MPI_Win_create(3) MPI MPI_Win_create(3)NAMEMPI_Win_create - Create an MPI Window object for one-sided communica‐
tion
SYNOPSIS
int MPI_Win_create(void *base, MPI_Aint size, int disp_unit, MPI_Info info,
MPI_Comm comm, MPI_Win *win)
This is a collective call executed by all processes in the group of
comm. It returns a window object that can be used by these processes to
perform RMA operations. Each process specifies a window of existing
memory that it exposes to RMA accesses by the processes in the group of
comm. The window consists of size bytes, starting at address base. In
C, base is the starting address of a memory region. In Fortran, one can
pass the first element of a memory region or a whole array, which must
be 'simply contiguous' (for 'simply contiguous', see also MPI 3.0, Sec‐
tion 17.1.12 on page 626). A process may elect to expose no memory by
specifying size = 0.
INPUT PARAMETERS
base - initial address of window (choice)
size - size of window in bytes (nonnegative integer)
disp_unit
- local unit size for displacements, in bytes (positive integer)
info - info argument (handle)
comm - communicator (handle)
OUTPUT PARAMETERS
win - window object returned by the call (handle)
NOTES
The displacement unit argument is provided to facilitate address arith‐
metic in RMA operations: the target displacement argument of an RMA
operation is scaled by the factor disp_unit specified by the target
process, at window creation.
The info argument provides optimization hints to the runtime about the
expected usage pattern of the window. The following info keys are pre‐
defined.
no_locks
- If set to true, then the implementation may assume that pas‐
sive target synchronization (i.e., MPI_Win_lock ,
MPI_Win_lock_all ) will not be used on the given window. This
implies that this window is not used for 3-party communication,
and RMA can be implemented with no (less) asynchronous agent
activity at this process.
accumulate_ordering
- Controls the ordering of accumulate operations at the target.
The argument string should contain a comma-separated list of the
following read/write ordering rules, where e.g. "raw" means
read-after-write: "rar,raw,war,waw".
accumulate_ops
- If set to same_op, the implementation will assume that all
concurrent accumulate calls to the same target address will use
the same operation. If set to same_op_no_op, then the implemen‐
tation will assume that all concurrent accumulate calls to the
same target address will use the same operation or MPI_NO_OP .
This can eliminate the need to protect access for certain opera‐
tion types where the hardware can guarantee atomicity. The
default is same_op_no_op.
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_ARG
- Invalid argument. Some argument is invalid and is not identi‐
fied by a specific error class (e.g., MPI_ERR_RANK ).
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_INFO
- Invalid Info
MPI_ERR_OTHER
- Other error; use MPI_Error_string to get more information
about this error code.
MPI_ERR_SIZE
-
SEE ALSO
MPI_Win_allocate MPI_Win_allocate_shared MPI_Win_create_dynamic
MPI_Win_free
LOCATION
src/mpi/rma/win_create.c
8/22/2013 MPI_Win_create(3)
