MPI_Neighbor_alltoall(3) MPI MPI_Neighbor_alltoall(3)NAMEMPI_Neighbor_alltoall - In this function, each process i receives data
items from each process j if an edge (j,i) exists in the topology graph
or Cartesian topology. Similarly, each process i sends data items to
all processes j where an edge (i,j) exists. This call is more general
than MPI_NEIGHBOR_ALLGATHER in that different data items can be sent to
each neighbor. The k-th block in send buffer is sent to the k-th neigh‐
boring process and the l-th block in the receive buffer is received
from the l-th neighbor.
SYNOPSIS
int MPI_Neighbor_alltoall(const void *sendbuf, int sendcount, MPI_Datatype sendtype, void *recvbuf, int recvcount, MPI_Datatype recvtype, MPI_Comm comm)
INPUT PARAMETERS
sendbuf
- starting address of the send buffer (choice)
sendcount
- number of elements sent to each neighbor (non-negative inte‐
ger)
sendtype
- data type of send buffer elements (handle)
recvcount
- number of elements received from each neighbor (non-negative
integer)
recvtype
- data type of receive buffer elements (handle)
comm - communicator (handle)
OUTPUT PARAMETERS
recvbuf
- starting address of the receive buffer (choice)
THREAD AND INTERRUPT SAFETY
This routine is thread-safe. This means that this routine may be
safely used by multiple threads without the need for any user-provided
thread locks. However, the routine is not interrupt safe. Typically,
this is due to the use of memory allocation routines such as malloc or
other non-MPICH runtime routines that are themselves not interrupt-
safe.
NOTES FOR FORTRAN
All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have
an additional argument ierr at the end of the argument list. ierr is
an integer and has the same meaning as the return value of the routine
in C. In Fortran, MPI routines are subroutines, and are invoked with
the call statement.
All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in
Fortran.
ERRORS
All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error
value; C routines as the value of the function and Fortran routines in
the last argument. Before the value is returned, the current MPI error
handler is called. By default, this error handler aborts the MPI job.
The error handler may be changed with MPI_Comm_set_errhandler (for com‐
municators), MPI_File_set_errhandler (for files), and
MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine
MPI_Errhandler_set may be used but its use is deprecated. The prede‐
fined error handler MPI_ERRORS_RETURN may be used to cause error values
to be returned. Note that MPI does not guarentee that an MPI program
can continue past an error; however, MPI implementations will attempt
to continue whenever possible.
11/9/2015 MPI_Neighbor_alltoall(3)
