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Hi Holly,

I've been contemplating a fully deterministic Lua. Your post[1] on lua-users was the closest thing I found, so I'm asking what progress you've made.

I'm probably going to be hacking on Lua's code anyway, and I'd be happy to do what I can to implement this.

My use-case: I'm writing a game/simulation where two networked players can execute the same user-written script, such as an AI for someone's robot. I desire to guarantee that the two players' simulation states will not go out of sync. Even if they write stupid/malicious scripts.

I wish the determinism to apply even across serialization/deserialization (e.g. Pluto[2]), so that the game can be saved/loaded at any time, new players can be added to a networked game, etc.

(To protect from stupid/malicious scripts I'll also have to implement processor-time and memory usage limits for Lua, and make sure that they're deterministic from the simulation's point of view. I think the limits will be per-robot. Each robot could have its own lua_state to make the accounting easier. Perhaps a count of bytecodes executed, and some reasonable count of reachable data, is the way to go. And I'll do something about worst-case hash-table performance.)