SP21 Tier-3 foundation: defrost two production-frozen ISV slots that
pinned at 0 across every observed training epoch (d7bj7, xmd6b). Both
bugs in the same aggregator kernel, same structural shape: per-step
binary majority-vote indicators feeding fractional EMAs.
T3.1 — WR_EMA defrost (sp20_aggregate_inputs_kernel.cu):
- was: is_win_out = (2 * wins_count >= closed_count) ? 1 : 0
binary "majority won this step" indicator
- now: win_fraction_out = (float)wins_count / (float)closed_count
fractional in [0, 1]
- With actual val WR≈0.46, the binary signal was 0 most of the time,
pinning WR_EMA at 0 across 30+ epochs in xmd6b. EMA now converges
to population win rate.
T3.2 — HOLD_PCT_EMA defrost (same kernel, same pattern):
- was: action_is_hold_out = (hold_count * 2 > n_envs) ? 1 : 0
strict-majority indicator
- now: hold_fraction_out = (float)hold_count / (float)n_envs
- Cascade: HOLD_COST_SCALE controller compared hold_pct_ema=0 to
tgt±0.05, always saw < lower, ramped × 0.95 → clamped at floor
0.01 (the hold_cost_scale=0.0100 observation in d7bj7 logs).
T3.5 expected to cascade-fix in next training run.
- HOLD_REWARD_EMA gate preserves strict-majority semantic via
hold_fraction > 0.5f test in the consumer kernel.
Atomic across struct fields, kernel logic, Rust mirror, byte
serialization, doc tables, and 4 test files (per
feedback_no_partial_refactor):
- sp20_aggregate_inputs_kernel.cu (struct + 2 computations)
- sp20_emas_compute_kernel.cu (struct + reader + gate)
- sp20_aggregate_inputs.rs (doc table)
- sp20_emas_compute.rs (Rust struct + serialize + 3 tests)
- sp20_aggregate_inputs_test.rs (reader sig + 4 test assertions)
- sp20_emas_compute_test.rs (5 struct literal updates)
- sp20_phase1_4_wireup_test.rs (HOLD_PCT_EMA expected 0.625)
Verification:
- cargo check -p ml --tests: passes (warnings only)
- cargo test -p ml --lib sp20_emas: 6/6 unit tests pass
Pearl candidate: binary-majority aggregator over a fractional
underlying signal cannot serve as input to a fractional-target EMA.
The previous fix (commit 64bbbe418) addressed the per-bar vs segment
predicate at the producer site, but didn't notice the aggregator's
binarization step still collapsed the fraction to {0, 1}. Two bugs
in series, both now resolved.
Plan reference: docs/plans/2026-05-10-sp21-train-eval-coherence-isv-defrost.md
Tiers 3.3-3.6 remaining; T3.5 expected to cascade-fix.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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