MPI_Dist_graph_create_adjacent(3) Open MPI MPI_Dist_graph_create_adjacent(3)NAMEMPI_Dist_graph_create_adjacent - Makes a new communicator to which
topology information has been attached.
SYNTAXC 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 inte‐
ger).
sources Ranks of processes for which the calling process is a desti‐
nation (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).
DESCRIPTIONMPI_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 destina‐
tion 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 com‐
bination 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 inde‐
gree and outdegree as zero and thus do not occur as source or destina‐
tion 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 influ‐
ence the process remapping strategy and other internal MPI optimiza‐
tions. For instance, approximate count arguments of later communication
calls along specic edges could be used as their edge weights. Multi‐
plicity 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 outde‐
gree 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 For‐
tran, 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_neigh‐
bors_count
1.7.4 Feb 04, 2014MPI_Dist_graph_create_adjacent(3)
