MPI_Gather(3)			      MPI			 MPI_Gather(3)

NAME
       MPI_Gather -  Gathers together values from a group of processes

SYNOPSIS
       int MPI_Gather(const void *sendbuf, int sendcount, MPI_Datatype sendtype,
		      void *recvbuf, int recvcount, MPI_Datatype recvtype,
		      int root, 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)
       recvcount
	      -	 number	 of elements for any single receive (integer, signifi‐
	      cant only at root)
       recvtype
	      - data type of recv buffer elements (significant only  at	 root)
	      (handle)
       root   - rank of receiving process (integer)
       comm   - communicator (handle)

OUTPUT PARAMETERS
       recvbuf
	      - address of receive buffer (choice, significant only at root )

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.

       MPI_SUCCESS
	      - No error; MPI routine completed successfully.
       MPI_ERR_COMM
	      - Invalid communicator.  A common error is to use a null	commu‐
	      nicator in a call (not even allowed in MPI_Comm_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 ).
       MPI_ERR_BUFFER
	      -	 Invalid  buffer  pointer.  Usually a null buffer where one is
	      not valid.

LOCATION
       src/mpi/coll/gather.c

				   8/22/2013			 MPI_Gather(3)

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