mpi_test.cpp

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#include <time.h>
#include <stdlib.h>
#include <stdio.h>
#include <mpi.h>
#include <math.h>

int main(int argc, char *argv[]) {
  int numprocs, rank, namelen;
  char processor_name[MPI_MAX_PROCESSOR_NAME];

  MPI::Init(argc, argv);
  //MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
  //MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  rank = MPI::COMM_WORLD.Get_rank();
  numprocs = MPI::COMM_WORLD.Get_size();
  MPI::Get_processor_name(processor_name, namelen);

  //printf("Process %d on %s out of %d\n", rank, processor_name, numprocs);

  // init random seed
  srand(time(NULL)+rank);

  double start_time = MPI::Wtime();
  // simple summing test
  for (unsigned int k = 1; k < 8; k++)
  {
    unsigned int nx = pow(10,k);
    for (int target=0; target < MPI::COMM_WORLD.Get_size(); target++)
    {
      if (rank == target)
      {
        double sum = 0;
        for (int i=0; i < MPI::COMM_WORLD.Get_size(); i++)
        {
          // receive from all other nodes
          if (i != target)
          {
            double comm_time = MPI::Wtime();
            MPI::Status status;
            MPI::COMM_WORLD.Probe (i, target, status);      // for test purposes only
            // Gets the number of "top level" elements
            unsigned int count = status.Get_count (MPI_BYTE);
            double *buf = (double*)malloc (count * sizeof (double));
            // Performs a standard-mode blocking receive
            //printf("debug %d count %d\n",i,count);
            MPI::COMM_WORLD.Recv (buf, count, MPI_DOUBLE, i, target, status);
            printf("receive: from %d to %d on %s szie %d complete at %f duration %f\n",i,rank,processor_name,nx,MPI::Wtime()-start_time,MPI::Wtime()-comm_time);
            for (unsigned int j=0;j<count;j++) sum += buf[j];
            free(buf);
          }
        }
        printf("sum: %f\n",sum);
      }
      else
      {
        // send to target
        double *x = (double*)malloc (nx * sizeof (double));
        for (unsigned int j=0;j<nx;j++) x[j] = (double)rand()/(double)RAND_MAX;
        double comm_time = MPI::Wtime();
        MPI::COMM_WORLD.Send(x, nx, MPI_DOUBLE , target, target);
        printf("send: from %d to %d on %s size %d complete at %f duration %f\n",rank,target,processor_name,nx,MPI::Wtime()-start_time,MPI::Wtime()-comm_time);
        free(x);
      }
    }
  }

  MPI::Finalize();
}