advanced_research_computing_docker/mpi_bcastcompare.cpp at main · amelialdrew/advanced_research_computing_docker · GitHub

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#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
#include <assert.h>

void my_bcast(void* data, int count, MPI_Datatype datatype, int root,
              MPI_Comm communicator) {
  int world_rank;
  MPI_Comm_rank(communicator, &world_rank);
  int world_size;
  MPI_Comm_size(communicator, &world_size);

  if (world_rank == root) {
    // If we are the root process, send our data to everyone
    int i;
    for (i = 0; i < world_size; i++) {
      if (i != world_rank) {
        MPI_Send(data, count, datatype, i, 0, communicator);
      }
    }
  } else {
    // If we are a receiver process, receive the data from the root
    MPI_Recv(data, count, datatype, root, 0, communicator, MPI_STATUS_IGNORE);
  }
}

int main(int argc, char** argv) {

  int num_elements = 100;
  int num_trials = 10;

  MPI_Init(NULL, NULL);

  int world_rank;
  MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);

  double total_my_bcast_time = 0.0;
  double total_mpi_bcast_time = 0.0;
  int i;
  int* data = (int*)malloc(sizeof(int) * num_elements);
  assert(data != NULL);

  for (i = 0; i < num_trials; i++) {
    // Time my_bcast
    // Synchronize before starting timing
    MPI_Barrier(MPI_COMM_WORLD);
    total_my_bcast_time -= MPI_Wtime();
    my_bcast(data, num_elements, MPI_INT, 0, MPI_COMM_WORLD);
    // Synchronize again before obtaining final time
    MPI_Barrier(MPI_COMM_WORLD);
    total_my_bcast_time += MPI_Wtime();

    // Time MPI_Bcast
    MPI_Barrier(MPI_COMM_WORLD);
    total_mpi_bcast_time -= MPI_Wtime();
    MPI_Bcast(data, num_elements, MPI_INT, 0, MPI_COMM_WORLD);
    MPI_Barrier(MPI_COMM_WORLD);
    total_mpi_bcast_time += MPI_Wtime();
 }

// Print off timing information
    if (world_rank == 0) {
       printf("Data size = %d, Trials = %d\n", num_elements * (int)sizeof(int), num_trials);
       printf("Avg my_bcast time = %lf\n", total_my_bcast_time / num_trials);
       printf("Avg MPI_Bcast time = %lf\n", total_mpi_bcast_time / num_trials);
                           }

       free(data);
       MPI_Finalize();
         }

  // Print off timing information
  //   if (world_rank == 0) {
  //       printf("Data size = %d, Trials = %d\n", num_elements * (int)sizeof(int),
  //                  num_trials);
  //                      printf("Avg my_bcast time = %lf\n", total_my_bcast_time / num_trials);
  //                          printf("Avg MPI_Bcast time = %lf\n", total_mpi_bcast_time / num_trials);
  //                            }
  //
  //                              free(data);
  //                                MPI_Finalize();
  //