Groups. A group contains processes belonging to an application

MPI_GROUP_EMPTY

int MPI_Group_size (MPI_Group group, int *size);
int MPI_Group_rank (MPI_Group group, int *rank);

int MPI_Group_translate_ranks (
    MPI_Group group1, int n, const int ranks1 [],
    MPI_Group group2, int ranks2 []);

int MPI_Group_compare (MPI_Group group1, MPI_Group group2, int *result);

int MPI_Group_union (MPI_Group group1, MPI_Group group2, MPI_Group *newgroup);
int MPI_Group_difference (MPI_Group group1, MPI_Group group2, MPI_Group *newgroup);
int MPI_Group_intersection (MPI_Group group1, MPI_Group group2, MPI_Group *newgroup);

int MPI_Group_incl (MPI_Group group, int n, const int ranks [], MPI_Group *newgroup);
int MPI_Group_excl (MPI_Group group, int n, const int ranks [], MPI_Group *newgroup);
int MPI_Group_range_incl (MPI_Group group, int n, int ranges [][3], MPI_Group *newgroup);
int MPI_Group_range_excl (MPI_Group group, int n, int ranges [][3], MPI_Group *newgroup);

int MPI_Comm_group (MPI_Comm comm, MPI_Group *group);

int MPI_Group_from_session_pset (MPI_Session session, const char *pset_name, MPI_Group *newgroup);

int MPI_Group_free (MPI_Group *group);

Communicators. A communicator represents one or two groups in communication context

MPI_COMM_SELF
MPI_COMM_WORLD

int MPI_Comm_size (MPI_Comm comm, int *size);
int MPI_Comm_rank (MPI_Comm comm, int *rank);

int MPI_Comm_compare (MPI_Comm comm1, MPI_Comm comm2, int *result);

int MPI_Comm_dup (MPI_Comm comm, MPI_Comm *newcomm);
int MPI_Comm_dup_with_info (MPI_Comm comm, MPI_Info info, MPI_Comm *newcomm);

int MPI_Comm_create (MPI_Comm comm, MPI_Group group, MPI_Comm *newcomm);
int MPI_Comm_create_group (MPI_Comm comm, MPI_Group group, int tag, MPI_Comm *newcomm);
int MPI_Comm_create_from_group (MPI_Group group, const char *stringtag, MPI_Info info, MPI_Errhandler errhandler, MPI_Comm *newcomm);
int MPI_Intercomm_create (
    MPI_Comm local_comm, int local_leader,
    MPI_Comm peer_comm, int remote_leader,
    int tag, MPI_Comm *newintercomm);
int MPI_Intercomm_create_from_groups (
    MPI_Group local_group, int local_leader,
    MPI_Group remote_group, int remote_leader,
    const char *stringtag, MPI_Info info, MPI_Errhandler errhandler, MPI_Comm *newintercomm);

int MPI_Comm_split (MPI_Comm comm, int color, int key, MPI_Comm *newcomm);
int MPI_Comm_split_type (MPI_Comm comm, int split_type, int key, MPI_Info info, MPI_Comm *newcomm);

int MPI_Intercomm_merge (MPI_Comm intercomm, int high, MPI_Comm *newintracomm);

int MPI_Comm_free (MPI_Comm *comm);

int MPI_Comm_set_info (MPI_Comm comm, MPI_Info info);
int MPI_Comm_get_info (MPI_Comm comm, MPI_Info *info_used);

int MPI_Comm_test_inter (MPI_Comm comm, int *flag);
int MPI_Comm_remote_size (MPI_Comm comm, int *size);
int MPI_Comm_remote_group (MPI_Comm comm, MPI_Group *group);