#include <mpi.h> int MPI_Graph_create(MPI_Comm comm_old, int nnodes, int *index, int *edges, int reorder, MPI_Comm *comm_graph)
INCLUDE 'mpif.h' MPI_GRAPH_CREATE(COMM_OLD, NNODES, INDEX, EDGES, REORDER, COMM_GRAPH, IERROR) INTEGER COMM_OLD, NNODES, INDEX(*), EDGES(*) INTEGER COMM_GRAPH, IERROR LOGICAL REORDER
#include <mpi.h> Graphcomm Intracomm::Create_graph(int nnodes, const int index[], const int edges[], bool reorder) const
The three parameters nnodes, index, and edges define the graph structure. nnodes is the number of nodes of the graph. The nodes are numbered from 0 to nnodes-1. The ith entry of array index stores the total number of neighbors of the first i graph nodes. The lists of neighbors of nodes 0, 1, ..., nnodes-1 are stored in consecutive locations in array edges. The array edges is a flattened representation of the edge lists. The total number of entries in index is nnodes and the total number of entries in edges is equal to the number of graph edges.
The definitions of the arguments nnodes, index, and edges are illustrated with the following simple example.
Example: Assume there are four processes 0, 1, 2, 3 with the following adjacency matrix:
Process Neighbors 0 1, 3 1 0 2 3 3 0, 2
Then, the input arguments are:
nnodes = 4 index = 2, 3, 4, 6 edges = 1, 3, 0, 3, 0, 2
Thus, in C, index[0] is the degree of node zero, and index[i] - index[i-1] is the degree of node i, i=1, . . . , nnodes-1; the list of neighbors of node zero is stored in edges[j], for 0 <= j <= index[0] - 1 and the list of neighbors of node i, i > 0 , is stored in edges[j], index[i-1] <= j <= index[i] - 1.
In Fortran, index(1) is the degree of node zero, and index(i+1) - index(i) is the degree of node i, i=1, . . . , nnodes-1; the list of neighbors of node zero is stored in edges(j), for 1 <= j <= index(1) and the list of neighbors of node i, i > 0, is stored in edges(j), index(i) + 1 <= j <= index(i + 1).
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_Graph_get
MPI_Graphdims_get