CommSplitter.h

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//
// Class CommSplitter
//   Role assignment according to strategy (that might use hardware
//   network information).
//
//   The CommSplitter splits the passed (usually MPI_COMM_WORLD) communicator
//   into several comm groups using the colors provided by the splitting
//   strategy.
//   After construction each processor has an assigned role (optimizer, worker
//   or pilot) and a set of communicators to send and receive tasks.
//   The expected colors have the following meaning:
//     - color[0] is shared by all my co-workers
//     - color[1] is shared by the optimizer leader and the pilot
//     - color[2] is shared by the worker leader and the pilot
//     - color[3] is shared by all processors with the same role (used for
//       broadcasts)
//
// Copyright (c) 2010 - 2013, Yves Ineichen, ETH Zürich
// All rights reserved
//
// Implemented as part of the PhD thesis
// "Toward massively parallel multi-objective optimization with application to
// particle accelerators" (https://doi.org/10.3929/ethz-a-009792359)
//
// This file is part of OPAL.
//
// OPAL 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.
//
// You should have received a copy of the GNU General Public License
// along with OPAL. If not, see <https://www.gnu.org/licenses/>.
//
#ifndef __COMM_SPLITTER__
#define __COMM_SPLITTER__
 
#include "mpi.h"
 
#include "Comm/types.h"
#include "Util/Types.h"
#include "Util/CmdArguments.h"
#include "Util/OptPilotException.h"
 
//TODO: what is the performance difference between using MPI_COMM_WORLD and
//      p2p communication vs. communicator groups??
template< class Strategy_t >
class CommSplitter : public Strategy_t {
 
public:
 
    CommSplitter(CmdArguments_t args, MPI_Comm comm = MPI_COMM_WORLD)
        : Strategy_t(args, comm)
        , world_comm_(comm)
    {
        MPI_Comm_group(world_comm_, &world_group_);
        MPI_Comm_rank(world_comm_,  &global_rank_);
 
        // the splitter strategy computes the colorings
        Strategy_t::split();
 
        my_opt_comm_      = MPI_COMM_NULL;
        my_worker_comm_   = MPI_COMM_NULL;
        my_coworker_comm_ = MPI_COMM_NULL;
 
 
        MPI_Comm_split(world_comm_, Strategy_t::colorings_[0],
                       global_rank_, &my_coworker_comm_ );
 
        MPI_Comm_split(world_comm_, Strategy_t::colorings_[1],
                       global_rank_, &my_opt_comm_ );
 
        MPI_Comm_split(world_comm_, Strategy_t::colorings_[2],
                       global_rank_, &my_worker_comm_ );
 
        MPI_Comm_split(world_comm_, Strategy_t::colorings_[3],
                       global_rank_, &my_comm_world_ );
 
        // just a precaution to make sure everybody is ready
        MPI_Barrier(world_comm_);
    }
 
    virtual ~CommSplitter()
    {
        MPI_Group_free(&world_group_);
        if(world_comm_ != MPI_COMM_WORLD)
            MPI_Comm_free(&world_comm_);
    }
 
    bool isOptimizer() const { return Strategy_t::role_ == OPTIMIZER; }
    bool isWorker()    const { return Strategy_t::role_ == WORKER; }
    bool isPilot()     const { return Strategy_t::role_ == POLLER; }
 
    MPI_Comm mpiComm() const { return world_comm_; }
    int globalRank()   const { return global_rank_; }
    int pilotRank()    const { return Strategy_t::poller_; }
    int getLeader()    const { return Strategy_t::leader_; }
 
    int getNrWorkerGroups() const { return Strategy_t::getNrWorkerGroups();}

    Comm::Bundle_t getBundle() const {
 
        Comm::Bundle_t bundle;
 
        bundle.island_id        = Strategy_t::group_id_;
 
        bundle.leader_pid       = Strategy_t::leader_;
        bundle.master_pid       = Strategy_t::poller_;
        //FIXME: is it always 0?
        bundle.master_local_pid = 0; //poller_local_pid_;
 
        bundle.worker           = my_worker_comm_;
        bundle.opt              = my_opt_comm_;
        bundle.coworkers        = my_coworker_comm_;
        bundle.world            = my_comm_world_;
 
        return bundle;
    }
 
private:
 
    MPI_Comm  world_comm_;
    MPI_Group world_group_;

    int global_rank_;
 
    // define various communicators for communication between components
    MPI_Comm my_worker_comm_;
    MPI_Comm my_opt_comm_;
    MPI_Comm my_coworker_comm_;
    MPI_Comm my_comm_world_;

    int poller_local_pid_;
};
 
#endif