MPI_Comm_set_attr stores the stipulated attribute value \fIattribute_val\fP for subsequent retrieval by MPI_Comm_get_attr. If the value is already present, then the outcome is as if MPI_Comm_delete_attr was first called to delete the previous value (and the callback function delete_fn was executed), and a new value was next stored. The call is erroneous if there is no key with value \fIcomm_keyval\fP; in particular MPI_KEYVAL_INVALID is an erroneous key value. The call will fail if the delete_fn function returned an error code other than MPI_SUCCESS.
This function replaces MPI_Attr_put, the use of which is deprecated. The C binding is identical. The Fortran binding differs in that \fIattribute_val\fP is an address-sized integer.
The type of the attribute value depends on whether C or Fortran is being used. In C, an attribute value is a pointer (void *); in Fortran, it is a single, address-size integer system for which a pointer does not fit in an integer.
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.
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.
