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communicator.hh
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/**
* @file communicator.hh
*
* @author Lars Pastewka <lars.pastewka@imtek.uni-freiburg.de>
*
* @date 07 Mar 2018
*
* @brief abstraction layer for the distributed memory communicator object
*
* Copyright © 2017 Till Junge
*
* µSpectre is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, either version 3, or (at
* your option) any later version.
*
* µSpectre 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
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Emacs; see the file COPYING. If not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#ifndef COMMUNICATOR_H
#define COMMUNICATOR_H
#ifdef WITH_MPI
#include <mpi.h>
#endif
namespace muSpectre {
#ifdef WITH_MPI
template<typename T> decltype(auto) mpi_type() { };
template<> inline decltype(auto) mpi_type<char>() { return MPI_CHAR; }
template<> inline decltype(auto) mpi_type<short>() { return MPI_SHORT; }
template<> inline decltype(auto) mpi_type<int>() { return MPI_INT; }
template<> inline decltype(auto) mpi_type<long>() { return MPI_LONG; }
template<> inline decltype(auto) mpi_type<unsigned char>() {
return MPI_UNSIGNED_CHAR;
}
template<> inline decltype(auto) mpi_type<unsigned short>() {
return MPI_UNSIGNED_SHORT;
}
template<> inline decltype(auto) mpi_type<unsigned int>() {
return MPI_UNSIGNED;
}
template<> inline decltype(auto) mpi_type<unsigned long>() {
return MPI_UNSIGNED_LONG;
}
template<> inline decltype(auto) mpi_type<float>() { return MPI_FLOAT; }
template<> inline decltype(auto) mpi_type<double>() { return MPI_DOUBLE; }
//! lightweight abstraction for the MPI communicator object
class Communicator {
public:
using MPI_Comm_ref = std::remove_pointer_t<MPI_Comm>&;
Communicator(MPI_Comm comm=MPI_COMM_NULL): comm{*comm} {};
~Communicator() {};
//! get rank of present process
int rank() const {
if (&comm == MPI_COMM_NULL) return 0;
int res;
MPI_Comm_rank(&this->comm, &res);
return res;
}
//! get total number of processes
int size() const {
if (&comm == MPI_COMM_NULL) return 1;
int res;
MPI_Comm_size(&this->comm, &res);
return res;
}
//! sum reduction on scalar types
template<typename T>
T sum(const T &arg) const {
if (&comm == MPI_COMM_NULL) return arg;
T res;
MPI_Allreduce(&arg, &res, 1, mpi_type<T>(), MPI_SUM, &this->comm);
return res;
}
MPI_Comm get_mpi_comm() { return &this->comm; }
private:
MPI_Comm_ref comm;
};
#else /* WITH_MPI */
//! stub communicator object that doesn't communicate anything
class Communicator {
public:
Communicator() {};
~Communicator() {};
//! get rank of present process
int rank() const {
return 0;
}
//! get total number of processes
int size() const {
return 1;
}
//! sum reduction on scalar types
template<typename T>
T sum(const T &arg) const { return arg; }
};
#endif
}
#endif /* COMMUNICATOR_H */

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