operators.hpp

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// Copyright (c) 2024 Simons Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0.txt
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Authors: Thomas Hahn, Alexander Hampel, Olivier Parcollet, Nils Wentzell
 
#pragma once
 
#include "./utils.hpp"
 
#include <mpi.h>
 
namespace mpi {
 
  template <typename T, T (*F)(T const &, T const &)> MPI_Op map_C_function() {
    MPI_Op myOp{};
    MPI_User_function *map_function = +[](void *in, void *inout, int *len, MPI_Datatype *) { // NOLINT (MPI_Op_create needs a non-const pointer)
      auto *inT    = static_cast<T *>(in);
      auto *inoutT = static_cast<T *>(inout);
      for (int i = 0; i < *len; ++i, ++inT, ++inoutT) { *inoutT = F(*inoutT, *inT); }
    };
    check_mpi_call(MPI_Op_create(map_function, true, &myOp), "MPI_Op_create");
    return myOp;
  }
 
  namespace detail {
    // Generic addition. FIXME Convert to lambda, requires gcc 13.2+
    template <typename T> T generic_add(T const &lhs, T const &rhs) { return lhs + rhs; }
  } // namespace detail
 
  template <typename T> MPI_Op map_add() { return map_C_function<T, detail::generic_add>(); }
 
} // namespace mpi