Question

I’m working on some fast looping for a project, and I decided to throw together a simple test to see how the performance varied when comparing runnning a more complex inner loop, vs. running several simple inner loops. Here is the jsperf for it:

http://jsperf.com/nested-fors-vs-iterative-fors

I’m surprised at how significant the difference appears to be.

Can anyone either point out why my test is bad (which may well be the case), or explain why the performance difference.

Thanks!

idb

Answer 1

I don’t know why you need underscore.js and jQuery for this. I’ve written a non-library version that compares:

1. 100 loops of 10 loops of 1 call each (1,000 calls)
2. 100 loops of 10 calls (1,000 calls)
3. 200 loops of 5 calls (1.000 calls)
4. 1,000 loops of 1 call (1,000 calls)

The performance of each is pretty similar.

I think your issue is that the first case is 100 anonymous functions making 10 calls each. The second is 1,000 anonymous functions making one call each. The overhead is likely in creating the anonymous functions (though I have not looked at the related internal parts of the libraries being used).