Locking game update speed causing high CPU usage. How do I make thread sleep when not doing anything?

Question

So I'm currently just learning how to do this, and someone said that the code is inefficient because the thread is still running when nothing is updating. When I look at the CPU usage in the task manager, it shoots up to 35 - 45% and 20 in the CPU column when only a black screen is being rendered. Is there a way to make the thread sleep when the CPU isn't updating anything?

Thanks!

public void run() {

    long lastTime = System.nanoTime();
    long timer = System.currentTimeMillis();
    final double ns = 1000000000.0 / 60.0;         
    double delta = 0;

    int frames = 0;
    int updates = 0;

    while (running) {
        long now = System.nanoTime();
        delta += (now - lastTime) / ns;
        lastTime = now;
        while(delta >= 1) {
            update();
            updates++;
            delta--;
        }

        render();
        frames++;

        if(System.currentTimeMillis() - timer > 1000) {
            timer += 1000;
            updates = 0;
            frames = 0;
        }
    }
    stop(); 
}

You make a thread sleep when not updating anything by having it be event-driven vs simply sitting in a tight loop. — Hot Licks, Oct 24 '14 at 22:33
Calculate the difference between the tim it took to render/update the frame and the amount of time you might need to sleep (ie about 16 milliseconds for 60fps) then sleep (via `Thread.sleep`) for the difference... — MadProgrammer, Oct 24 '14 at 22:33
http://docs.oracle.com/javase/tutorial/essential/concurrency/sleep.html — Radiodef, Oct 25 '14 at 00:37

score 0 · Answer 1 · answered Oct 24 '14 at 22:29

0

You shouldn't render on your own threads. SWING is thread unsafe so all GUI operations should happen on the SWING thread. It just happens SWING has a thread specially made for this.

timer = new javax.swing.Timer(1000 / 60, this);
timer.start();


@Override
public void actionPerformed(ActionEvent e) {
    // Do your stuff (ignore 'e')
}

answered Oct 24 '14 at 22:29

Mark Jeronimus

9,278
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1

Since the OP has not mentioned what framework they are using, this makes a better comment then an answer – MadProgrammer Oct 24 '14 at 22:32
Since I see `render()` and 60 (fps), and with the code style, it's an educated guess. – Mark Jeronimus Oct 24 '14 at 22:34
1

But it's still only a "guess" - render could be using a `BufferedStrategy` or even some other framework...better to ask clarification avoid the potential down votes ;) – MadProgrammer Oct 24 '14 at 22:35
For reference, this looks suspiciously similar to the OP's code http://stackoverflow.com/q/25167305 – Dan Getz Oct 25 '14 at 00:44

Victor2748 · Accepted Answer · 2014-10-25T00:36:56.980

-2

The only good way of doing it, is to execute the yourThread.wait() when the game stops doing stuff, and then yourThread.notify() when the game makes an action again.

edited Oct 25 '14 at 00:36

answered Oct 24 '14 at 22:22

Victor2748

4,149
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@Acecle Np, glad if this helps. Also don't forget to mark this question as "accepted" if it helps – Victor2748 Oct 24 '14 at 22:28
1

That's not what `.start()` does. It's used only to start the thread the first time, not to break a call to `sleep()`. – Dan Getz Oct 25 '14 at 00:27
@DanGetz oops, My bad! Ill fix it – Victor2748 Oct 25 '14 at 00:28
1

This is just wrong. You shouldn't write answers if you don't understand the subject matter. – Radiodef Oct 25 '14 at 00:36

Locking game update speed causing high CPU usage. How do I make thread sleep when not doing anything?

2 Answers2