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mpi_graph_neighbors(3openmpi) [osx man page]

MPI_Graph_neighbors(3OpenMPI)											     MPI_Graph_neighbors(3OpenMPI)

NAME
MPI_Graph_neighbors - Returns the neighbors of a node associated with a graph topology. SYNTAX
C Syntax #include <mpi.h> int MPI_Graph_neighbors(MPI_Comm comm, int rank, int maxneighbors, int *neighbors) Fortran Syntax INCLUDE 'mpif.h' MPI_GRAPH_NEIGHBORS(COMM, RANK, MAXNEIGHBORS, NEIGHBORS, IERROR) INTEGER COMM, RANK, MAXNEIGHBORS, NEIGHBORS(*), IERROR C++ Syntax #include <mpi.h> void Graphcomm::Get_neighbors(int rank, int maxneighbors, int neighbors[]) const INPUT PARAMETERS
comm Communicator with graph topology (handle). rank Rank of process in group of comm (integer). maxneighbors Size of array neighbors (integer). OUTPUT PARAMETERS
neighbors Ranks of processes that are neighbors to specified process (array of integers). IERROR Fortran only: Error status (integer). DESCRIPTION
Example: Suppose that comm is a communicator with a shuffle-exchange topology. The group has 2n members. Each process is labeled by a(1), ..., a(n) with a(i) E{0,1}, and has three neighbors: exchange (a(1), ..., a(n) = a(1), ..., a(n-1), a(n) (a = 1 - a), shuffle (a(1), ..., a(n)) = a(2), ..., a(n), a(1), and unshuffle (a(1), ..., a(n)) = a(n), a(1), ..., a(n-1). The graph adjacency list is illus- trated below for n=3. exchange shuffle unshuffle node neighbors(1) neighbors(2) neighbors(3) 0(000) 1 0 0 1(001) 0 2 4 2(010) 3 4 1 3(011) 2 6 5 4(100) 5 1 2 5(101) 4 3 6 6(110) 7 5 3 7(111) 6 7 7 Suppose that the communicator comm has this topology associated with it. The following code fragment cycles through the three types of neighbors and performs an appropriate permutation for each. C assume: each process has stored a real number A. C extract neighborhood information CALL MPI_COMM_RANK(comm, myrank, ierr) CALL MPI_GRAPH_NEIGHBORS(comm, myrank, 3, neighbors, ierr) C perform exchange permutation CALL MPI_SENDRECV_REPLACE(A, 1, MPI_REAL, neighbors(1), 0, + neighbors(1), 0, comm, status, ierr) C perform shuffle permutation CALL MPI_SENDRECV_REPLACE(A, 1, MPI_REAL, neighbors(2), 0, + neighbors(3), 0, comm, status, ierr) C perform unshuffle permutation CALL MPI_SENDRECV_REPLACE(A, 1, MPI_REAL, neighbors(3), 0, + neighbors(2), 0, comm, status, ierr) ERRORS
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ func- tions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI:Exception object. 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_Graph_neighbors_count Open MPI 1.2 September 2006 MPI_Graph_neighbors(3OpenMPI)

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MPI_Cart_coords(3OpenMPI)												 MPI_Cart_coords(3OpenMPI)

NAME
MPI_Cart_coords - Determines process coords in Cartesian topology given rank in group. SYNTAX
C Syntax #include <mpi.h> int MPI_Cart_coords(MPI_Comm comm, int rank, int maxdims, int *coords) Fortran Syntax INCLUDE 'mpif.h' MPI_CART_COORDS(COMM, RANK, MAXDIMS, COORDS, IERROR) INTEGER COMM, RANK, MAXDIMS, COORDS(*), IERROR C++ Syntax #include <mpi.h> void Cartcomm::Get_coords(int rank, int maxdims, int coords[]) const INPUT PARAMETERS
comm Communicator with Cartesian structure (handle). rank Rank of a process within group of comm (integer). maxdims Length of vector coord in the calling program (integer). OUTPUT PARAMETERS
coords Integer array (of size ndims,which was defined by MPI_Cart_create call) containing the Cartesian coordinates of specified process (integer). IERROR Fortran only: Error status (integer). DESCRIPTION
The inverse mapping, rank-to-coordinates translation is provided by MPI_Cart_coords. ERRORS
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ func- tions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI:Exception object. 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. Open MPI 1.2 September 2006 MPI_Cart_coords(3OpenMPI)
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