lab3_benchmark.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <mpi.h>

#define VECSIZE 8
#define ITERATIONS 10000
double When()
{
  struct timeval tp;
  gettimeofday(&tp, NULL);
  return ((double) tp.tv_sec + (double) tp.tv_usec * 1e-6);
}
main(int argc, char *argv[])
{
        int iproc, nproc,i, iter;
        char host[255], message[55];
        MPI_Status status;

        MPI_Init(&argc, &argv);
        MPI_Comm_size(MPI_COMM_WORLD, &nproc);
        MPI_Comm_rank(MPI_COMM_WORLD, &iproc);

        gethostname(host,253);
        printf("I am proc %d of %d running on %s\n", iproc, nproc,host);
        // each process has an array of VECSIZE double: ain[VECSIZE]
        double ain[VECSIZE], aout[VECSIZE];
        int  ind[VECSIZE];
        struct {
            double val;
            int   rank;
        } in[VECSIZE], out[VECSIZE];
        int myrank, root = 0;

        MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
        // Start time here
        srand(myrank+5);
        double start = When();
        for(iter = 0; iter < ITERATIONS; iter++) {
          for(i = 0; i < VECSIZE; i++) {
            ain[i] = rand();
//          printf("init proc %d [%d]=%f\n",myrank,i,ain[i]);
          }
          for (i=0; i<VECSIZE; ++i) {
            in[i].val = ain[i];
            in[i].rank = myrank;
          }
          MPI_Reduce( in, out, VECSIZE, MPI_DOUBLE_INT, MPI_MAXLOC, root, MPI_COMM_WORLD);
          // At this point, the answer resides on process root
          if (myrank == root) {
              /* read ranks out
               */
              for (i=0; i<VECSIZE; ++i) {
//                printf("root out[%d] = %f from %d\n",i,out[i].val,out[i].rank);
                  aout[i] = out[i].val;
                  ind[i] = out[i].rank;
              }
          }
          // Now broadcast this max vector to everyone else.
          MPI_Bcast(out, VECSIZE, MPI_DOUBLE_INT, root, MPI_COMM_WORLD);
          for(i = 0; i < VECSIZE; i++) {
//          printf("final proc %d [%d]=%f from %d\n",myrank,i,out[i].val,out[i].rank);
          }
        }
        MPI_Finalize();
        double end = When();
        if(myrank == root) {
          printf("Time %f\n",end-start);
        }
}