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MPI_Attr_get(3) MPI MPI_Attr_get(3)
MPI_Attr_get - Retrieves attribute value by key
int MPI_Attr_get(MPI_Comm comm, int keyval, void *attr_value, int *flag)
comm - communicator to which attribute is attached (handle)
keyval - key value (integer)
- attribute value, unless flag = false
flag - true if an attribute value was extracted; false if no
attribute is associated with the key
Attributes must be extracted from the same language as they were
inserted in with MPI_ATTR_PUT . The notes for C and Fortran below
NOTES FOR C
Even though the attr_value arguement 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-
The MPI-2 standard deprecated a number of routines because MPI-2
provides better versions. This routine is one of those that was
deprecated. The routine may continue to be used, but new code should
use the replacement routine. The replacement for this routine is
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
The attr_value in Fortran is a pointer to a Fortran integer, not a
pointer to a void * .
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.
- No error; MPI routine completed successfully.
- Invalid communicator. A common error is to use a null
communicator in a call (not even allowed in MPI_Comm_rank ).
- Invalid keyval
MPI_Attr_put, MPI_Keyval_create, MPI_Attr_delete, MPI_Comm_get_attr