mpihelper.hh

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// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
// SPDX-FileCopyrightInfo: Copyright © DUNE Project contributors, see file LICENSE.md in module root
// SPDX-License-Identifier: LicenseRef-GPL-2.0-only-with-DUNE-exception
#ifndef DUNE_COMMON_PARALLEL_MPIHELPER_HH
#define DUNE_COMMON_PARALLEL_MPIHELPER_HH

#include <cassert>
#include <mutex>

#if HAVE_MPI
#include <mpi.h>
#endif

#include <dune/common/exceptions.hh>
#include <dune/common/visibility.hh>
#include <dune/common/parallel/communication.hh>
#include <dune/common/parallel/mpicommunication.hh>

#if HAVE_MPI
#include <dune/common/stdstreams.hh>
#endif

namespace Dune
{
  class FakeMPIHelper
  {
  public:
    constexpr static bool isFake = true;

    typedef No_Comm MPICommunicator;

    DUNE_EXPORT static MPICommunicator getCommunicator ()
    {
      static MPICommunicator comm;
      return comm;
    }

    static MPICommunicator getLocalCommunicator ()
    {
      return getCommunicator();
    }


    static Communication<MPICommunicator>
    getCommunication()
    {
      return Communication<MPICommunicator>(getCommunicator());
    }

    DUNE_EXPORT static FakeMPIHelper& instance([[maybe_unused]] int argc,
                                               [[maybe_unused]] char** argv)
    {
      return instance();
    }

    DUNE_EXPORT static FakeMPIHelper& instance()
    {
      static FakeMPIHelper singleton;
      return singleton;
    }

    int rank () const { return 0; }
    int size () const { return 1; }

  private:
    FakeMPIHelper() {}
    FakeMPIHelper(const FakeMPIHelper&);
    FakeMPIHelper& operator=(const FakeMPIHelper);
  };

#if HAVE_MPI

  class MPIHelper
  {
  public:
    constexpr static bool isFake = false;

    typedef MPI_Comm MPICommunicator;

    static MPICommunicator getCommunicator ()
    {
      return MPI_COMM_WORLD;
    }

    static MPICommunicator getLocalCommunicator ()
    {
      return MPI_COMM_SELF;
    }

    static Communication<MPICommunicator>
    getCommunication()
    {
      return Communication<MPICommunicator>(getCommunicator());
    }
    DUNE_EXPORT static MPIHelper& instance(int& argc, char**& argv)
    {
      return instance(&argc, &argv);
    }

    DUNE_EXPORT static MPIHelper& instance(int* argc = nullptr, char*** argv = nullptr)
    {
      assert((argc == nullptr) == (argv == nullptr));
      static MPIHelper instance{argc, argv};
      return instance;
    }

    int rank () const { return rank_; }
    int size () const { return size_; }

    ~MPIHelper()
    {
      int wasFinalized = -1;
      MPI_Finalized( &wasFinalized );
      if(!wasFinalized && initializedHere_)
      {
        MPI_Finalize();
        dverb << "Called MPI_Finalize on p=" << rank_ << "!" <<std::endl;
      }

    }

  private:
    int rank_;
    int size_;
    bool initializedHere_;
    void prevent_warning(int){}

    MPIHelper(int* argc, char*** argv)
    : initializedHere_(false)
    {
      int wasInitialized = -1;
      MPI_Initialized( &wasInitialized );
      if(!wasInitialized)
      {
        rank_ = -1;
        size_ = -1;
        static int is_initialized = MPI_Init(argc, argv);
        prevent_warning(is_initialized);
        initializedHere_ = true;
      }

      MPI_Comm_rank(MPI_COMM_WORLD,&rank_);
      MPI_Comm_size(MPI_COMM_WORLD,&size_);

      assert( rank_ >= 0 );
      assert( size_ >= 1 );

      dverb << "Called  MPI_Init on p=" << rank_ << "!" << std::endl;
    }

    MPIHelper(const MPIHelper&);
    MPIHelper& operator=(const MPIHelper);
  };
#else // !HAVE_MPI
  // We do not have MPI therefore FakeMPIHelper
  // is the MPIHelper
  typedef FakeMPIHelper MPIHelper;

#endif // !HAVE_MPI

} // end namespace Dune

#endif // DUNE_COMMON_PARALLEL_MPIHELPER_HH