BLMPI.hh

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//      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