/*****************************************************************/
/*                                                               */
/* Petit programme minimal en MPI                                */
/*                                                               */
/*****************************************************************/
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <mpi.h>
#include <sys/time.h>

#define BUFLEN 10

long ms_time(void) 
{
  struct timeval tv;

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

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

int main(int argc, char **argv) 
{
  int nb_proc;
  int my_id, i, j;
  int bufferS[BUFLEN];
  int * bufferR;

  MPI_Init(&argc,&argv);
  MPI_Comm_size(MPI_COMM_WORLD,&nb_proc);
  MPI_Comm_rank(MPI_COMM_WORLD,&my_id);

  for (i = 0; i < BUFLEN; ++ i)
    bufferS[i] = my_id;

  bufferR = malloc(sizeof(int) * nb_proc * BUFLEN);

 
  printf("Je suis le processus P%d et nous sommes %d au total.\n",
	 my_id, nb_proc);

  MPI_Allgather(bufferS, BUFLEN, MPI_INT,
		bufferR, BUFLEN, MPI_INT, MPI_COMM_WORLD);

  if (my_id == 0) {
    printf("Result all gather:\n");
    for (i = 0; i < BUFLEN * nb_proc; ++ i)
      printf("%d ", bufferR[i]);
    printf("\n");
  }
  free(bufferR);

  bufferR = malloc(sizeof(int) * BUFLEN);

  /* La taille des donnees envoyees est ce que tu envoies
   * a chaque processeur et non la taille totale des donnees,
   * idem en reception
   */
  MPI_Alltoall(bufferS, BUFLEN / nb_proc, MPI_INT,
	       bufferR, BUFLEN / nb_proc, MPI_INT, MPI_COMM_WORLD);

  for (j = 0; j < nb_proc; ++ j) {
    if (my_id == j) {
      printf("Result all to all for processor %d:\n", j);
      for (i = 0; i < BUFLEN; ++ i)
	printf("%d ", bufferR[i]);
      printf("\n");
    }
    MPI_Barrier(MPI_COMM_WORLD);
  }
  free(bufferR);


  MPI_Finalize();


  return (0);
}