MPI_Dist_graph_neighbors_count  Returns the number of in and out edges for the calling processes in a distributed graph topology and a flag indicating whether the distributed graph is weighted.
#include <mpi.h>
int MPI_Dist_graph_neighbors_count(MPI_Comm comm, int *indegree,
int *outdegree, int *weighted) 
USE MPI
! or the older form: INCLUDE ’mpif.h’
MPI_DIST_GRAPH_NEIGHBORS_COUNT(COMM, INDEGREE, OUTDEGREE, WEIGHTED, IERROR)
INTEGER 
COMM, INDEGREE, OUTDEGREE, IERROR 
LOGICAL WEIGHTED
USE mpi_f08
MPI_Dist_graph_neighbors_count(comm, indegree, outdegree, weighted, ierror)
TYPE(MPI_Comm), INTENT(IN) :: comm 

INTEGER, INTENT(IN) :: indegree, outdegree 

INTEGER, INTENT(OUT) :: weighted 

INTEGER, OPTIONAL, INTENT(OUT) :: ierror 
comm 
Communicator with distributed graph topology (handle). 
indegree 
Number of edges into this process (nonnegative integer). 

outdegree 
Number of edges out of this process (nonnegative integer). 

weighted 
False if MPI_UNWEIGHTED was supplied during creation, true otherwise (logical). 

IERROR 
Fortran only: Error status (integer). 
MPI_Dist_graph_neighbors_count and MPI_Graph_neighbors provide adjacency information for a distributed graph topology. MPI_Dist_graph_neighbors_count returns the number of sources and destinations for the calling process.
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.
Before the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; 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.
MPI_Dist_graph_neighbors