jpmschweitzerandClaude Opus 4.6
d45cfe0fa3
- HashMap → BTreeMap throughout econ-sim for deterministic iteration (D-010) - Fix cost_factor: multiplicative gate×zone instead of additive (trade.rs) - Extract derive_seed to shared prng.rs, consolidate FNV-1a implementation - Rename run_shock_test → run_no_explosion_check (not D-179 Test 3) - Deduplicate cross-zone FX rate collection in Test 4 - Replace ORDER BY RANDOM() with deterministic ordering + ChaCha8Rng - Make commodity coverage failure a hard error consistent with D-175 - Fix gap-fill off-by-one (4 corps → 3 when coverage = 0) - Correct test report: EconEvent exists, location_type is body/station All four D-179 stability tests still pass. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
36 lines
1.1 KiB
Rust
36 lines
1.1 KiB
Rust
//! Shared PRNG helpers for deterministic seeding (D-176, D-174).
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//!
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//! Both seed.rs and currency.rs use the same FNV-1a mix + Box-Muller transform.
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//! Centralised here to guarantee identical derivation chains across modules.
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use std::f64::consts::PI;
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use rand::Rng;
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use rand_chacha::ChaCha8Rng;
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/// FNV-1a 64-bit offset basis.
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const FNV_OFFSET_BASIS: u64 = 0xcbf29ce484222325;
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/// FNV-1a 64-bit prime.
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const FNV_PRIME: u64 = 0x100000001b3;
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/// Deterministic per-key seed: FNV-1a of `key` mixed with `run_seed`.
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///
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/// Starting from `run_seed + FNV_OFFSET_BASIS` provides per-run variation
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/// while preserving the FNV avalanche properties across keys.
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pub fn derive_seed(run_seed: u64, key: &str) -> u64 {
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let mut h = run_seed.wrapping_add(FNV_OFFSET_BASIS);
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for byte in key.bytes() {
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h ^= byte as u64;
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h = h.wrapping_mul(FNV_PRIME);
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}
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h
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}
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/// Box-Muller transform: standard normal variate from a ChaCha8 stream.
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pub fn standard_normal(rng: &mut ChaCha8Rng) -> f64 {
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let u1: f64 = 1.0 - rng.random::<f64>(); // avoid ln(0)
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let u2: f64 = rng.random::<f64>();
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(-2.0 * u1.ln()).sqrt() * (2.0 * PI * u2).cos()
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}
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