srecord noeq StupidFib_collab(ICollab collab, int n) {
  double timeout = 10.0;
  
  // if n <= parallelizationThreshold, we calculate serially
  gettable int parallelizationThreshold = 8;
  settable int delay = 0; // millisecond delay per add
  
  selfType parallelizationThreshold(int x) {
    parallelizationThreshold = max(3, x); this;
  }
  
  record noeq Step(int n, LongConsumer continuation) is Runnable {
    run {
      // fallback to serial case
      if (n < parallelizationThreshold)
        ret with continuation.accept(stupidFib(n));

      LongPairCollector collector = new {
        void complete(long a, long b) {
          continuation.accept(add(a, b));
        }
      };
      
      collab.addWork(new Step(n-1, collector.setterForA()));
      collab.addWork(new Step(n-2, collector.setterForB()));
    }
  }
  
  long get() {
    new Var<Long> var;
    collab.addWork(new Step(n, result -> {
      var.set(result);
      collab.done();
    }));
    collab.run();
    ret waitForVarToBeNotNullWithTimeout(var, secondsToMS_int(timeout));
  }
  
  long add(long a, long b) {
    if (delay > 0) sleep(delay);
    ret a+b;
  }  
}