There are two main reasons to take advantage of the Gpu in lattice microbes. It can simulate the stochastic chemical reaction and diffusion dynamics in parallel: one thread per voxel. For instance, an E. coli sized cell would have ~40000 voxels. It’s not quite embarrassing parallel, but close. Second, the simulation is totally memory bound so we can take advantage of fast gpu memory. The decision to use CUDA over OpenCL was made in like 2009 or so. Things have changed a lot since then. I don’t think anyone has the time or interest to port it over, unfortunately.