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MPI_Neighbor_allgatherv, MPI_Ineighbor_allgatherv - Gathers and
distributes data from and to all neighbors. Each process may contribute
a different amount of data.
#include <mpi.h>
int MPI_Neighbor_allgatherv(const void *sendbuf, int sendcount,
MPI_Datatype sendtype, void *recvbuf, const int recvcounts[],
const int displs[], MPI_Datatype recvtype, MPI_Comm comm)
int MPI_Ineighbor_allgatherv(const void *sendbuf, int sendcount,
MPI_Datatype sendtype, void *recvbuf, const int recvcounts[],
const int displs[], MPI_Datatype recvtype, MPI_Comm comm,
MPI_Request *request)
INCLUDE ’mpif.h’
MPI_NEIGHBOR_ALLGATHERV(SENDBUF, SENDCOUNT, SENDTYPE, RECVBUF,
RECVCOUNT, DISPLS, RECVTYPE, COMM, IERROR)
<type> SENDBUF(*), RECVBUF(*)
INTEGER SENDCOUNT, SENDTYPE, RECVCOUNT(*),
INTEGER DISPLS(*), RECVTYPE, COMM, IERROR
MPI_INEIGHBOR_ALLGATHERV(SENDBUF, SENDCOUNT, SENDTYPE, RECVBUF,
RECVCOUNT, DISPLS, RECVTYPE, COMM, REQUEST, IERROR)
<type> SENDBUF(*), RECVBUF(*)
INTEGER SENDCOUNT, SENDTYPE, RECVCOUNT(*),
INTEGER DISPLS(*), RECVTYPE, COMM,REQUEST, IERROR
- sendbuf
- Starting address of send buffer (choice).
- sendcount
- Number of elements in send buffer (integer).
- sendtype
- Datatype of send buffer
elements (handle).
- recvcount
- Integer array (of length group size) containing
the number of elements that are received from each neighbor.
- displs
- Integer
array (of length group size). Entry i specifies the displacement (relative
to recvbuf) at which to place the incoming data from neighbor i.
- recvtype
- Datatype of receive buffer elements (handle).
- comm
- Communicator (handle).
- recvbuf
- Address of receive buffer (choice).
- request
- Request
(handle, non-blocking only).
- IERROR
- Fortran only: Error status (integer).
MPI_Neighbor_allgatherv is similar to MPI_Neighbor_allgather
in that all processes gather data from all neighbors, except that each
process can send a different amount of data. The block of data sent from
the jth neighbor is received by every neighbor and placed in the jth block
of the buffer. The neighbors and buffer layout is determined by the topology
of comm. recvbuf.
The type signature associated with sendcount, sendtype,
at process j must be equal to the type signature associated with the corresponding
entry in recvcounts on neighboring processes.
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.
The
MPI_IN_PLACE option for sendbuf is not meaningful for this operation.
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.
MPI_Neighbor_allgather MPI_Cart_create MPI_Graph_create MPI_Dist_graph_create
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