comm_mpi.h

/*
Multiscale Universal Interface Code Coupling Library

Copyright (C) 2017 Y. H. Tang, S. Kudo, X. Bian, Z. Li, G. E. Karniadakis

This software is jointly licensed under the Apache License, Version 2.0
and the GNU General Public License version 3, you may use it according
to either.

** Apache License, version 2.0 **

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

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.

** GNU General Public License, version 3 **

This program 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 of the License, or
(at your option) any later version.

This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.

** File Details **

Filename: comm_mpi.h
Created: Feb 11, 2014
Author: S. Kudo
Description:
*/

#ifndef COMM_MPI_H_
#define COMM_MPI_H_

#include <mpi.h>
#include "comm.h"
#include "util.h"
#include "lib_uri.h"

namespace mui {

/*
 * MPI base implementation of Comm
 */

class comm_mpi : public communicator {
public:
	comm_mpi(const char URI[], MPI_Comm world ) :
		domain_local_(0), domain_remote_(0),
		local_size_(0), local_rank_(0), remote_size_(0), global_size_(0), global_rank_(0),
		initialized(false), init_by_me(false) {
		init(URI, world);
	}
	virtual ~comm_mpi() {
		finalize();
	}

	void init( const char URI[], MPI_Comm world ) {
		if ( initialized ) {
			throw( std::runtime_error("duplicate MUI communicator initialization") );
		}

		// check MPI initialization status
		int init;
		MPI_Initialized( &init );
		if (!init) {
			init_by_me = true;
			MPI_Init( NULL, NULL );
		}

		// duplicate world to avoid potential conflict with host program
		if (world == MPI_COMM_WORLD) MPI_Comm_dup( MPI_COMM_WORLD, &world );
		MPI_Comm_size( world, &global_size_ );
		MPI_Comm_rank( world, &global_rank_ );
		if (global_size_ < 2) {
			fprintf( stderr, "WARNING: # of global ranks less than 2\n" );
		}

		// get upper bond for tag hash
		int prime;
		{
			int* v;
			int flag;
			MPI_Comm_get_attr(MPI_COMM_WORLD,MPI_TAG_UB,&v,&flag);
			prime = *v;
		}

		// parse URI, split the world using domain tag
		uri desc(URI);
		int domain_hash = std::hash<std::string>()( desc.host() );
		domain_hash=std::abs(domain_hash);
		int ifs_hash    = std::hash<std::string>()( desc.path() );
		ifs_hash=std::abs(ifs_hash);
		MPI_Comm_split( world, domain_hash % prime, global_rank_, &domain_local_ );
		MPI_Comm_size( domain_local_, &local_size_ );
		MPI_Comm_rank( domain_local_, &local_rank_ );

		// set intercommunication using interface tag
		std::vector<int> all_domain( global_size_, 0 );
		std::vector<int> all_ifs   ( global_size_, 0 );
		MPI_Allgather( &domain_hash, 1, MPI_INT, &all_domain[0], 1, MPI_INT, world );
		MPI_Allgather( &ifs_hash,    1, MPI_INT, &all_ifs[0],    1, MPI_INT, world );
		for(int i = 0 ; i < global_size_ ; i++) {
			if ( i == global_rank_ ) continue;
			if ( all_domain[i] != domain_hash && all_ifs[i] == ifs_hash ) {
				MPI_Intercomm_create( domain_local_, 0, world, i, ifs_hash % prime, &domain_remote_ );
				break;
			}
		}
		MPI_Comm_remote_size( domain_remote_, &remote_size_ );

		// output for debugging
		for(int i=0;i<global_size_;i++) {
			if ( i == global_rank_ )
				std::cout	<<"rank "<<global_rank_<<'\t'
							<<"identifier "<<URI<<'\t'
							<<"domain size "<<local_size_<<'\t'
							<<"peer number "<<remote_size_<<'\t'
							<<std::endl;
			MPI_Barrier( world );
		}

		initialized = true;
	}

	void finalize() {
		if ( initialized && init_by_me ) MPI_Finalize();
	}

	virtual int local_size() const { return local_size_; }
	virtual int local_rank() const { return local_rank_; }
	virtual int remote_size() const { return remote_size_; }
	virtual int global_size() const { return global_size_; }
	virtual int global_rank() const { return global_rank_; }

protected:
	MPI_Comm domain_local_;
	MPI_Comm domain_remote_;
	int local_size_;
	int local_rank_;
	int remote_size_;
	int global_size_;
	int global_rank_;
private:
	bool initialized, init_by_me;
};

}

#endif