17.2.259. MPI_Neighbor_allgather_init
MPI_Neighbor_allgather, MPI_Ineighbor_allgather, MPI_Neighbor_allgather — Gathers and distributes data from and to all neighbors
17.2.259.1. SYNTAX
17.2.259.1.1. C Syntax
#include <mpi.h>
int MPI_Neighbor_allgather(const void *sendbuf, int sendcount,
MPI_Datatype sendtype, void *recvbuf, int recvcount,
MPI_Datatype recvtype, MPI_Comm comm)
int MPI_Ineighbor_allgather(const void *sendbuf, int sendcount,
MPI_Datatype sendtype, void *recvbuf, int recvcount,
MPI_Datatype recvtype, MPI_Comm comm, MPI_Request req)
int MPI_Neighbor_allgather_init(const void *sendbuf, int sendcount,
MPI_Datatype sendtype, void *recvbuf, int recvcount,
MPI_Datatype recvtype, MPI_Comm comm, MPI_Infoinfo, MPI_Request req)
17.2.259.1.2. Fortran Syntax
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_NEIGHBOR_ALLGATHER(SENDBUF, SENDCOUNT, SENDTYPE, RECVBUF, RECVCOUNT,
RECVTYPE, COMM, IERROR)
<type> SENDBUF (*), RECVBUF (*)
INTEGER SENDCOUNT, SENDTYPE, RECVCOUNT, RECVTYPE, COMM,
INTEGER IERROR
MPI_INEIGHBOR_ALLGATHER(SENDBUF, SENDCOUNT, SENDTYPE, RECVBUF, RECVCOUNT,
RECVTYPE, COMM, REQUEST, IERROR)
<type> SENDBUF (*), RECVBUF (*)
INTEGER SENDCOUNT, SENDTYPE, RECVCOUNT, RECVTYPE, COMM,
INTEGER REQUEST, IERROR
MPI_NEIGHBOR_ALLGATHER_INIT(SENDBUF, SENDCOUNT, SENDTYPE, RECVBUF, RECVCOUNT,
RECVTYPE, COMM, INFO, IREQUEST, IERROR)
<type> SENDBUF (*), RECVBUF (*)
INTEGER SENDCOUNT, SENDTYPE, RECVCOUNT, RECVTYPE, COMM,
INTEGER INFO, REQUEST, IERROR
17.2.259.1.3. Fortran 2008 Syntax
USE mpi_f08
MPI_Neighbor_allgather(sendbuf, sendcount, sendtype, recvbuf, recvcount,
recvtype, comm, ierror)
TYPE(*), DIMENSION(..), INTENT(IN) :: sendbuf
TYPE(*), DIMENSION(..) :: recvbuf
INTEGER, INTENT(IN) :: sendcount, recvcount
TYPE(MPI_Datatype), INTENT(IN) :: sendtype, recvtype
TYPE(MPI_Comm), INTENT(IN) :: comm
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_Ineighbor_allgather(sendbuf, sendcount, sendtype, recvbuf, recvcount,
recvtype, comm, request, ierror)
TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: sendbuf
TYPE(*), DIMENSION(..), ASYNCHRONOUS :: recvbuf
INTEGER, INTENT(IN) :: sendcount, recvcount
TYPE(MPI_Datatype), INTENT(IN) :: sendtype, recvtype
TYPE(MPI_Comm), INTENT(IN) :: comm
TYPE(MPI_Request), INTENT(OUT) :: request
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
MPI_Neighbor_allgather_init(sendbuf, sendcount, sendtype, recvbuf, recvcount,
recvtype, comm, info, request, ierror)
TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: sendbuf
TYPE(*), DIMENSION(..), ASYNCHRONOUS :: recvbuf
INTEGER, INTENT(IN) :: sendcount, recvcount
TYPE(MPI_Datatype), INTENT(IN) :: sendtype, recvtype
TYPE(MPI_Comm), INTENT(IN) :: comm
TYPE(MPI_Info), INTENT(IN) :: info
TYPE(MPI_Request), INTENT(OUT) :: request
INTEGER, OPTIONAL, INTENT(OUT) :: ierror
17.2.259.2. INPUT PARAMETERS
sendbuf
: Starting address of send buffer (choice).sendcount
: Number of elements in send buffer (integer).sendtype
: Datatype of send buffer elements (handle).recvbuf
: Starting address of recv buffer (choice).recvcount
: Number of elements received from any process (integer).recvtype
: Datatype of receive buffer elements (handle).comm
: Communicator (handle).
17.2.259.3. OUTPUT PARAMETERS
recvbuf
: Address of receive buffer (choice).request
: Request (handle, non-blocking and persistent only).ierror
: Fortran only: Error status (integer).
17.2.259.4. DESCRIPTION
MPI_Neighbor_allgather is similar to MPI_Allgather, except that only the neighboring processes receive the result, instead of all processes. The neighbors and buffer layout is determined by the topology of comm.
The type signature associated with sendcount, sendtype at a process must be equal to the type signature associated with recvcount, recvtype at any other process.
17.2.259.5. NEIGHBOR ORDERING
For a distributed graph topology, created with MPI_Dist_graph_create, the sequence of neighbors in the send and receive buffers at each process is defined as the sequence returned by MPI_Dist_graph_neighbors for destinations and sources, respectively. For a general graph topology, created with MPI_Graph_create, the order of neighbors in the send and receive buffers is defined as the sequence of neighbors as returned by MPI_Graph_neighbors. Note that general graph topologies should generally be replaced by the distributed graph topologies.
For a Cartesian topology, created with MPI_Cart_create, the sequence of
neighbors in the send and receive buffers at each process is defined by
order of the dimensions, first the neighbor in the negative direction
and then in the positive direction with displacement 1. The numbers of
sources and destinations in the communication routines are 2*ndims with
ndims defined in MPI_Cart_create. If a neighbor does not exist, i.e., at
the border of a Cartesian topology in the case of a non-periodic virtual
grid dimension (i.e., periods[…]==false), then this neighbor is
defined to be MPI_PROC_NULL
.
If a neighbor in any of the functions is MPI_PROC_NULL
, then the
neighborhood collective communication behaves like a point-to-point
communication with MPI_PROC_NULL
in this direction. That is, the buffer
is still part of the sequence of neighbors but it is neither
communicated nor updated.
17.2.259.6. NOTES
The MPI_IN_PLACE option for sendbuf is not meaningful for this operation.
17.2.259.7. ERRORS
Almost all MPI routines return an error value; C routines as the return result of the function and Fortran routines in the last argument.
Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions.
Open MPI includes three predefined error handlers that can be used:
MPI_ERRORS_ARE_FATAL
Causes the program to abort all connected MPI processes.MPI_ERRORS_ABORT
An error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI_Abort was called on that communicator. If called on a window or file, acts as if MPI_Abort was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process.MPI_ERRORS_RETURN
Returns an error code to the application.
MPI applications can also implement their own error handlers by calling:
Note that MPI does not guarantee that an MPI program can continue past an error.
See the MPI man page for a full list of MPI error codes.
See the Error Handling section of the MPI-3.1 standard for more information.
See also
MPI_Garph_create