ArcGIS javascript API, point clustering, and browser performance

By default, the ArcGIS javascript API (version 3.2, 3.3) does *not* have a clustering layer.

So if you have a lot of points (for IE8 more than 500 points!) then you may want to implement a clustering solution.

Note: you can use Feature Layers published on the ArcGIS server, however these layers do not by default have a clustering ability.  I also find that Feature Layers tend to be throttled back by the ArcGIS server admins, to about 1,000 items per request, which is not much use if you are trying to show more than 1,000 items.

I used the Clustering example from ArcGIS, and with some tweaking, have it showing all 12,000+ reservoirs in SharePoint (even in IE8 !)

here is the Clustering example:

http://help.arcgis.com/en/webapi/javascript/arcgis/jssamples/#sample/layers_point_clustering

In case this helps anyone in future:

The example clustering code from ArcGIS is not optimal – I did some optimizations to avoid repeating calculations + to avoid square roots.

For IE8 – the clustering distance changes dynamically, according to the current zoom level.

ArcGIS Performance & Browsers:

Found the following from testing:

Google Chrome can handle 4,000+ items on an ArcGIS javascript map.

IE8 only handles about 500 items on an ArcGIS javascript map.