#include #include /* Creates new communicators by "splitting" a communicator into a group of sub-communicators based on the input values color and key. MPI_Comm_split( MPI_Comm comm, //communicator to split int color, //determines to which new communicator each process will belong. Same color same communicator int key, //determ the order(rank) within each new communicator. The smallest key value is assigned to 0, next to 1 and so on MPI_Comm* newcomm //new communicator ) */ int main(int argc, char* argv[]) { MPI_Init(NULL, NULL); //Initialize the MPI environment int world_size; MPI_Comm_size(MPI_COMM_WORLD, &world_size); //Get the number of processes int world_rank; MPI_Comm_rank(MPI_COMM_WORLD, &world_rank); //Get the number of process //In the following code we suppose to have 10 processes and we want to split them in sub groups "rows" as they are a 2x5 Matrix int color = world_rank / 2; //Determine color based on row MPI_Comm row_comm; //To free //MPI_Comm_split(comm, color, key, newcomm) MPI_Comm_split(MPI_COMM_WORLD, color, -world_rank, &row_comm); int row_size; MPI_Comm_size(row_comm, &row_size); //Get the number of processes related to the communicator int row_rank; MPI_Comm_rank(row_comm, &row_rank); //Get the number of process related to the communicator std::cout << "Process (rank " << world_rank+1 << "/" << world_size << ") is splitted to sub-group " << row_rank+1 << "/" << row_size << "-" << color << " (row/size-color)" << std::endl; MPI_Comm_free(&row_comm); //We have to free the communicator that we created above MPI_Finalize(); //Clean up the MPI environment return 0; }