#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include "mpi.h"

#define WITH_PCONTROL 1

int main(int argc, char *argv[])
{
  FILE *fp;
  int iam,numproc;
  int ierr,ncomm;
  int i,j,n;
  int *flags;
  int valin,valout;
  MPI_Group newgroup,world_group;
  MPI_Comm *comm;

  MPI_Init(&argc, &argv);
  MPI_Comm_rank(MPI_COMM_WORLD, &iam);
  MPI_Comm_size(MPI_COMM_WORLD, &numproc);
  MPI_Comm_group(MPI_COMM_WORLD,&world_group);

#if WITH_PCONTROL
  MPI_Pcontrol(0);
#endif

/* Create some communicators, with various processors in them */

  flags = (int *) malloc(numproc*sizeof(int));
  comm = (MPI_Comm *) malloc(2*numproc*sizeof(MPI_Comm));
  comm[0] = MPI_COMM_WORLD;
  for(ncomm=1,i=2; i<numproc-1; i*=2) {
    for(n=j=0; j<numproc; j++)
      if( (float)(j % i) / i < 0.5) 
         flags[n++] = j;
    MPI_Group_incl(world_group, n, flags, &newgroup);
    MPI_Comm_create(MPI_COMM_WORLD,newgroup,comm+ncomm);
    if(comm[ncomm] != MPI_COMM_NULL) {
      ncomm++;
      MPI_Comm_dup(comm[ncomm-1],comm+ncomm);
      ncomm++;
    }
  }
  for(i=0; i<iam; i++)
    valin = random();
  for(i=1; i<ncomm/2; i++) MPI_Comm_free(comm+i);
#if WITH_PCONTROL
  MPI_Pcontrol(1);
#endif
  for( ; i < ncomm; i++) {
    valin = random();
    MPI_Allreduce(&valin,&valout,1,MPI_INTEGER,MPI_MAX,comm[i]);
    printf("%d: %d %d\n",iam,valin,valout);
    MPI_Comm_free(comm+i);
  }
  MPI_Finalize();
}