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**NAME**

MPI_Dist_graph_neighbors- Returns the neighbors of the calling process in a distributed graph topology.

**SYNTAX**

**C** **Syntax**

#include <mpi.h> int MPI_Dist_graph_neighbors(MPI_Commcomm, intmaxindegree, intsources[], intsourceweights[], intmaxoutdegree, intdestinations[], intdestweights[])

**Fortran** **Syntax**

INCLUDE 'mpif.h' MPI_DIST_GRAPH_NEIGHBORS(COMM, MAXINDEGREE, SOURCES, SOURCEWEIGHTS, MAXOUTDEGREE, DESTINATIONS, DESTWEIGHTS, IERROR) INTEGER COMM, MAXINDEGREE, SOURCES(*), SOURCEWEIGHTS(*), MAXOUTDEGREE, DESTINATIONS(*), DESTWEIGHTS(*), IERROR

**INPUT** **PARAMETERS**

comm Communicator with distributed graph topology (handle). maxindegree Size ofsourcesandsourceweightsarrays (non-negative integer). maxoutdegree Size ofdestinationsanddestweightsarrays (non-negative integer).

**OUTPUT** **PARAMETERS**

sources Processes for which the calling process is a destination (array of non-negative integers). sourceweights Weights of the edges into the calling process (array of non-negative integers). destinations Processes for which the calling process is a source (array of non-negative integers). destweights Weights of the edges out of the calling process (array of non-negative integers). IERROR Fortran only: Error status (integer).

**DESCRIPTION**

MPI_Dist_graph_neighbors returns the source and destination ranks in a distributed graph topology for the calling process. This call will return up tomaxindegreesource ranks in thesourcesarray and up tomaxoutdegreedestination ranks in thedestinationsarray. If weights were specified at the time of the communicator's creation then the associated weights are returned in thesourceweightsanddestweightsarrays. If the communicator was created with MPI_Dist_graph_create_adjacent then the order of the values insourcesanddestinationsis identical to the input that was used by the process with the same rank in comm_old in the creation call.

**ERRORS**

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.

**SEE** **ALSO**

MPI_Dist_graph_neighbors_count