MPI_Iscan(3) MPI MPI_Iscan(3)
NAME
MPI_Iscan - Computes the scan (partial reductions) of data on a
collection of processes in a nonblocking way
SYNOPSIS
int MPI_Iscan(const void *sendbuf, void *recvbuf, int count,
MPI_Datatype datatype, MPI_Op op, MPI_Comm comm,
MPI_Request *request)
int MPI_Iscan_c(const void *sendbuf, void *recvbuf, MPI_Count count,
MPI_Datatype datatype, MPI_Op op, MPI_Comm comm,
MPI_Request *request)
INPUT PARAMETERS
sendbuf
- starting address of send buffer (choice)
count - number of elements in input buffer (non-negative 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)
request
- communication request (handle)
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.
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
guarantee 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_ARG
- Invalid argument. Some argument is invalid and is not
identified by a specific error class (e.g., MPI_ERR_RANK ).
MPI_ERR_BUFFER
- Invalid buffer pointer. Usually a null buffer where one is not
valid.
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_OP
- Invalid operation. MPI operations (objects of type MPI_Op )
must either be one of the predefined operations (e.g., MPI_SUM )
or created with MPI_Op_create .
MPI_ERR_TYPE
- Invalid datatype argument. Additionally, this error can occur
if an uncommitted MPI_Datatype (see MPI_Type_commit ) is used in a
communication call.
MPI_ERR_OTHER
- Other error; use MPI_Error_string to get more information about
this error code.
1/27/2023 MPI_Iscan(3)
mpi 4.1 - Generated Sat Jan 28 18:33:32 CST 2023