Running evofighters on a gpu

[deontologician]

Looks like this isn't super feasible right now, but to track what kinds of options are out there:

1. Rewrite main encounter code in cuda/opencl (nope, don't feel like it)
2. Use something like rlsl or inspirv-rust to compile the main encounter code to a kernel to run on a gpu (SPIR-V is an intermediate language compiled by a gpu driver, and is fairly well supported vs older methods of telling the gpu what to do

I think if these projects get off the ground, it could be very feasible to move the main simulation code into a gpu kernel. The main issue at the moment is:

• these project's maturity is very low
• they rely on unstable features of the rust compiler
• they go straight from MIR -> SPIR-V, and so don't gain the optimization benefits available to LLVM (which is currently where most rust optimization comes from. I believe there are very few optis in Rust -> MIR) so the kernel could be significantly slower
• SPIR-V doesn't represent everything from rust super well, it might require a huge rewrite