Phase 1 post-mortem traced an actual `pearl_first_observation_bootstrap`
violation in my own H6 implementation: state slot 121 wrote
`aux_softmax[env, 1] = p_up ∈ [0, 1]` with sentinel 0.5, but every
OTHER state slot uses 0 as the "no signal" baseline (zero-padding,
feature_mask, ofi-missing, mtf-missing). The encoder had to learn TWO
things about slot 121 (directional mapping + non-zero bias offset)
instead of one. Phase 2 fixes the encoding to match the project
convention BEFORE declaring H6 fully falsified.
Mechanism change
────────────────
- `aux_softmax_to_per_env_kernel.cu` writes `2*p_up - 1 ∈ [-1, +1]`
instead of `p_up`. Still structurally bounded (softmax components
in [0, 1] sum to 1).
- Cold-start + FoldReset sentinel: 0.5 → 0.0 via the same pure-GPU
`fill_f32` path. No HtoD per
`feedback_no_htod_htoh_only_mapped_pinned`.
- NULL-fallback in 3 state-gather kernels (training +
backtest-per-step + backtest-chunk): 0.5f → 0.0f.
- Constant + device-function comment updates to document the
recentered encoding.
Atomic per `feedback_no_partial_refactor`: the encoding contract
spans 5 source files; partial migration produces inconsistent slot
semantics between training and eval.
Verification gates (all clean)
──────────────────────────────
- cargo check -p ml --features cuda: 0 errors, 21 pre-existing warnings
(parity with Phase 1 baseline)
- gpu_backtest_validation: 4/4 expected-passing tests still pass; 2
pre-existing PnL-assertion failures bit-identical to Phase 1
(confirms recentering does not perturb scripted-policy paths)
- compute-sanitizer --tool=memcheck: ERROR SUMMARY: 0 errors
Smoke dispatch deferred pending an orthogonal investigation into the
2 pre-existing gpu_backtest_validation failures (stale action
constants in the tests; addressed in a follow-up commit, NOT a
Phase 2 regression).
Verdict criteria (per spec, evaluated after smoke)
──────────────────────────────────────────────────
- WR > 50.5% within 3 epochs → recentering binding, H6 + Phase 2
sufficient → justify A2.
- a_var for mag/ord/urg > 1e-3 → sub-branches gradient-coupled under
recentered signal.
- WR pinned at 50.1–50.2% → Phase 2 falsified, pivot to amplitude
scaling or deeper hypothesis.
Refs
────
- docs/plans/2026-05-12-sp22-h6-phase2-recenter.md (spec)
- docs/plans/2026-05-12-sp22-h6-phase2-recenter-runbook.md (this plan)
- pearl_first_observation_bootstrap (sentinel = 0)
- feedback_no_partial_refactor (5-file atomic)
- feedback_no_htod_htoh_only_mapped_pinned (fill_f32, not HtoD)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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