Communicator to which attribute is attached (handle).
.TP 1i
keyval
Key value (integer).
.SH OUTPUT PARAMETERS
.ft R
.TP 1i
attribute_val
Attribute value, unless flag = false.
.TP 1i
flag
True if an attribute value was extracted; false if no attribute is associated with the key.
.ft R
.TP 1i
IERROR
Fortran only: Error status (integer).
.SH DESCRIPTION
.ft R
Note that use of this routine is \fIdeprecated\fP as of MPI-2. Please use MPI_Comm_get_attr instead.
.sp
This deprecated routine is not available in C++.
.sp
Retrieves attribute value by key. The call is erroneous if there is no key
with value keyval. On the other hand, the call is correct if the key value exists, but no attribute is attached on comm for that key; in such case, the call returns flag = false. In particular MPI_KEYVAL_INVALID is an erroneous key value.
.SH 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.
.sp
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.
