G4MPIutils.cc File Reference

#include "G4MPIutils.hh"
#include <iostream>
#include <cstdlib>
#include <algorithm>
#include <functional>
#include <assert.h>
#include <utility>
#include "globals.hh"

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Functions
int	_testMe (int argc, char **argv)

Function Documentation

int _testMe	(	int	argc,
		char **	argv
	)

Definition at line 93 of file G4MPIutils.cc.

                                  {
  using namespace G4mpi;
  unsigned int worldSize = 10;
  if ( argc > 1 ) worldSize = atoi(argv[1]);
  unsigned int myRank = worldSize-1;
  if ( argc > 2 ) myRank = atoi(argv[2]);
  std::cout<<"World size: "<<worldSize<<std::endl;

  assert( myRank < worldSize);
  //MPI function stubs
  auto MPI_Receive = [](const rank_t& s, const rank_t& r) {
    std::cout<<"MPI_Receive from: "<<s<<" to "<<r<<std::endl;
    return 0;
  };
  auto MPI_Send = [](const rank_t& s, const rank_t& r) {
    std::cout<<"MPI_Send from: "<<s<<" to "<<r<<std::endl;;
    return 0;
  };
  auto MPI_Barrier = [] {
    std::cout<<"MPI_Barrier"<<std::endl;
    return 0;
  };

  //Build the initial network of ranks
  std::vector<rank_t> ranks(worldSize);
  for ( unsigned int i = 0 ; i<worldSize ; ++i ) {
    if ( i != 2 )
      { ranks.push_back(i);
      } else {
      ranks.push_back(i);
      ranks.push_back(i);
    }
  }
  //Remove duplicates
  ranks.erase( std::unique(ranks.begin(),ranks.end()),ranks.end());
  
  //Optimize network trafic
  if ( ranks.size() == 1 ) {
    std::cout<<"only one rank, nothing to do"<<std::endl;
    return 0;
  }
  auto comms = G4mpi::buildCommunicationMap( ranks );
  assert( ranks.size() == 1 && ranks[0] == 0 );

  std::cout<<"Communiction Map (size: "<<comms.size()<<"):"<<std::endl;
  for ( const auto& x : comms ) {
    std::cout<<"Cycle "<<x.first<<": ";
    for ( const auto& y : x.second ) {
      std::cout<<y.first<<"->"<<y.second<<", ";
    }
    std::cout<<std::endl;
  }

  std::cout<<"Simulate communication pattern for rank: "<<myRank<<std::endl;
  for (const auto& x: comms ) {
    std::cout<<"Cycle "<<x.first<<std::endl;
    for ( const auto& y : x.second ) {
      if ( myRank == y.first ) { MPI_Send(y.first,y.second); }
      else if ( myRank == y.second ) { MPI_Receive(y.first,y.second); }
    }
    //Important: Wait for this cycle to end before going to the next, even if
    //this rank did not do anything
    //This is needed to be sure that the redcutions are done correctly
    MPI_Barrier();
  }
  return 0;
}

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