code wiki / _hdl_build / nx_lockstep.nx
nx_lockstep.nx source
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1// nx_lockstep.nx -- N-R2: sovereign DETERMINISTIC LOCKSTEP core (P2 networking, the RTS netcode model).
2// Lockstep = every client runs the SAME deterministic simulation on the SAME inputs, so only inputs cross
3// the wire (tiny bandwidth) and all clients stay byte-identical. ls_update is a pure-integer deterministic
4// step; ls_checksum hashes world state so a DESYNC (any divergence) is detectable by comparing checksums.
5// Pure integer logic -> reproducible by construction. 100% sovereign. license_tier: ORIGINAL
6
7// advance the world one tick from a single shared input. Deterministic: same (state,input) -> same state.
8func ls_update(state: *i64, k: i64, input: i64) -> i64 {
9 var i: i64 = 0
10 while i < k {
11 state[2*i] = state[2*i] + (((input + i) % 3) - 1)
12 state[2*i + 1] = state[2*i + 1] + (((input * (i + 1)) % 3) - 1)
13 i = i + 1
14 }
15 return 0
16}
17
18// deterministic checksum of world state (polynomial rolling hash; i64 wraps). Different state -> (almost
19// always) different checksum -> the desync detector.
20func ls_checksum(state: *i64, n: i64) -> i64 {
21 var h: i64 = 0
22 var i: i64 = 0
23 while i < n { h = h * 131 + state[i]; i = i + 1 }
24 return h
25}
26
27// run nticks of the shared input stream; returns the final state checksum.
28func ls_run(state: *i64, k: i64, inputs: *i64, nticks: i64) -> i64 {
29 var t: i64 = 0
30 while t < nticks { ls_update(state, k, inputs[t]); t = t + 1 }
31 return ls_checksum(state, 2 * k)
32}