mpi_stub.h

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// -----------------------------------------------------------------------------
//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception OR LGPL-2.1-or-later
// Copyright (C) 2022 - 2026 by the deal.II authors
//
// This file is part of the deal.II library.
//
// Detailed license information governing the source code and contributions
// can be found in LICENSE.md and CONTRIBUTING.md at the top level directory.
//
// -----------------------------------------------------------------------------
 
#ifndef dealii_mpi_stub_h
#define dealii_mpi_stub_h
 
#include <deal.II/base/config.h>
 
// If we have mpi.h then include it. Otherwise, define some common MPI data
// types and global constants for the no-MPI case. This way we can still use,
// e.g., MPI_Comm in the API.
 
#if defined(DEAL_II_WITH_MPI)
 
DEAL_II_DISABLE_EXTRA_DIAGNOSTICS
// Avoid a macro collision between mpc.h and MPICH's C++ headers by
// undefining DOUBLE_COMPLEX and LONG_DOUBLE_COMPLEX before including <mpi.h>
// On some macOS setups mpc.h (from libmpc) defines macros
// DOUBLE_COMPLEX/LONG_DOUBLE_COMPLEX that expand into C keywords
// (e.g. double _Complex). These break MPICH's mpicxx.h declarations
// (e.g. extern Datatype DOUBLE_COMPLEX;), causing compile errors.
#  ifdef DOUBLE_COMPLEX
#    undef DOUBLE_COMPLEX
#  endif
#  ifdef LONG_DOUBLE_COMPLEX
#    undef LONG_DOUBLE_COMPLEX
#  endif
#  include <mpi.h>
DEAL_II_ENABLE_EXTRA_DIAGNOSTICS
 
#endif
 
 
DEAL_II_NAMESPACE_OPEN
 
#ifndef DEAL_II_WITH_MPI
 
// Without MPI, we would still like to use some constructs with MPI
// data types. Therefore, create some dummies. Since we only ever use
// them inside our own constructs, the right thing to do is to put
// them into namespace dealii:
 
using MPI_Comm     = int;
using MPI_Request  = int;
using MPI_Datatype = int;
using MPI_Op       = int;
 
constexpr MPI_Comm    MPI_COMM_WORLD   = 0;
constexpr MPI_Comm    MPI_COMM_SELF    = 0;
constexpr MPI_Comm    MPI_COMM_NULL    = 0;
constexpr MPI_Request MPI_REQUEST_NULL = 0;
constexpr MPI_Op      MPI_MIN          = 0;
constexpr MPI_Op      MPI_MAX          = 0;
constexpr MPI_Op      MPI_SUM          = 0;
constexpr MPI_Op      MPI_LAND         = 0;
constexpr MPI_Op      MPI_LOR          = 0;
#endif
 
DEAL_II_NAMESPACE_CLOSE
 
#endif