/*****************************************************************/               /*****************************************************************/
/*                                                               */            £  /* Mise en oeuvre d'un broadcast en MPI à la main avec des       */
/* Utilisation du broadcast offert par la librairie MPI...       */            £  /* primitives de communications bloquantes.                      */
/*                                                               */               /*                                                               */
/*****************************************************************/               /*****************************************************************/
#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;
  int next;                                                                         int next;
  int buffer[BUFLEN];                                                               int buffer[BUFLEN];
                                                                               µ    MPI_Status status;

  long start,end;                                                                   long start,end;

  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);

  if (my_id == nb_proc-1)                                                           if (my_id == nb_proc-1)
    next = 0;                                                                         next = 0;
  else                                                                              else
    next = my_id+1;                                                                   next = my_id+1;

  if (my_id == 0) start = ms_time();                                                if (my_id == 0) start = ms_time();

  if (my_id == 0)                                                                   if (my_id == 0) 
    {                                                                                 {
      int i;                                                                            int i;
      for(i=0; i<BUFLEN; i++) buffer[i]=i;                                              for(i=0; i<BUFLEN; i++) buffer[i]=i;
                                                                               µ        
                                                                               µ        MPI_Send(buffer, BUFLEN, MPI_INT, next, 666, MPI_COMM_WORLD);
                                                                               µ      } 
                                                                               µ    else 
                                                                               µ      {
                                                                               µ        MPI_Recv(buffer, BUFLEN, MPI_INT, MPI_ANY_SOURCE, 666, MPI_COMM_WORLD,
                                                                               µ                 &status);
                                                                               µ        
                                                                               µ        if (my_id != nb_proc-1)
                                                                               µ          MPI_Send(buffer, BUFLEN, MPI_INT, next, 666, MPI_COMM_WORLD);
    }                                                                                 }

  MPI_Bcast(buffer, BUFLEN, MPI_INT, 0, MPI_COMM_WORLD);                       ¢---
  long_computation();                                                               long_computation();

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

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