mpi_allgather(3) [debian man page]

MPI_Allgather(3)							MPI							  MPI_Allgather(3)

NAME

       MPI_Allgather -	Gathers data from all tasks and distribute the combined data to all tasks

SYNOPSIS

       int MPI_Allgather(void *sendbuf, int sendcount, MPI_Datatype sendtype,
			 void *recvbuf, int recvcount, 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)
       recvcount
	      - number of elements received from any process (integer)
       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 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_COMM
	      - Invalid communicator.  A common error is to use a null communicator 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

       allgather.c

								     1/21/2011							  MPI_Allgather(3)