Second-pass self-review found a new critical issue: under "diagnostic =
clamp engagement", post-clamp diagnostics (Mech 9 weights, Mech 5 Adam
m/v slots 36-43, slots 44-45) NEVER fire — because post-clamp |v| ≤
bound by construction, so producer-side comparison always returns false.
Fix: split diagnostic implementation by clamp location.
- Buffer-based clamps (Mech 1, 2, 10): diagnostic stays in producer
(reads pre-clamp buffer, fires when step_max > bound).
- In-kernel clamps (Mech 6, 9): diagnostic lives INSIDE the Adam
kernel at the clamp step. Each Adam kernel takes a `diag_slot` arg
alongside `weight_clamp_max_abs`; on clamp engagement, writes
`nan_flags_buf[diag_slot] = 1`. Idempotent per-thread store (all
threads writing 1, race-free per existing convention). No atomicAdd.
Without this fix, slots 36-45 would be dead diagnostics under SP4 —
detecting nothing, providing no signal. With this fix, every diagnostic
slot fires on its corresponding clamp engagement regardless of where
the clamp lives.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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