MPI_Allgatherv(3)							MPI							 MPI_Allgatherv(3)

NAME

       MPI_Allgatherv -  Gathers data from all tasks and deliver the combined data to all tasks

SYNOPSIS

       int MPI_Allgatherv(void *sendbuf, int sendcount, MPI_Datatype sendtype,
			  void *recvbuf, int *recvcounts, int *displs,
			  MPI_Datatype recvtype, MPI_Comm comm)

INPUT PARAMETERS

       sendbuf
	      - starting address of send buffer (choice)
       sendcount
	      - number of elements in send buffer (integer)
       sendtype
	      - data type of send buffer elements (handle)
       recvcounts
	      - integer array (of length group size) containing the number of elements that are to be received from each process
       displs -  integer  array  (of  length group size). Entry i specifies the displacement (relative to recvbuf ) at which to place the incoming
	      data from process i

       recvtype
	      - data type of receive buffer elements (handle)
       comm   - communicator (handle)

OUTPUT PARAMETER

       recvbuf
	      - address of receive buffer (choice)

NOTES

       The MPI standard (1.0 and 1.1) says that

       The jth block of data sent from each process is received by every process and placed in the jth block of the buffer recvbuf .

       This is misleading; a better description is

       The block of data sent from the jth process is received by every process and placed in the jth block of the buffer recvbuf .

       This text was suggested by Rajeev Thakur, and has been adopted as a clarification to the MPI standard by the MPI-Forum.

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_ERR_BUFFER
	      - Invalid buffer pointer.  Usually a null buffer where one is not valid.
       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

       allgatherv.c

								     1/21/2011							 MPI_Allgatherv(3)