869680 - Firefox javascript "array" position swapping 10-20 times slower than Chrome when using an object as an array

Status: RESOLVED DUPLICATE of bug 827490

(Core :: JavaScript Engine, defect)

Description

[Marc]

User Agent: Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.63 Safari/537.31

Steps to reproduce:

http://jsperf.com/array-memory-access-optimization

I'm changing the view on a 3D grid by swapping values around. My focus was in comparing between Chrome and Firefox performance more than comparing the performance difference between the two tests shown on jsperf.



Actual results:

Firefox is anywhere between 10-20 times slower than Chrome for the same tests


Expected results:

Would have expected a smaller performance gap between the two browsers.

Comment 1

[Till Schneidereit [:till]]

Firefox Nightly is a lot faster for me than Chrome 26:

Browser  FF     Chrome
Writing  38.66  16.37
Reading  48.85  30.06

Comment 2

[Jan de Mooij [:jandem]]

Pretty sure this is bug 827490 (should be fixed in Firefox 21, will be released next week).

Simple workaround is to use [] instead of {} here:

    var axial_view = {};

and here:

    var sagittal_view = {};