Monte Carlo particle transport is a <i>big</i> application. It&#x27;s very similar to ray tracing (ray tracing for rendering is really a special case of particle transport, specific to photons with simplified physics), except that the interactions are a lot more complicated. This is a very important task in a lot of HPC fields like astrophysics, nuclear physics etc and it isn&#x27;t as well suited to CUDA style parallelism because the obvious minimum unit of computation (a single particle) has a lot of branching and data lookups. Phi is probably a bit better suited, though it still has issues with all the data lookups, which aren&#x27;t very amenable to caching strategies that might otherwise help.