Adds `kl_divergence.py`: first-token KL(stock || abliterated) over the full
248,320-token vocabulary, bf16 vs bf16, scored separately for held-out harmless
and reserved-harmful prompts.
Result (L35, 256 harmless / 104 harmful, answer mode):
harmless median 0.0211 mean 0.0364 top-1 agreement 89.8%
harmful median 0.5996 mean 0.6992 top-1 agreement 55.8%
selectivity 28.4x (72.8x in think mode)
Self-KL noise floor is exactly 0.0, and all 720 per-prompt values are
bit-identical between a single-process and a two-process run, so the figures are
signal rather than bf16 jitter. Reverse KL on harmful/answer is 1.43 vs forward
0.70 — the mass-where-stock-had-none asymmetry expected of a refusal-direction
removal. Against the Heretic reference figures (0.1191 prior seat, 0.0759 the
live absolute-heresy seat) this is materially gentler, but those are the other
tool's optimizer output on a different base with its own harmless set and
template — order-of-magnitude, not head-to-head. KL remains a fidelity number;
the viability gate is still MTP acceptance (59.1%).
Method notes:
- Prompt classes are reported separately by design. A single averaged KL over a
mixed corpus is close to meaningless, since the metric is meant to be large on
harmful prompts and small on benign ones; the ratio carries the information.
- The harmless evaluation set is drawn from the alpaca pool minus calibration's
own draw, reconstructed by replaying that draw rather than remembered, and
asserted disjoint on text. The harmful set is the reserved test split.
- `render` is imported from abliterate.py rather than copied, so the measurement
cannot drift from the rendering the direction was captured against.
- Batch size 1 with logits_to_keep=1: no padding semantics, ~0.6 MB of logits.
Three corrections to the runbook, each of which cost time:
- "bf16 is 50 GB, only gen must go" was 50.10 GiB mislabelled. Text-only weights
are 51,300 MiB; freeing either GPU0 seat alone leaves ~50,933 MiB. Both must
stop. VRAM is now sized from the safetensors headers at run time.
- A 27B model cannot be released in-process: `del` + gc + empty_cache left free
VRAM at 45,287 MiB, and so did confining the model to an inner frame that
exits. Only process exit returned the card (96,689 MiB). The first run
completed only because the allocator hit OOM, collected, and retried. Each
model now gets its own process, handing log-probs to disk between stages.
- The residency gate read hf_device_map, which transformers leaves empty when the
model fits on one device — it reported "(unsharded)" whether or not anything
was wrong, so it could never fail. It now reads parameter devices directly.
Model-agnostic lessons promoted to the quant playbook (new 3.12).
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