Hey all,
I got into shading recently and I'm currently trying to figure out how to 
implement the stream reduction operation.  Basically, the size of a stream 
(texture) would be reduced by half (or some other factor) until the stream 
becomes 1x1.  In each pass, a reduction operator is applied.  A reduction 
operator can be something as simple as addition.  In this case, the 
reduction operation is effectively an array sum.

This is trivial to implement on CPUs, however, I'm still in the confusion 
stage of learning about GPU and open GL shaders.  Can someone show me some 
sample code to implement this basic operation?  Thanks!

J