How to synchronize two async task?

Question

My problem is that I have two async tasks which doing a kind of matrix multiplications. Therefore both tasks are accessing the same matrix. One the upper part, the other the lower part. For memory saving issues I use ArrayLists and delete entries which I do not need longer. The problem is that in both tasks there is for loop runing and at the end of this loop it should wait for the other task. But I do not know how to do this. Task 1:

protected Void doInBackground(Void... paramArrayOfParams) {
        android.os.Debug.waitForDebugger();
        for(j=1; j<(size+1); j++)
        {
            .... 
            try{ othertask.wait();
            }catch(InterruptedException e){}
            //wait for other task();
        }

Task 2:

protected Void doInBackground(Void... paramArrayOfParams) {
            android.os.Debug.waitForDebugger();
            for(j=1; j<(size+1); j++)
            {
                ....
                notifyAll();
                //notifythatroundisfinished();
            }

I tried to use notify and wait, but it seems that this is not solving the issue. I do not know any additional methods which I could use to solve the issue. Is it actually possible to wait two for the other task while both are running?

score 1 · Answer 1 · edited May 23 '17 at 12:31

1

I believe the answer to questions below can provide you about the abstract information on how to manage multiple Async tasks.

How to manage multiple Async Tasks efficiently in Android

Running multiple AsyncTasks at the same time -- not possible?

and github example:

https://github.com/vitkhudenko/test_asynctask (credits to: vitkhudenko)

edited May 23 '17 at 12:31

Community

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answered Sep 20 '13 at 10:07

Jeremy

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I was already looking through these links and I didn't found an answer before, that's why I was posting this question. I need a synchronization which waits at the end of each for loop run, till the other task is at the same position and then both will start with the next run of the for loop. – Irgendw Pointer Sep 20 '13 at 10:33

OldCurmudgeon · Accepted Answer · 2013-09-20T10:20:03.810

0

If this is Java-7 you are looking for a Phaser. The method you need is arriveAndAwaitAdvance.

In earlier versions of Java (5.1 or later) you would probably use a Semaphore.

Alternatively - you could switch to using a thread pool such as an ExecutorService and Futures. This would be much more scalable and take better advantage of the a multi-core processor.

edited Sep 20 '13 at 10:20

answered Sep 20 '13 at 10:10

OldCurmudgeon

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I'm looking for android async task compatible solutions. – Irgendw Pointer Sep 20 '13 at 10:35
Then perhaps I was right suggesting a [Semaphore](http://developer.android.com/reference/java/util/concurrent/Semaphore.html). – OldCurmudgeon Sep 20 '13 at 10:40
Why was this answer marked as correct? I experience issues with Android's internal looper. The asyc thread is blocked if I call await() in one thread. – Jakob Alexander Eichler Mar 18 '15 at 19:53

How to synchronize two async task?

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