# MPI_Win_create_keyval

## NAME

MPI_Win_create_keyval − Creates a keyval for a window.

## SYNTAX

## C Syntax

#include <mpi.h>
int MPI_Win_create_keyval(MPI_Win_copy_attr_function *win_copy_attr_fn,

|  | MPI_Win_delete_attr_function *win_delete_attr_fn,
|  | int *win_keyval, void *extra_state)

## Fortran Syntax (see FORTRAN 77 NOTES)

INCLUDE ’mpif.h’
MPI_WIN_CREATE_KEYVAL(WIN_COPY_ATTR_FN, WIN_DELETE_ATTR_FN,

| WIN_KEYVAL, EXTRA_STATE, IERROR)
| EXTERNAL WIN_COPY_ATTR_FN, WIN_DELETE_ATTR_FN
| INTEGER WIN_KEYVAL, IERROR
| INTEGER(KIND=MPI_ADDRESS_KIND) EXTRA_STATE

## C++ Syntax

#include <mpi.h>
static int MPI::Win::Create_keyval(MPI::Win::Copy_attr_function*

| win_copy_attr_fn,
| MPI::Win::Delete_attr_function* win_delete_attr_fn,
| void* extra_state)

## INPUT PARAMETERS

win_copy_attr_fn

Copy callback function for win_keyval (function).

win_delete_attr_fn

Delete callback function for win_keyval (function).

extra_state

Extra state for callback functions.

## OUTPUT PARAMETERS

win_keyval

Key value for future access (integer).

| IERROR |  | Fortran only: Error status (integer). |

## DESCRIPTION

The argument win_copy_attr_fn may be specified as MPI_WIN_NULL_COPY_FN or MPI_WIN_DUP_FN from either C, C++, or Fortran. MPI_WIN_NULL_COPY_FN is a function that serves only to return flag = 0 and MPI_SUCCESS. MPI_WIN_DUP_FN is a simple-minded copy function that sets flag = 1, returns the value of attribute_val_in in attribute_val_out, and returns MPI_SUCCESS.

The argument win_delete_attr_fn may be specified as MPI_WIN_NULL_DELETE_FN from either C, C++, or Fortran. MPI_WIN_NULL_DELETE_FN is a function that serves only to return MPI_SUCCESS.

The C callback functions are:

typedef int MPI_Win_copy_attr_function(MPI_Win oldwin, int win_keyval,
void *extra_state, void *attribute_val_in,
void *attribute_val_out, int *flag);

and

typedef int MPI_Win_delete_attr_function(MPI_Win win, int win_keyval,
void *attribute_val, void *extra_state);

The Fortran callback functions are:

SUBROUTINE WIN_COPY_ATTR_FN(OLDWIN, WIN_KEYVAL, EXTRA_STATE,

|  | ATTRIBUTE_VAL_IN, ATTRIBUTE_VAL_OUT, FLAG, IERROR) |
|  | INTEGER OLDWIN, WIN_KEYVAL, IERROR |
|  | INTEGER(KIND=MPI_ADDRESS_KIND) EXTRA_STATE, ATTRIBUTE_VAL_IN, |
|  |  | ATTRIBUTE_VAL_OUT
|  | LOGICAL FLAG |

and

SUBROUTINE WIN_DELETE_ATTR_FN(WIN, WIN_KEYVAL, ATTRIBUTE_VAL,

| EXTRA_STATE, IERROR)
| INTEGER WIN, WIN_KEYVAL, IERROR
| INTEGER(KIND=MPI_ADDRESS_KIND) ATTRIBUTE_VAL, EXTRA_STATE

The C++ callbacks are:

typedef int MPI::Win::Copy_attr_function(const MPI::Win& oldwin,

| int win_keyval, void* extra_state, void* attribute_val_in,
| void* attribute_val_out, bool& flag);

and

typedef int MPI::Win::Delete_attr_function(MPI::Win& win, int win_keyval, void* attribute_val, void* extra_state);

## FORTRAN 77 NOTES

The MPI standard prescribes portable Fortran syntax for the EXTRA_STATE argument only for Fortran 90. FORTRAN 77 users may use the non-portable syntax

INTEGER*MPI_ADDRESS_KIND EXTRA_STATE

where MPI_ADDRESS_KIND is a constant defined in mpif.h and gives the length of the declared integer in bytes.

## ERRORS

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism will be used to throw an MPI:Exception object.

Before the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; 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.

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