I implemented fast parallel reduction on the GPU with WebGL

Hi guys. For the purpose of demonstrating the GPGPU capabilities of the WebGL framework regl(https://github.com/mikolalysenko/regl), I implemented this parallel reduction algorithm on the GPU. Even if I run it on my silly integrated graphics card, the GPU is like four times faster than the CPU.

Yet the implementation is just a simple full-screen shader that is run for a couple of passes. You can see the source code here: https://github.com/mikolalysenko/regl/blob/gh-pages/example/...

In case you are not familiar with parallel reduction, I will explain it here: given some elements x0, x1, x2,..., and a binary operator 'op', the parallel reduction becomes 'op(x0, op(x1, op(x2,...) ))'. For example, given the elements 4, 2, 4, 1, and the operator '+', the parallel reduction will be 11, which is just the sum of the elements.

So parallel reduction can for instance be used to compute the maximum, sum, or minimum of a list of elements. It is a very important component for many parallel algorithms. These kinds of parallel algorithms on the GPU is what makes Google's TensorFlow library so fast.