alt Hacker News> Why 'nasty'? I agree it's a problem to solve, but you just use a fixed-point math library and it's fine.
Assuming the agent didn't put in a native nondeterministic trig function deep in the code instead of using the library one, it's an easy mistake to make and hard to debug in a big game. It won't even show unless you have a robust CI matrix. It can indeed be "nasty" to maintain.
Also determinism might work for simulation state, but shader/gfx differences across platforms can be really nasty and a library can't save you. Not even something like WebGPU. Also if you're doing any sort residency streaming dependent on GPU timings trying to make that deterministic will be a nightmare.
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But that CI is very easy to setup.
Take a given start point; feed a set of inputs; compute a checksum on the resulting state. Check that the checksum matches on different platforms.
And if your language is good you can parameterize your logic on a particular numeric type, so that a particular fixed point implementation is consistently used
Unless the GPU output is feeding back into the game loop simulation, there’s no nightmare.
I’ve worked on games with intentional determinism, and it’s a very valuable tool. A playtester can hand a dev a recording of the game inputs (including clock) for whatever bug they encountered, and the dev can fast forward to the exact point and repro it 100%. The amount of time saved chasing down difficult bugs is enormous.