ml_core::cuda_autograd::init::generate_uniform (backing xavier_uniform,
kaiming_uniform, bias_uniform, near_zero_xavier) defaulted to seeding
from SystemTime::now() + thread_id, producing non-reproducible weights
across processes. Mamba2 stacks initialise via OwnedGpuLinear::xavier,
which routes through this helper — so PerceptionTrainer.evaluate output
diverged 5-30% across fresh-process runs with identical cfg.seed.
Fix: thread-local seedable RNG override. New API:
let _g = ml_core::cuda_autograd::init::scoped_init_seed(seed);
// ... all xavier/kaiming/bias/near_zero calls draw from
// StdRng::seed_from_u64(seed) chain while _g is alive ...
// _g dropped here -> restores default time-based seeding
PerceptionTrainer::new now installs the guard before any Mamba2Block
construction, so the trainer is reproducible from cfg.seed end-to-end.
CfC/VSN/heads already used explicit ChaCha8Rng::seed_from_u64 — only
Mamba2 was affected.
Production behavior unchanged when no guard is set. ml-core: 306 tests
pass, ml-alpha: 34 lib tests pass.
Regression test: crates/ml-alpha/tests/perception_forward_golden.rs
captures bit-exact PerceptionTrainer.evaluate output (loss + 160 probs
on a deterministic seed=42 fixture) into a 644-byte golden file.
Three consecutive runs now produce max_abs_diff=0; pre-fix runs varied
by 0.1-0.3 absolute on individual probs.
.gitignore: added exception for crates/ml-alpha/tests/fixtures/*.bin
so deterministic test fixtures land in repo.
Per pearl_scoped_init_seed_for_reproducibility in project memory.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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