/*****************************************************************/               /*****************************************************************/
/*                                                               */               /*                                                               */
/* Petit programme minimal en MPI                                */            £  /* Utilisation du broadcast offert par la librairie MPI...       */
/*                                                               */               /*                                                               */
/*****************************************************************/               /*****************************************************************/
#include <stdlib.h>                                                               #include <stdlib.h>
#include <stdio.h>                                                                #include <stdio.h>
#include <unistd.h>                                                               #include <unistd.h>
#include <mpi.h>                                                                  #include <mpi.h>
#include <sys/time.h>                                                             #include <sys/time.h>

#define BUFLEN 65536                                                              #define BUFLEN 65536

long ms_time()                                                                    long ms_time() 
{                                                                                 {
  struct timeval tv;                                                                struct timeval tv;

  gettimeofday(&tv, NULL);                                                          gettimeofday(&tv, NULL);
  return(tv.tv_sec*1000 + tv.tv_usec/1000);                                         return(tv.tv_sec*1000 + tv.tv_usec/1000);
}                                                                                 }

void long_computation()                                                           void long_computation() 
{                                                                                 {
   long now=ms_time();                                                               long now=ms_time();
   while(ms_time()<now+4000)                                                         while(ms_time()<now+4000) 
     {                                                                                 {
     }                                                                                 }
}                                                                                 }

int main(int argc, char **argv)                                                   int main(int argc, char **argv) 
{                                                                                 {
  int nb_proc;                                                                      int nb_proc;
  int my_id;                                                                        int my_id;
                                                                               µ    int next;
  int buffer[BUFLEN];                                                               int buffer[BUFLEN];

                                                                               µ    long start,end;
                                                                               µ
  MPI_Init(&argc,&argv);                                                            MPI_Init(&argc,&argv);
  MPI_Comm_size(MPI_COMM_WORLD,&nb_proc);                                           MPI_Comm_size(MPI_COMM_WORLD,&nb_proc);
  MPI_Comm_rank(MPI_COMM_WORLD,&my_id);                                             MPI_Comm_rank(MPI_COMM_WORLD,&my_id);
 
  printf("Je suis le processus P%d et nous sommes %d au total.\n",             £    if (my_id == nb_proc-1)
         my_id, nb_proc);                                                      £      next = 0;
                                                                               µ    else
                                                                               µ      next = my_id+1;
                                                                               µ
                                                                               µ    if (my_id == 0) start = ms_time();
                                                                               µ
                                                                               µ    if (my_id == 0) 
                                                                               µ      {
                                                                               µ        int i;
                                                                               µ        for(i=0; i<BUFLEN; i++) buffer[i]=i;
                                                                               µ      } 
                                                                               µ
                                                                               µ    MPI_Bcast(buffer, BUFLEN, MPI_INT, 0, MPI_COMM_WORLD);
                                                                               µ    long_computation();

  MPI_Finalize();                                                                   MPI_Finalize();
                                                                               µ    if (my_id == 0) end = ms_time();
                                                                               µ    if (my_id == 0) printf("Ça m'a prit %ld ms\n",(end-start));

  return (0);                                                                       return (0);
}                                                                                 }