srecord noeq StupidFib_collab(ICollab collab, int n) {
  // if n <= parallelizationThreshold, we calculate serially
  settable int parallelizationThreshold = 24;

  // main calculation function
  // (if one core, go serial, otherwise parallelize)
  long get() {
    if (collab.coresToUse() == 1)
      ret serialComputation(n);
    else
      ret collab_computeLong(collab, receiver -> new Step(n, receiver));
  }
  
  // serial version
  long serialComputation(int n) {
    ret stupidFib(n);
  }
  
  // individual calculation step for parallel version
  record noeq Step(int n, LongConsumer continuation) extends LongPairCollector is Runnable {
    // if below parallelization threshold, go serial, otherwise parallelize
    run {
      if (n < max(3, parallelizationThreshold))
        continuation.accept(serialComputation(n));
      else {
        collab.addWork(new Step(n-1, setterForA()));
        collab.addWork(new Step(n-2, setterForB()));
      }
    }
    
    // calculate and forward result when subcomputations have completed
    void complete(long a, long b) {
      continuation.accept(a+b);
    }
  }
}

Began life as a copy of #1035566