Node.js: alternative to setInterval which is more precise for game loop

Question

My setup is a multiplayer game, with sockets to async transfer data.

Now because of the nature of a game, I have a game loop which should tick every 500ms to do player updating (e.g. position, appearance,...).

var self = this;

this.gameLoop = setInterval(function()
{   
    for (var i = 0; i < playerSize; i++)
    {
        self.players.get(i).update();
    };
}, 500);

I'm currently using setInterval but when i did some benchmarks with about 200 connections, setInterval drifted away to 1000ms instead of 500ms, which makes the whole game appear laggy. Also it's not accurate enough unfortunately with a little amount of players. (note that the update calls only take about 100ms maximum)

So to me after researching, there seems to be no other option then to spawn a process which only handles the timining mechanism? Or are there other options?

Anyone has done this before or can give some fundamental ideas/solutions on how to do this?

Full code:

Game.prototype.start = function()
{
    var average = 0;
    var cycles = 10;
    var prev = Date.now();

    this.thread = setInterval(function()
    {       
        console.log("interval time="+(Date.now() - prev));
        prev = Date.now();

        var s = Date.now();

        // EXECUTE UPDATES
    for (var i = 0; i < playerSize; i++)
    {
        self.players.get(i).update();
    };

        average += (Date.now() - s);

        cycles--;
        if(cycles == 0)
        {
            console.log("average update time: " + (average/10) + "ms");
            average = 0;
                cycles = 10;
            }
    }, 500);
}

You said `update()` only takes about 100ms. How did you benchmark this? And does it mean the whole loop with 200 players only takes 100ms or one single call of `update` takes 100ms? — basilikum, Sep 15 '15 at 14:26
Hi, all the updates of the players takes less than 100ms, my point was just to make note that it is not more than the interval time. I measured it with a Date.now() difference — Captain Obvious, Sep 15 '15 at 15:05
Can you maybe show, in code, how you measured it? I am not sure, but considering these huge differences (from 500ms to 1000ms), I would assume, that the benchmark is maybe incorrect and that your loop actually takes more time then 500ms to execute which make the intervals become longer and possible overlapping. — basilikum, Sep 15 '15 at 15:15
Ok, looks good. Could it maybe have something to do with this: http://stackoverflow.com/questions/5927284/how-can-i-make-setinterval-also-work-when-a-tab-is-inactive-in-chrome/7387953#7387953 — basilikum, Sep 15 '15 at 15:42

score 3 · Answer 1 · answered Sep 15 '15 at 14:35

Here is an article on creating an accurate node.js game loop using a combination of setTimeout() and setImmediate so things are accurate but don't use up too much CPU.

The nanoTimer timing library might work for you. From the readme it sounds like it uses a similar approach. I don't know if it's been designed with games in mind but it should be worth a try!

score 0 · Answer 2 · answered Sep 15 '15 at 14:12

0

Although I don't work with games, there is a better alternative than setInterval, as shown here. It worked well for me in a business application. I hope this helps.

answered Sep 15 '15 at 14:12

arnold

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Node.js: alternative to setInterval which is more precise for game loop

2 Answers2