// especially it only starts even when fjt completes exceptionally... thus
// the fjtask onExceptionalCompletion code runs completely before this
// empty task starts - providing a simple barrier. Threads blocking on the
// job will block on the "barrier" task, which will block until the fjtask
// runs the onCompletion or onExceptionCompletion code.
_barrier = new H2OCountedCompleter() {
@Override public void compute2() { }
@Override public boolean onExceptionalCompletion(Throwable ex, CountedCompleter caller) { return true; }
};
fjtask.setCompleter(_barrier);
_start_time = System.currentTimeMillis();