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#ifndef TEMPLAT_PARALLEL_MPI_CARTESIAN_MPICARTESIANNEIGHBOURSSINGLEDIMENSION_H
#define TEMPLAT_PARALLEL_MPI_CARTESIAN_MPICARTESIANNEIGHBOURSSINGLEDIMENSION_H

/* This file is part of TempLat, available at https://cosmolattice.github.io/templat .
   Copyright 2021-2026 The TempLat authors, see AUTHORS.md.
   Released under the MIT license, see LICENSE.md. */

// File info: Main contributor(s): Wessel Valkenburg, Year: 2019

#include "TempLat/parallel/mpi/cartesian/mpicartesiangroup.h"

namespace TempLat
{

  class MPICartesianNeighboursSingleDimension
  {
  public:
    // Put public methods here. These should change very little over time.
    MPICartesianNeighboursSingleDimension(MPICartesianGroup cartesianGroup, ptrdiff_t dimension)
        : mCartesianGroup(cartesianGroup), mDimension(dimension), mUpperNeighbourRank(0), mLowerNeighbourRank(0)
    {
#ifdef HAVE_MPI
      const int displacement = 1;
      MPI_Cart_shift(mCartesianGroup.getComm(), mDimension, displacement, &mLowerNeighbourRank, &mUpperNeighbourRank);
#endif
    }

    const int &getUpper() const { return mUpperNeighbourRank; }

    const int &getLower() const { return mLowerNeighbourRank; }

    friend std::ostream &operator<<(std::ostream &ostream, const MPICartesianNeighboursSingleDimension &nsd)
    {
      ostream << "Dimension: " << nsd.mDimension << " - lower neighbour: " << nsd.mLowerNeighbourRank
              << " - upper neighbour: " << nsd.mUpperNeighbourRank;
      return ostream;
    }

  private:
    /* Put all member variables and private methods here. These may change arbitrarily. */
    MPICartesianGroup mCartesianGroup;
    ptrdiff_t mDimension;
    int mUpperNeighbourRank;
    int mLowerNeighbourRank;
  };
} // namespace TempLat

#endif