Returns the number of neighbors of a node associated with a graph topology
int MPI_Graph_neighbors_count(MPI_Comm comm, int rank, int *nneighbors)
- communicator with graph topology (handle)
- rank of process in group of comm (integer)
- number of neighbors of specified process (integer)
Thread and Interrupt Safety
This routine is both thread- and interrupt-safe.
This means that this routine may safely be used by multiple threads and
from within a signal handler.
Notes for Fortran
All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have
an additional argument ierr at the end of the argument list. ierr
is an integer and has the same meaning as the return value of the routine
in C. In Fortran, MPI routines are subroutines, and are invoked with the
All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER
All MPI routines (except MPI_Wtime and MPI_Wtick) return an error value;
C routines as the value of the function and Fortran routines in the last
argument. Before the value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job. The error handler
may be changed with MPI_Comm_set_errhandler (for communicators),
MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for
RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but
its use is deprecated. The predefined error handler
MPI_ERRORS_RETURN may be used to cause error values to be returned.
Note that MPI does not guarantee that an MPI program can continue past
an error; however, MPI implementations will attempt to continue whenever
- No error; MPI routine completed successfully.
- Invalid topology. Either there is no topology
associated with this communicator, or it is not the correct type (e.g.,
MPI_CART when expecting MPI_GRAPH).
- Invalid communicator. A common error is to use a null
communicator in a call (not even allowed in MPI_Comm_rank).
- Invalid argument. Some argument is invalid and is not
identified by a specific error class (e.g., MPI_ERR_RANK).
- Invalid source or destination rank. Ranks must be between
zero and the size of the communicator minus one; ranks in a receive
(MPI_Recv, MPI_Irecv, MPI_Sendrecv, etc.) may also be MPI_ANY_SOURCE.