int leader_root, leader_of_root = -1;
MPI_Comm shmem_comm, leader_comm;
//if not set (use of the algo directly, without mvapich2 selector)
int leader_root, leader_of_root = -1;
MPI_Comm shmem_comm, leader_comm;
//if not set (use of the algo directly, without mvapich2 selector)