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foxhunt/crates
jgrusewski d42a8f4000 fix: reward-scale v_range floor + fold-boundary shrink-and-perturb
Breaks C51 stable fixed point: tight v_range → tiny Bellman shift → tiny gradient
→ Q-values stuck near zero → v_range stays tight (self-reinforcing trap).

- REWARD_SCALE_FLOOR=0.01 replaces ABS_FLOOR=1e-4 (was 1400× too small)
- v_range floor proportional to single-step reward magnitude, not Q-statistics
- Ensures Bellman projection can shift atoms by at least 1 reward unit
- Removes pessimistic Q-init bias (incompatible with adaptive v_range)

Fold transition stability:
- Shrink-and-perturb at fold boundary (alpha=0.8, sigma=0.01)
- Reduces overfit to previous fold's data distribution
- Eliminates val_Sharpe=-33 crash on fold 2/3 transitions

Result: val_Sharpe positive across all 50 epochs and 3 walk-forward folds.
Q-values grow monotonically (0→0.023), Q-gap grows 245× (2.7e-6→6.6e-4).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-12 20:25:38 +02:00
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