Synopsis

int MPI_Win_get_attr(MPI_Win win, int win_keyval, void *attribute_val,
                     int *flag)

Input Parameters

win

window to which the attribute is attached (handle)

win_keyval

key value (integer)

Output Parameters

attribute_val

attribute value, unless flag = false (None)

flag

false if no attribute is associated with the key (logical)

Notes

The following attributes are predefined for all MPI Window objects:

  • MPI_WIN_BASE - window base address.

  • MPI_WIN_SIZE - window size, in bytes.

  • MPI_WIN_DISP_UNIT - displacement unit associated with the window.

Attributes must be extracted from the same language as they were inserted in with MPI_ATTR_PUT. The notes for C and Fortran below explain why.

Notes for C

Even though the attribute_val argument is declared as void **, it is really the address of a void pointer (i.e., a void ***). Using a void *, however, is more in keeping with C idiom and allows the pointer to be passed without additional casts.

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. The attribute_val in Fortran is a pointer to a Fortran integer, not a pointer to a void *.

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_KEYVAL - Invalid keyval

  • MPI_ERR_WIN - Invalid MPI window object

  • MPI_ERR_OTHER - Other error; use 'MPI_Error_string' to get more information about this error code.