Coordinated close-out of SP3 Q-learning numerical-stability per
feedback_no_partial_refactor.
REVERT Mech 8 (slow_ema fold-boundary reset). smoke-test-rxhjh on b8a7ac6f7
showed F1 NaN at step 2300 — WORSE than the 3720 ceiling with Mech 6 alone.
Persistent slow_ema across folds was providing unintentional F1 protection
(anchored at F0's smaller grad scale → tighter Mech 6 upper_bound during F1
ramp-up). Resetting loosened the clip and accelerated Adam saturation.
Removed: reset_grad_norm_slow_ema() method + reset_for_fold call site.
Kept: grad_norm_slow_ema_pinned field (consumed by Mech 6).
Kept: Mech 6 multiplier at 100× (already restored from the 5× experiment
in the Mech 8 commit; correct steady-state value).
ADD Mech 9 (post-Adam ISV-driven weight clamp). Root cause being targeted:
cuBLAS sgemm f32 accumulator overflow at slots 26 (iqn_trunk_m) + 32
(bn_d_concat_buf) at F1 step ~3540 with INPUTS clean (slots 27, 35
unflagged). The matmul output saturates because the WEIGHT matrices have
drifted to extreme-but-finite magnitudes via Adam updates over thousands
of steps. Mech 1 (gradient clamp) and Mech 6 (grad-norm clip) bound
gradients, not parameters — neither prevents this drift.
Mech 9 clamps |p_val| ≤ 100 × Q_ABS_REF.max(1.0) inside dqn_adam_update_kernel
after the L1 proximal step. ISV-driven (slot 16, ε on multiplier per SP1
pearl). 1 OOM below slot 44-45 diagnostic threshold (1e3 × Q_ABS_REF) so
the regression sentinel retains 10× firing headroom — symmetric with
Mech 1's clamp/diagnostic ratio.
Implementation:
- dqn_adam_update_kernel: new trailing arg `weight_clamp_max_abs`.
Clamp `p_val = fminf(fmaxf(p_val, -bound), bound)` after L1 step.
- All Adam launch sites in gpu_dqn_trainer.rs: compute bound from
read_isv_signal_at(Q_ABS_REF_INDEX).max(1.0) × 100.0 host-side, pass
as final arg.
- No new ISV slots. No new kernels. No graph topology change.
Validation: deferred to one L40S smoke at the new HEAD. Expected:
- F1 trains past step 3720 (Mech-6-only ceiling) — Mech 9 closes SP3.
- F1 still NaNs at similar steps — close SP3 honestly with documented
residual pointing at SP4/SP5.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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