Equivalent to {@link #tryComplete} but does not invoke {@link
#onCompletion(CountedCompleter)} along the completion path:
If the pending count is nonzero, decrements the count;
otherwise, similarly tries to complete this task's completer, if
one exists, else marks this task as complete. This method may be
useful in cases where {@code onCompletion} should not, or need
not, be invoked for each completer in a computation.
Equivalent to {@link #tryComplete} but does not invoke {@link #onCompletion(CountedCompleter)} along the completion path: If the pending count is nonzero, decrements the count; otherwise, similarly tries to complete this task's completer, if one exists, else marks this task as complete. This method may be useful in cases where {@code onCompletion} should not, or need not, be invoked for each completer in a computation.