.TH MPI_Neighbor_alltoallw 3 "11/12/2019" " " "MPI"
.SH NAME
MPI_Neighbor_alltoallw \-  Like MPI_Neighbor_alltoallv but it allows one to send and receive with different types to and from each neighbor. 
.SH SYNOPSIS
.nf
int MPI_Neighbor_alltoallw(const void *sendbuf, const int sendcounts[], const MPI_Aint sdispls[],
const MPI_Datatype sendtypes[], void *recvbuf, const int recvcounts[],
const MPI_Aint rdispls[], const MPI_Datatype recvtypes[], MPI_Comm comm)
.fi
.SH INPUT PARAMETERS
.PD 0
.TP
.B sendbuf 
- starting address of the send buffer (choice)
.PD 1
.PD 0
.TP
.B sendcounts 
- non-negative integer array (of length outdegree) specifying the number of elements to send to each neighbor
.PD 1
.PD 0
.TP
.B sdispls 
- integer array (of length outdegree).  Entry j specifies the displacement in bytes (relative to sendbuf) from which to take the outgoing data destined for neighbor j (array of integers)
.PD 1
.PD 0
.TP
.B sendtypes 
- array of datatypes (of length outdegree).  Entry j specifies the type of data to send to neighbor j (array of handles)
.PD 1
.PD 0
.TP
.B recvcounts 
- non-negative integer array (of length indegree) specifying the number of elements that are received from each neighbor
.PD 1
.PD 0
.TP
.B rdispls 
- integer array (of length indegree).  Entry i specifies the displacement in bytes (relative to recvbuf) at which to place the incoming data from neighbor i (array of integers).
.PD 1
.PD 0
.TP
.B recvtypes 
- array of datatypes (of length indegree).  Entry i specifies the type of data received from neighbor i (array of handles).
.PD 1
.PD 0
.TP
.B comm 
- communicator with topology structure (handle)
.PD 1

.SH OUTPUT PARAMETERS
.PD 0
.TP
.B recvbuf 
- starting address of the receive buffer (choice)
.PD 1

.SH 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 
.I malloc
or other non-MPICH runtime routines that are themselves not interrupt-safe.

.SH NOTES FOR FORTRAN
All MPI routines in Fortran (except for 
.I MPI_WTIME
and 
.I MPI_WTICK
) have
an additional argument 
.I ierr
at the end of the argument list.  
.I 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
.I call
statement.

All MPI objects (e.g., 
.I MPI_Datatype
, 
.I MPI_Comm
) are of type 
.I INTEGER
in Fortran.

.SH ERRORS

All MPI routines (except 
.I MPI_Wtime
and 
.I 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 
.I MPI_Comm_set_errhandler
(for communicators),
.I MPI_File_set_errhandler
(for files), and 
.I MPI_Win_set_errhandler
(for
RMA windows).  The MPI-1 routine 
.I MPI_Errhandler_set
may be used but
its use is deprecated.  The predefined error handler
.I MPI_ERRORS_RETURN
may be used to cause error values to be returned.
Note that MPI does 
.B not
guarentee that an MPI program can continue past
an error; however, MPI implementations will attempt to continue whenever
possible.