CODEWITHSUNDEEP
javascriptmemory-managementgarbage-collection
tau
tau

Reputation: 6749

Avoiding massive garbage collection

This is a question to get a general idea how to avoid this situation. I have potentially millions of things, each with a few floats. I have to iterate through all of them, and inside the loop I have to do some calculations.

It is something like this:

for (var i = 0; i < 10000000; i++) {
    var num1 = thing[i].x * something;
    var num2 = thing[i].y * somethingElse;
    buffer.push(num1);
    buffer.push(num2);
    var num3 = thing[i].z * something;
    var num4 = thing[i].w * somethingElse;
    buffer2.push(num3);
    buffer2.push(num4);
}

I find that my memory usage explodes into the hundreds of megabytes and the browser crashes. As you can see, there is nothing hard about what I need to do, but I just need to do it on A LOT of things. I have found that the browser correctly garbage collects the temporary floats and my memory usage drops quickly, but that is assuming the browser doesn't crash first.

Any ideas how I could get the browser to garbage collect periodically (or some similar solution) so I don't end up with a huge gob of memory that crashes the browser?

Upvotes: 2

Views: 115

Answers (3)

Lex Podgorny
Lex Podgorny

Reputation: 2950

You could try doing it in portions inside a function scope, have not tried this particular case, but pretty sure variables are garbage collected once they are out of scope:

function doPortion(nFrom, nTo) {
    for (var i = nFrom; i < nTo; i++) {
        var num1 = thing[i].x * something;
        var num2 = thing[i].y * somethingElse;
        buffer.push(num1);
        buffer.push(num2);
        var num3 = thing[i].z * something;
        var num4 = thing[i].w * somethingElse;
        buffer2.push(num3);
        buffer2.push(num4);
    }
}

var nStep = 1000;
for (var n=0; n<10000000-nStep; n += nStep) {
    doPortion(n, n+nStep);
}

Upvotes: 1

Sergei Zahharenko
Sergei Zahharenko

Reputation: 1524

If you have logic witch is repeatable, do it dynamically... where you create needed value when it's really needed:

kind of: http://jsfiddle.net/acrashik/qdxLv/2/

var something = 10, somethingElse = 20;
function buffer(i){
    var num1 = thing(i).x * something;
    var num2 = thing(i).y * somethingElse;
    return [num1, num2];
}

function thing(i){
    return {x: i*10,y:i*1.5};
}

//get needed value
buffer(20);
alert(buffer(20))

Upvotes: 2

Sergei Zahharenko
Sergei Zahharenko

Reputation: 1524

reduce this case by twice memeroy consumption, just link second buffer to first;

var buffer = [];
var buffer2 = buffer;
for (var i = 0; i < 10000000; i++) {
    var num1 = thing[i].x * something;
    var num2 = thing[i].y * somethingElse;
    buffer.push(num1);
    buffer.push(num2);
}

updating first buffer you are updating second as well

Upvotes: 0

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