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