I want cross-platform deterministic fluid simulations (at least in platforms with IEEE 2008 float semantics). What I mean is, I want to run the same software on different architectures and platforms and get the same exact answer. Is that feasible?

Also, are some techniques more amenable to cross-platform determinism while others are more challenging?

Note that Rapier can do this for mechanical simulations aimed at gamedev https://rapier.rs/docs/user_guides/rust/determinism/

Moreover: can I add threads or use SIMD or run on GPUs and still be deterministic? (Rapier can't do that: it runs on CPU, and on the cross-platform deterministic mode it disables threads and SIMD)

I'm not sure if those are considered worthwhile research lines, but this is what I care most.