[OpenLayers-Dev] lib evaluation performance

[Eric Lemoine]

Hi

To follow up on <http://trac.osgeo.org/openlayers/ticket/2899> I've
run experiments to evaluate the time it takes for the browser's js
engine to do the initial evaluation of the library.

I've run experiments with three versions of the library:

- "Old-style class" - in this version the old OpenLayers.Class
implementation is used (prior to changeset 10858)

- "New-style class" - in this version the new OpenLayers.Class
implementation is used. This version is the current trunk.

- "Inherit" - in this version all type definitions are converted from
using OpenLayers.Class to using pure JavaScript and OpenLayers.inherit
for base types and sub-types, respectively.

The evaluation time is measured by adding timestamps (new Date) at the
beginning and end of a "full" OpenLayers.js build.

Here are the results for a number of browsers:

--------------
FF 4 Nightly
Old-style class: 30ms
New-style class: 20ms
Inherit : 18ms

FF 3
Old-style class: 37ms
New-style class: 30ms
Inherit: 27ms

Chrome 7
Old-style class: ~40ms (very unstable, from 26ms to 80ms)
New-style class: ~30ms (very unstable)
Inherit: ~30ms (very unstable)

IE 7
Old-style class: 47ms
New-style class: 31ms
Inherit: 15ms or 30ms

IE 6
Old-style clas : 78ms
New-style class : 35ms
Inherit: 15ms or 30ms

Safari 3:
Old-style class : 25ms
New-style class: 18ms (unstable)
Inherit: 15ms (unstable)
--------------

The results show that not only does the new OpenLayers.Class
implementation improve "runtime" performance it also leads to a
smaller evaluation time, when compared to the old OpenLayers.Class.
That's good. "Inherit" reduces evaluation time even more, but this
isn't significant.

With these results, and taken into account that OpenLayers.Class isn't
needed anymore now that we have OpenLayers.inherit, I'd like to
propose to remove OpenLayers.Class entirely in our OpenLayers 3 Github
repository. This change cannot be done in 2.x as it will break
application code defining classes using OpenLayers.Class, this is
because the constructors no longer have an "initialize" method in
their prototypes.

I have a patch ready, see
<http://erilem.net/patches/openlayers/patch-openlayers-2899.diff>. All
tests pass. I just still need to update some of the examples, so they
use OpenLayers.inherit instead of OpenLayers.Class when definiting
specific types. I couldn't attach the patch to a track ticket because
its size exceeds the limit.

Thanks,

--
Eric Lemoine

Camptocamp France SAS
Savoie Technolac, BP 352
73377 Le Bourget du Lac, Cedex

Tel : 00 33 4 79 44 44 96
Mail : eric.lemoine at camptocamp.com
http://www.camptocamp.com