You need the = sign:

&lt;%= render :partial =&gt; 'form', :locals =&gt; {:f =&gt; f} %&gt;


(you had &lt;% render ....)

Rails not rendering a partial on webpage
I have an application where I need to do nearest neighbor, rectangle/polygon overlap and other basic computational geometry operations against dynamically changing data (all 2d.)  I understand the basic data structures in the static case (quadtrees, 2-dimensional Kd-trees, R-trees, BSP, etc.) but I want to understand the state of the art in the dynamic case.  The difficulty seems to be knowning when/how to balance on insertion and deletion.  For example, is there a dynamic data structure that answers k-nearest neighbors against n points in O(log n + k), where insertion and deletion take O(log n) (amortized, maybe)?  Is there a standard reference that summarizes what's known about this problem?
