RecursiveAction example needs some modification, i guess?

[tushargoel86]

Hi,

Thanks for wonderful explanation but i think 'join' statement is missing when invokeAll(..) used instead of fork/compute/call at line 44 in SumAction.java otherwise it prints mothing.

Please correct me if i am wrong.

Br..
Tushar Goel

[eh3rrera]

Hi Tushar,

Sorry for the late response.

If I comment lines 39 to 41 of SumAction.java and uncomment line 44, the results are printed:

   @Override
    protected void compute() {
        if (data.size() <= SEQUENTIAL_THRESHOLD) { // base case
            long sum = computeSumDirectly();
            System.out.format("Sum of %s: %d\n", data.toString(), sum);
        } else { // recursive case
            // Calculate new range
            int mid = data.size() / 2;
            SumAction firstSubtask =
                    new SumAction(data.subList(0, mid));
            SumAction secondSubtask =
                    new SumAction(data.subList(mid, data.size()));

            //firstSubtask.fork(); // queue the first task
            //secondSubtask.compute(); // compute the second task
            //firstSubtask.join(); // wait for the first task result

            // Or simply call
            invokeAll(firstSubtask, secondSubtask);
        }
    }

join is called inside invokeAll, so we don't have to call it again. If we were talking about Tasks, yes, for Tasks we have to call join because this method returns the result of the computation when it is done: https://stackoverflow.com/questions/48634809/why-should-we-call-join-after-invokeall-method