadCount; ++i)
    threads.emplace_back(threadImp, Impl::ParallelAlgorithmThreadHelper(threadCount, i, barrier));
  for (auto& thread : threads)
    thread.join();
}
 
 
 
} // namespace Fufem
} // namespace Dune
 
 
#endif // DUNE_FUFEM_PARALLEL_PARALLELALGORITHM_HH