NAME¶
MPI_Scan - Computes the scan (partial reductions) of data on a collection of
processes
SYNOPSIS¶
int MPI_Scan(const void *sendbuf, void *recvbuf, int count, MPI_Datatype datatype,
MPI_Op op, MPI_Comm comm)
- sendbuf
- - starting address of send buffer (choice)
- count
- - number of elements in input buffer (integer)
- datatype
- - data type of elements of input buffer (handle)
- op
- - operation (handle)
- comm
- - communicator (handle)
OUTPUT PARAMETERS¶
- recvbuf
- - starting 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.
NOTES ON COLLECTIVE OPERATIONS¶
The reduction functions (
MPI_Op ) do not return an error value. As a
result, if the functions detect an error, all they can do is either call
MPI_Abort or silently skip the problem. Thus, if you change the error
handler from
MPI_ERRORS_ARE_FATAL to something else, for example,
MPI_ERRORS_RETURN , then no error may be indicated.
The reason for this is the performance problems in ensuring that all collective
routines return the same error value.
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_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.
- MPI_ERR_BUFFER
- - This error class is associcated with an error code that indicates that
two buffer arguments are aliased ; that is, the describe
overlapping storage (often the exact same storage). This is prohibited in
MPI (because it is prohibited by the Fortran standard, and rather than
have a separate case for C and Fortran, the MPI Forum adopted the more
restrictive requirements of Fortran).
LOCATION¶
/tmp/gyCYfBi4J6/mpich-3.1/src/mpi/coll/scan.c