//	BLMPI.hh -- MPI interface for parallelization
/*
This source file is part of G4beamline, http://g4beamline.muonsinc.com
Copyright (C) 2003,2004,2005,2006 by Tom Roberts, all rights reserved.

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 2
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.

http://www.gnu.org/copyleft/gpl.html
*/

#ifndef BLMPI_HH
#define BLMPI_HH

/**	class BLMPI implements MPI interface for parallelization.
 *
 *	BLMPI handles G4beamline-specific MPI stuff.
 *
 *	NOTE: No other class should call any MPI functions directly. This
 *	implies that the only #include <mpi.h> should be in BLMPI.cc.
 *
 *	NOTE: When running in MPI mode, threads are not permitted.
 *
 *	When running under MPI, all BLNTuples are physically written
 *	only by the rank-0 instance; MPI is used by all other instances to
 *	send messages to rank-0 to create BLNTuple-s and to append rows to
 *	BLNTuple-s.
 *
 *	This entire class is static.
 **/
class BLMPI {
	static int rank;
	static int nodes;
	static void mainRankZero();
	static void mainRankNonZero();
	static int nComplete;
	static double startupTime;
	static double startupWaitTime;
	static double computeTime;
	static double computeWaitTime;
public:
	/// init() will check whether or not we are running under MPI,
	/// and will initialize MPI if so. 
	/// MUST be called before any other BLMPI routine.
	/// NOTE: for all but rank-0, sets stdout to /dev/null (stderr
	/// remains connected for all ranks, so G4Exception will be seen).
	static void init(int *argc, char ***argv);

	/// isMPI() returns true if in MPI mode.
	static bool isMPI();

	/// isRank0() returns false in non-MPI mode, and returns true if
	/// this node is rank 0 in MPI.
	static bool isRank0();

	/// isRank1() returns true in non-MPI mode, and returns true if
	/// this node is rank 1 in MPI. Used for Traces and other things
	/// that should happen once per simulation, not once per node.
	static bool isRank1();

	/// main will perform the computation in MPI mode.
	/// In non-MPI mode this is a no-op that returns immediately.
	/// In MPI mode this determines the collective/serial mode and then
	/// performs the computation, never returning.
	static void main();
};

#endif // BLMPI_HH