# round 39 track a — qsa upstream fixes and local merge experiment

## decision

- keep `831ba47a`'s clamped-row/unconditional-load/value-select fix in the four non-cooperative prompt fills. preserve our staged scales and cooperative paths.
- keep `ad734531`'s `TK = 64` default and explicit `v2 || v3` gather/HS/binding conditions. this tree already sets `v2 = v3 = true` for `--v3`, so the binding change is documentary/defensive here, not a newly repaired v3 failure. existing half-input gather and `--gu-bench`, `--dn-bench`, `--ab`, `--dtile` remain intact.
- keep the **local** four-partial-load batching experiment in `qsa_merge2`. this is inspired by `731528be`, not a literal upstream transplant. active-chunk bounds already existed and were not changed.
- reject the exact requested six-shuffle `qsa_score` butterfly: `scores FAIL`, exit 1, on its first `--ab` case at p=3000. no speed claim for a numerically invalid candidate. cuda's reduction-order argument does not establish equivalence to metal `simd_sum`; the mismatch is measured, its compiler-level cause is not proven.
- reject four-partial batching in `qsa_merge`: bitwise correct, but nt=3 regressed repeatedly by 4.8–6.6% across all three contexts. `qsa.metal` is entirely unchanged in the delivered patch.

## artifacts and reproducibility

- patch: `/tmp/astra_r39_qsa/astra_r39_qsa.patch`
- durable copy, source snapshots, evaluators, metadata, commands, exit statuses and full logs: `results/round39/astra_r39_qsa/`
- exact baseline: the working-tree snapshot, not merely git head; `metadata.json` records its head and four owned-file sha256 values. `baseline-kernels/` and `baseline-moe_mm_parity.cpp` preserve inputs. `rejected-score.metal` and `rejected-merge1.metal` preserve rejected experiments; `final/` preserves the delivered sources.
- all editing/building ran in `/tmp/astra_r39_qsa/strata`; no tracked vendor files, live service or full-model tests were touched.
- device: apple m5; system version recorded in `metadata.json`. apple clang 21.0.0, release `-O2`. build used `cmake -S metal -B build-metal -G Ninja` followed by `cmake --build build-metal --target qsa_parity qsa_prompt_parity moe_mm_parity -j 3`.
- tests were serialized on the gpu. initial moe runs exceeded the original 15s/20s limits and were terminated; after parent explicitly extended CPU-reference allowance to 180s, both full tests completed. all unsuccessful attempts remain in the logs.
- `git -C vendor/strata apply --check /tmp/astra_r39_qsa/astra_r39_qsa.patch`: exit 0. scratch `git diff --check`: exit 0. final visual diff/context review completed.

## correctness and test results

all commands below run from the scratch tree; `BASE=/tmp/astra_r39_qsa/baseline`.

| test | result |
|---|---|
| baseline `qsa_parity --ab $BASE 3000` | exit 0, all memcmps pass |
| baseline `moe_mm_parity` | exit 3, missing `mm_gu_42_16_64_16_2` |
| final `moe_mm_parity` (no args) | exit 0, 23.961s, `PASS`; fp16-reference rel l2 2.03e-06, exact-reference 2.37e-04 |
| final `moe_mm_parity --v3 --gu IQ2_S --dn Q2_0 --tile 16,32,32,4 --dtile 64,32,2` | exit 0, 20.011s, `PASS`; fp16-reference rel l2 1.60e-05, exact-reference 4.38e-04 |
| same v3 command plus `--ab $BASE` | exit 0, HS/YE/Y memcmp pass, t=256 |
| default and specified v3 plus `--T 1` | exit 0, CPU-reference parity pass |
| v3 plus `--T 1 --gu-bench --ab $BASE`, and `--dn-bench` | both exit 0; HS/YE/Y memcmp pass; flags preserved |
| `qsa_prompt_parity` | exit 0, `ALL PASS`, default cooperative layout |
| `COOP_K4=0 qsa_prompt_parity` | exit 0, `ALL PASS`, edited non-cooperative layout |
| `qsa_prompt_parity --mm-compare attn 96 P $BASE/qsa_prompt.metal 3` | p=0 and 30000, both COOP_K4=0 and default: exit 0; output, post-timing and merge+prepared memcmp pass |
| `qsa_prompt_parity --flash-compare 96 P $BASE/qsa_prompt.metal 1 3` | same four combinations: exit 0, memcmp pass |
| `QSA_ATTN=2 qsa_parity --ab $BASE P` | p=3000,10180,30000: all full-buffer memcmps pass; nt=1,2,3,4,8 plus prompt prep nt=1984,2048 |
| `QSA_ATTN=2 qsa_parity --bitwise $BASE/qsa2.metal` | exit 0; zero of 40 cases differ, including short contexts/remainders |

important distinction: moe's no-argument and specified-v3 CPU checks are tolerance checks and print `PASS`, not `ALL PASS` or bitwise equality to CPU. the separate v3 A/B command provides bitwise equality to the baseline kernels. prompt's default suite likewise includes tolerance checks; the comparison modes provide bitwise evidence for both edited kernels. no unsupported claim of IEEE equality to a differently accumulated CPU reference is made.

## merge2 paired timings

three sweeps: initial, confirmation, then final with rejected merge1 restored. all pass. the final sweep below uses only retained changes. measurements are median GPU µs; paired ratio is median(candidate/baseline), not necessarily the quotient of medians. inspected evaluator code uses **five paired rounds**, 16 dispatch repetitions for decode (the file header's 12-repetition description is stale). each stage is warmed before interleaved A/B timing.

| p | nt | baseline µs | candidate µs | paired candidate/baseline |
|---:|---:|---:|---:|---:|
| 3000 | 1 | 15.143 | 9.273 | 0.6122 |
| 3000 | 2 | 21.924 | 21.516 | 0.9812 |
| 3000 | 3 | 33.688 | 32.969 | 0.9791 |
| 3000 | 4 | 45.458 | 43.227 | 0.9522 |
| 3000 | 8 | 91.102 | 86.547 | 0.9501 |
| 10180 | 1 | 10.961 | 6.844 | 0.6240 |
| 10180 | 2 | 21.977 | 21.589 | 0.9834 |
| 10180 | 3 | 33.732 | 32.961 | 0.9772 |
| 10180 | 4 | 45.344 | 43.313 | 0.9546 |
| 10180 | 8 | 91.393 | 86.607 | 0.9493 |
| 30000 | 1 | 17.180 | 10.807 | 0.6295 |
| 30000 | 2 | 22.125 | 21.547 | 0.9739 |
| 30000 | 3 | 33.500 | 33.471 | 0.9955 |
| 30000 | 4 | 45.469 | 43.544 | 0.9577 |
| 30000 | 8 | 91.594 | 88.021 | 0.9556 |

nt=1 improves 35–41% across the earlier sweeps and 37–39% in the final sweep; other cases are neutral to about 5% faster. one initial p=30000, nt=3 ratio was 1.0008 (0.08% noise); subsequent ratios were 0.9902 and 0.9955. no repeatable regression. absolute clocks/times drift (even unchanged stages), so use paired ratios, not cross-run raw times. this is a standalone-kernel result, not evidence of whole-model throughput improvement.

for the rejected merge1, confirmation nt=3 ratios were 1.0551, 1.0660, 1.0563 at p=3000,10180,30000. despite wins elsewhere, these violate the requested neutral-to-faster-across-suite rule.

## prompt safety fix timing observation

with `COOP_K4=0`, p=30000/t=96 non-cooperative attn median fell from 4.954 to 1.537ms, flash from 5.685 to 1.828ms, with memcmp pass. p=0 also improved. these three-pair observations are secondary to the safety fix, not broad performance claims. cooperative mode remains bitwise identical. actual m1 hardware was not available; the m1 fault rationale comes from upstream `831ba47a`, while our runtime evidence is m5 with both constant settings.