rust-determinism-audit

name	rust-determinism-audit
description	Fast inline determinism sweep for ironnest Rust — greps for cross-platform hazards (f32, HashMap, transcendentals, FMA, RNG, threads, wall-clock) and runs the clippy gate. Use before committing placement-path changes.

Rust determinism audit (inline)

Determinism is ironnest's product: byte-identical placements on every shipped platform. Run this quick sweep before committing changes to geo / cde / optimizer or any placement-deciding code. For a deeper, delegated review use the determinism-auditor subagent instead.

1. The clippy gate (mechanical — encodes the rules)

cargo clippy --all-targets -- -D warnings

Any disallowed_types / disallowed_methods hit is a determinism violation defined in clippy.toml. Fix it — do not #[allow] it.

2. Grep for hazards clippy can't fully see

rg -n --type rust \
  -e '\bf32\b' -e 'NotNan<f32>' \
  -e '\bHashMap\b' -e '\bHashSet\b' \
  -e 'sin_cos|\.sin\(|\.cos\(|\.tan\(|atan2|powf|\.exp\(|\.ln\(' \
  -e 'mul_add|_algebraic|fast.?math' \
  -e 'rand::random|thread_rng|StdRng|getrandom' \
  -e 'par_iter|par_sort|par_bridge|rayon' \
  -e 'Instant::now|SystemTime::now' \
  -e 'target-cpu\s*=\s*.native.'

3. Triage each hit against the rule it touches

Hit	Rule	Allowed?
f32 on a Scalar path	width = f64	❌ (test / FFI edge only)
HashMap/HashSet where order → placement	BTree/slotmap only	❌ (debug-only assertion set OK)
sin_cos/sin/cos/atan2/powf/exp/ln	platform libm, non-portable	❌ on placement path — hardcode {0,±1} matrices or pinned libm
mul_add / _algebraic	FMA / fast-math diverge	❌ — use a*b + c
rand::random/thread_rng/getrandom	explicit seed only	❌ — seeded portable PRNG
par_*/rayon deciding placement	fixed reduction order	❌ (import-then-resort OK)
Instant::now/SystemTime::now feeding output	metadata only	❌ — constant time_stamp
+ - * / sqrt powi	IEEE-deterministic	✅

A hazard is a bug, not a tuning knob. Prove byte-stability in the cross-platform CI golden before claiming it.