parallel_hilbert.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2025 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner

// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.

// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA


#ifndef LIBMESH_PARALLEL_HILBERT_H
#define LIBMESH_PARALLEL_HILBERT_H

// This class contains all the functionality for bin sorting
// Templated on the type of keys you will be sorting and the
// type of iterator you will be using.

#include "libmesh/libmesh_config.h"

#if defined(LIBMESH_HAVE_LIBHILBERT)

// TIMPI includes
#include "timpi/standard_type.h"

// C/C++ includes

// So many implicit-fallthrough warnings in crazy libHilbert macros...
#include "libmesh/ignore_warnings.h"
#include "hilbert.h"
#include "libmesh/restore_warnings.h"

#include <cstddef>

namespace TIMPI {

#ifdef LIBMESH_HAVE_MPI
// A StandardType<> specialization to return a derived MPI datatype
// to handle communication of HilbertIndices.  We use a singleton
// pattern here because a global variable would have tried to call
// MPI functions before MPI got initialized.
template <>
class StandardType<Hilbert::HilbertIndices> : public DataType
{
public:
  explicit
  StandardType(const Hilbert::HilbertIndices * =nullptr)
  {
    _datatype = DataType(StandardType<Hilbert::inttype>(), 3);
  }

  StandardType(const StandardType<Hilbert::HilbertIndices> & t)
    : DataType()
  {
    timpi_call_mpi (MPI_Type_dup (t._datatype, &_datatype));
  }

  ~StandardType() { this->free(); }

  static const bool is_fixed_type = true;
};

#endif // LIBMESH_HAVE_MPI

} // namespace TIMPI


namespace libMesh {

namespace Parallel {

#ifdef LIBMESH_ENABLE_UNIQUE_ID
typedef std::pair<Hilbert::HilbertIndices, unique_id_type> DofObjectKey;
#else
typedef Hilbert::HilbertIndices DofObjectKey;
#endif

} // namespace Parallel

} // namespace libMesh


namespace Hilbert {

// This has to be in the Hilbert namespace for Koenig lookup to work?
// g++ doesn't find it if it's in the global namespace.
// XCode didn't find it in the libMesh namespace.
#ifdef LIBMESH_ENABLE_UNIQUE_ID
inline
std::ostream & operator << (std::ostream & os,
                            const libMesh::Parallel::DofObjectKey & hilbert_pair)
{
  os << '(' << hilbert_pair.first << ',' << hilbert_pair.second << ')' << std::endl;
  return os;
}
#endif

}


// Appropriate operator< definitions for std::pair let the same code handle
// both DofObjectKey types

inline
void dofobjectkey_max_op (libMesh::Parallel::DofObjectKey * in,
                          libMesh::Parallel::DofObjectKey * inout,
                          int * len, void *)
{
  // When (*in <= *inout), then inout already contains max(*in,*inout)
  // Otherwise we need to copy from in.
  for (int i=0; i<*len; i++, in++, inout++)
    if (*inout < *in)
      *inout = *in;
}

inline
void dofobjectkey_min_op (libMesh::Parallel::DofObjectKey * in,
                          libMesh::Parallel::DofObjectKey * inout,
                          int * len, void *)
{
  // When (*in >= *inout), then inout already contains min(*in,*inout)
  // Otherwise we need to copy from in.
  for (int i=0; i<*len; i++, in++, inout++)
    if (*in < *inout)
      *inout = *in;
}

#endif // LIBMESH_HAVE_LIBHILBERT

#endif // LIBMESH_PARALLEL_HILBERT_H