MPI_Alltoallw(3)							MPI							  MPI_Alltoallw(3)

NAME

       MPI_Alltoallw -	Generalized all-to-all communication allowing different datatypes, counts, and displacements for each partner

SYNOPSIS

       int MPI_Alltoallw(void *sendbuf, int *sendcnts, int *sdispls,
			 MPI_Datatype *sendtypes, void *recvbuf, int *recvcnts,
			 int *rdispls, MPI_Datatype *recvtypes, MPI_Comm comm)

INPUT PARAMETERS

       sendbuf
	      - starting address of send buffer (choice)
       sendcounts
	      - integer array equal to the group size specifying the number of elements to send to each processor (integer)
       sdispls
	      -  integer  array  (of  length group size). Entry j specifies the displacement in bytes (relative to sendbuf) from which to take the
	      outgoing data destined for process j
       sendtypes
	      - array of datatypes (of length group size). Entry j specifies the type of data to send to process j (handle)
       recvcounts
	      - integer array equal to the group size specifying the number of elements that can be received from each processor (integer)
       rdispls
	      - integer array (of length group size). Entry i specifies the displacement in bytes (relative to recvbuf)  at  which  to	place  the
	      incoming data from process i
       recvtypes
	      - array of datatypes (of length group size). Entry i specifies the type of data received from process i (handle)
       comm   - communicator (handle)

OUTPUT PARAMETER

       recvbuf
	      - address of 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  communicators), 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	predefined
       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.

       MPI_SUCCESS
	      - No error; MPI routine completed successfully.
       MPI_ERR_COMM
	      - Invalid communicator.  A common error is to use a null communicator in a call (not even allowed in MPI_Comm_rank ).
       MPI_ERR_ARG
	      - Invalid argument.  Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK ).
       MPI_ERR_COUNT
	      - Invalid count argument.  Count arguments must be non-negative; a count of zero is often valid.
       MPI_ERR_TYPE
	      - Invalid datatype argument.  May be an uncommitted MPI_Datatype (see MPI_Type_commit ).

LOCATION

       alltoallw.c

								     1/21/2011							  MPI_Alltoallw(3)