NAME

       MPI_Dist_graph_create_adjacent   -  Makes  a  new  communicator  to  which  topology information has been
       attached.

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Dist_graph_create_adjacent(MPI_Comm comm_old, int indegree, const int sources[],
            const int sourceweights[], int outdegree, const int destinations[], const int destweights[],
               MPI_Info info, int reorder, MPI_Comm *comm_dist_graph)

Fortran Syntax

       INCLUDE 'mpif.h'
       MPI_DIST_GRAPH_CREATE_ADJACENT(COMM_OLD, INDEGREE, SOURCES, SOURCEWEIGHTS, OUTDEGREE,
                       DESTINATIONS, DESTWEIGHTS, INFO, REORDER, COMM_DIST_GRAPH, IERROR)
            INTEGER   COMM_OLD, INDEGREE, SOURCES(*), SOURCEWEIGHTS(*), OUTDEGREE, DESTINATIONS(*), DESTWEIGHTS(*), INFO
            INTEGER   COMM_DIST_GRAPH, IERROR
            LOGICAL REORDER

INPUT PARAMETERS

       comm_old  Input communicator without topology (handle).

       indegree  Size of sources and sourceweights arrays (non-negative integer).

       sources   Ranks of 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).

       outdegree Size of destinations and destweights arrays (non-negative integer).

       destinations
                 Ranks of 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).

       Hints on optimization and interpretation of weights (handle).

       reorder   Ranking may be reordered (true) or not (false) (logical).

OUTPUT PARAMETERS

       comm_dist_graph
                 Communicator with distibuted graph topology added (handle).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       MPI_Dist_graph_create_adjacent  creats a new communicator comm_dist_graph with distrubuted graph topology
       and returns a handle to the new communicator. The number of processes in comm_dist_graph is identical  to
       the  number of processes in comm_old. Each process passes all information about its incoming and outgoing
       edges in the virtual distributed graph topology.  The calling processes must ensure that each edge of the
       graph  is  described  in  the  source  and in the destination process with the same weights. If there are
       multiple edges for a given (source,dest) pair, then the sequence of the weights of these edges  does  not
       matter.  The  complete communication topology is the combination of all edges shown in the sources arrays
       of all processes in comm_old, which must be identical to the  combination  of  all  edges  shown  in  the
       destinations arrays. Source and destination ranks must be process ranks of comm_old.  This allows a fully
       distributed specication of the communication graph. Isolated processes (i.e., processes with no  outgoing
       or  incoming  edges,  that is, processes that have specied indegree and outdegree as zero and thus do not
       occur  as  source  or  destination  rank  in  the  graph  specication)   are   allowed.   The   call   to
       MPI_Dist_graph_create_adjacent is collective.

WEIGHTS

       Weights  are specied as non-negative integers and can be used to influence the process remapping strategy
       and other internal MPI optimizations. For instance, approximate count arguments  of  later  communication
       calls along specic edges could be used as their edge weights. Multiplicity of edges can likewise indicate
       more intense communication between pairs of processes. However, the exact meaning of edge weights is  not
       specied  by  the  MPI  standard  and is left to the implementation. An application can supply the special
       value MPI_UNWEIGHTED for the weight array to indicate that all  edges  have  the  same  (effectively  no)
       weight. It is erroneous to supply MPI_UNWEIGHTED for some but not all processes of comm_old. If the graph
       is weighted but indegree or outdegree is zero, then MPI_WEIGHTS_EMPTY  or  any  arbitrary  array  may  be
       passed  to  sourceweights or destweights respectively. Note that MPI_UNWEIGHTED and MPI_WEIGHTS_EMPTY are
       not special weight values; rather they are special values for  the  total  array  argument.  In  Fortran,
       MPI_UNWEIGHTED  and  MPI_WEIGHTS_EMPTY  are  objects  like  MPI_BOTTOM  (not usable for initialization or
       assignment). See MPI-3 § 2.5.4.

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_create MPI_Dist_graph_neighbors MPI_Dist_graph_neighbors_count