lib_mpi_helper.h

/*****************************************************************************
* Multiscale Universal Interface Code Coupling Library                       *
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* Copyright (C) 2019 Y. H. Tang, S. Kudo, X. Bian, Z. Li, G. E. Karniadakis  *
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* ** GNU General Public License, version 3 **                                *
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/**
 * @file lib_mpi_helper.h
 * @author Y. H. Tang
 * @date 1 June 2015
 * @brief MPI data types used internally by MUI.
 */

#ifndef LIB_MPI_HELPER_H_
#define LIB_MPI_HELPER_H_

#include <mpi.h>

namespace mui {

namespace mpi {

template<typename T>
inline MPI_Datatype mpi_type( T              const& t );
inline MPI_Datatype mpi_type( int            const &t ) { return MPI_INT; }
inline MPI_Datatype mpi_type( long           const &t ) { return MPI_LONG; }
inline MPI_Datatype mpi_type( unsigned long  const &t ) { return MPI_UNSIGNED_LONG; }
inline MPI_Datatype mpi_type( long long      const &t ) { return MPI_LONG_LONG; }
inline MPI_Datatype mpi_type( float          const &t ) { return MPI_FLOAT; }
inline MPI_Datatype mpi_type( double         const &t ) { return MPI_DOUBLE; }
inline MPI_Datatype mpi_type( char           const &t ) { return MPI_CHAR; }
inline MPI_Datatype mpi_type( short          const &t ) { return MPI_SHORT; }
inline MPI_Datatype mpi_type( unsigned short const &t ) { return MPI_UNSIGNED_SHORT; }

template<typename T> inline std::vector<T> gather( T t, MPI_Comm comm ) {
	int size, rank;
	MPI_Comm_size( comm, &size );
	MPI_Comm_rank( comm, &rank );
	std::vector<T> v;
	if ( rank == 0 ) v.resize( size );
	MPI_Gather( &t, 1, mpi_type(t), v.data(), 1, mpi_type(t), 0, comm );
	return v;
}

}

}

#endif /* LIB_MPI_HELPER_H_ */