// Exception occurred when processing this task locally, set exception and
// send it back to the caller. Can be called lots of times (e.g., once per
// MRTask.map call that throws).
@Override
public boolean onExceptionalCompletion(Throwable ex, CountedCompleter caller) {
if (_computed) return false;
synchronized (this) { // Filter dup calls to onExCompletion
if (_computed) return false;
_computed = true;
}
_dt.setException(ex);
sendAck();
return false;
}
