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docs(paged): record W4A16 Wq padding rejection

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Record the Phase 5 Wq shared-memory padding experiment, its gates, sub-threshold benchmark gain, and the decision to ship no 0051 patch.

Assisted-by: Codex:gpt-5
This commit is contained in:
Ettore Di Giacinto
2026-06-30 22:23:14 +00:00
parent 85c88320ef
commit f9e015d8e2
2 changed files with 90 additions and 0 deletions
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backend/cpp/llama-cpp-localai-paged/docs/GB10_PARITY_PHASE0_RESULTS.md
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`d9b9be0bee3d7239132bfca05d5b057ff4ee4cc3`.
- Tree hash after patch application: `8fcb151e0620fd0fc82b80c04318e5c34320b087`.
## W4A16 Wq Padding Phase 5
Goal: test whether padding the quantized-weight shared-memory row stride gives
another low-conflict W4A16 grouped-kernel body win after `0050`.
Artifacts:
- Build: `~/llama-w4a16-phase5`
- Logs: `~/bench/w4a16_phase5`
Gates:
- Canonical paged MoE md5: `8cb0ce23777bf55f92f63d0292c756b0`.
- Canonical dense md5: `5951a5b4d624ce891e22ab5fca9bc439`.
- Forced W4A16 `bm32` and old `base` shape md5s matched each other:
`07db32c2bcb78d17a43ed18bc22705cd`.
- Forced W4A16 `MUL_MAT_ID`: `806/806` on CUDA0.
Performance:
| Shape | 512 S_PP t/s | 2048 S_PP t/s | Decision |
|-------|--------------|---------------|----------|
| Phase 4 A-pad `bm32` | 1466.62 | 1495.93 | baseline |
| Phase 5 Wq-pad `bm32` | 1472.36 | 1504.82 | rejected: below 1% gate |
| Phase 4 A-pad `base` | 1337.88 | 1364.98 | baseline |
| Phase 5 Wq-pad `base` | 1337.70 | 1368.48 | diagnostic |
Result:
- Rejected. No fork commit and no LocalAI patch `0051`.
- The local fork experiment was reverted.
- Do not ship Wq padding alone; the measured `+0.4%` / `+0.6%` default-shape
gain is below the maintenance threshold.
## Clean Build
First clean build attempt:

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docs/superpowers/plans/2026-06-30-w4a16-wq-pad-phase5.md Normal file
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# W4A16 Wq Shared-Memory Padding Phase 5 Plan
> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development or superpowers:executing-plans. Keep checkboxes current while executing.
**Goal:** Test whether padding the grouped W4A16 quantized-weight shared-memory row stride improves the post-`0050` kernel.
**Scope:** Fork-first experiment on top of `0050`. Keep it separate and incremental. Ship no patch unless it passes md5/op gates and improves prefill.
## Task 1: Implement Wq Padding
- [x] Add a Wq shared-memory row-stride constant.
- [x] Pad Wq rows by 4 `uint32_t` slots.
- [x] Update only Wq copy and Wq byte-indexing; do not change A padding, Wd layout, dequant math, MMA order, metadata, or launch shape.
## Task 2: Gates
- [x] Build `llama-batched-bench`, `llama-completion`, and `test-backend-ops` on DGX.
- [x] Run canonical default-off paged MoE and dense greedy md5 gates.
- [x] Run forced W4A16 `bm32` vs `base` md5 gates.
- [x] Run forced W4A16 `test-backend-ops test -b CUDA0 -o MUL_MAT_ID -j 1`.
- [x] Run W4A16 default `bm32` A/B against Phase 4 at `npp=512,2048`.
## Task 3: Disposition
- [x] Keep only if it improves W4A16 prefill by at least 1% at either `npp=512` or `npp=2048` without regressing the other by more than 1%.
- [x] If kept, commit fork-first with `Assisted-by: Codex:gpt-5`, generate patch `0051`, verify mirror tree hash, update docs, and commit LocalAI. Not taken: perf gate did not clear 1%.
- [x] If rejected, revert the fork experiment and record the result without adding a patch.
Result: rejected, no fork commit and no LocalAI patch `0051`.
Artifacts:
- Build: `~/llama-w4a16-phase5`
- Logs: `~/bench/w4a16_phase5`
Gates:
- Canonical paged MoE md5: `8cb0ce23777bf55f92f63d0292c756b0`.
- Canonical dense md5: `5951a5b4d624ce891e22ab5fca9bc439`.
- Forced W4A16 `bm32` md5: `07db32c2bcb78d17a43ed18bc22705cd`.
- Forced W4A16 `base` md5: `07db32c2bcb78d17a43ed18bc22705cd`.
- Forced W4A16 `MUL_MAT_ID`: `806/806` on CUDA0.
Performance:
| Shape | 512 S_PP t/s | 2048 S_PP t/s | Decision |
|-------|--------------|---------------|----------|
| Phase 4 A-pad `bm32` | 1466.62 | 1495.93 | baseline |
| Phase 5 Wq-pad `bm32` | 1472.36 | 1504.82 | rejected: below 1% gate |
| Phase 4 A-pad `base` | 1337.88 | 1364.98 | baseline |
| Phase 5 Wq-pad `base` | 1337.70 | 1368.48 | diagnostic |
Disposition:
- Reverted local fork experiment in `/home/mudler/_git/llama.cpp`.
- Do not ship Wq padding alone; the measured gain is below the maintenance threshold.