{"id":4322,"job_id":8898,"problem_id":6,"lane_id":null,"type":"explore","user_id":90,"model":"claude-opus-5-5","provider":"anthropic","report_md":"# Job 8898 (route 290 direction): gen_sweep v2 tricks ported to #4107's d2 sweep_fast\n\n## Question and gate\nThe d2 (132 B) pipeline of #4107/#4117 spends most of its time in `sweep_fast`. Do the four tricks that gave gen_sweep v2\n1.34x (#4098) speed up sweep_fast too? The four tricks are: member 2 derived from member 1 plus the DQ constants, per-base\nconstants, one counter per exit, and work-group counter sums. The gate is identical solution and d2 record sets\n(`ab_check`, same seed) followed by an interleaved rate A/B. The kernel stays OpenCL C 1.2, so it carries to other vendors.\n\n## Findings\n- **Only one trick applies.** sweep_fast is already single-stream: member 2 is tested through XOR/sign conditions on\n  member 1's state, not stepped, and the kernel issues one atomic per solution, with no per-exit counters. So tricks 1, 3\n  and 4 have nothing to remove. Trick 2 does apply: K + W of steps 28..30 were loaded per candidate inside the branchy u\n  loop. `kernel_v3.cl` hoists them per base (`job8898-kernel_v3.diff`, 3 lines).\n- **Identity:** `ab_check`, seeds 88980001 and 88980002, 40 batches each: identical solution sets (13,352 and 13,647) and\n  identical d2 record sets (27,039 and 26,981).\n- **Sweep kernel alone** (8 batches, UHD 770): 6.42 -> 6.16 s, +4.2 %. Variants measured and dropped:\n  - also hoisting the m12 constant: +3.5 %;\n  - also hoisting steps 31/32/34/35: -24 % (register spills on Intel);\n  - hoisting steps 28-29 only: +2.0 %;\n  - hoisting step 28 only: +1.2 %.\n- **End to end:** interleaved 45 s runs, 6 seeds, order alternating, UHD 770.\n  - kernel_v2: 296.5 +- 1.0 IHV/s.\n  - kernel_v3: 305.5 +- 1.1 IHV/s.\n  - Gain: **+3.0 %**; the run-to-run spread is 0.4 %.\n  - Time split: q19/q20 (t_bij) 27 %, sweep 73 %, d2 < 1 %.\n- **Funnel of the sweep_fast u loop** (instrumented copy, seed 4242001, 14,535 bases, 4.03e10 iterations). Share of\n  iterations that pass each check:\n\n| check passed | share of iterations |\n|---|---|\n| step 27 | 10.75 % |\n| step 28 | 5.0 % |\n| step 29 pad check | 0.72 % |\n| step 31 | 0.34 % |\n\n  The per-iteration cost before step 27 dominates, and the hoist trims it.\n\n## Verification sufficiency\n- **Established:** identical outputs on two seeds; the gain was measured with interleaved order on 6 seeds.\n- **Assumed:** the same ordering on the A380 and on other vendors. Not measured here: the A380 is running a production\n  window.\n- **Not covered:** non-Intel devices. On GPUs with large register files, the spill-limited variant (more hoisted steps)\n  may win; that needs a re-measure.\n\nFiles carry the prefix `job8898-`. `kernel_v3.cl.txt` is the full kernel. `ab_rate.sh` is the rate A/B; `kb.py` and\n`prof.py` are the kernel-only timer and the funnel profiler (D2NET = the d2_net folder of #4107 plus job 8537's kernel_v2).\n\n## Next step (route 290)\nDoes kernel_v3 (per-base K+W for steps 28..30) keep its +3 % on a non-Intel OpenCL GPU, and does hoisting more steps (31, 32, 34, 35) win there instead of spilling?\nMethod: On an NVIDIA or AMD GPU, run job8898-ab_rate.sh (kernel_v2 vs kernel_v3, 6 seeds, interleaved) and the ab_check identity on 2 seeds; then add the K+W hoist of steps 31/32/34/35 and re-time the sweep alone (job8898-kb.py). Report IHV/s, the registers per thread, and the identity result.\nSuccess: Identical outputs and a measured ratio kernel_v3 / kernel_v2 (and of the wider hoist) on a non-Intel GPU. Failure: No gain (< 1 %) or outputs that differ; then the hoist is Intel-specific and the q19/q20 stage is next.\n","patch":null,"cpu_hours":0.25,"hashes":{"job8898-kb.py":"9e39ea5777225a90d85a29d3a9f24db39bc0d6c199f33bfa1de24cf2eca89a10","job8898-prof.py":"03f88a71ef9ea33f67b4d9562491f79ede323bc1c2bdfe6b7058ab780c5fd2e3","job8898-ab_rate.sh":"94f77748368b2e1ee5118542cefd51a33f445b05d021c0dd246298ca176f7f33","job8898-rate_out.txt":"42be6b070bbd1ef9a5fc1b03161129bd9267733bdd8a8f2dcd340bf153489050","job8898-rate_time.txt":"10ee46ce32c201e70357885931fbeb057e272b1a4f537e29c6121457312c8916","job8898-kernel_v3.diff":"5c7c422cd79148de831350aef1c43a0756f3222d932955b4a41115854c07c735","job8898-ab_88980001.txt":"18757122d772c63da1894fba8212ad0e832cdfa6d751f2c81411d83f4ea04ba7","job8898-ab_88980002.txt":"70622e29de7b7e42f88ee24f8354fa88d601e3efb75605882f25c36dfb28d935","job8898-kernel_v3.cl.txt":"011a36b0f5f6bc5e9294b417f467e4ee79343fedd631c7a821aec3f4616c6452","job8898-profile_counts.txt":"a32ccaab67616d436e72deafca0e184a283ceee03a7b63f93b5b7b072f8b0ec8","job8898-kernel_only_timing.txt":"a48d8d54df4baa4390f1880161cf522ee429d75db583ee9a85e016178016ab67"},"author_rung":"measured","status":"recorded","final_rung":"recorded","created_at":"2026-10-16T21:26:50.825Z","repo_url":null,"commit":null,"cites":{"files":[],"handles":[],"returns":[4107,4117,4098,4173],"messages":[]},"tokens":{"log":"summary","input":210,"models":{"claude-opus-5-5":48316},"output":48316,"source":"reported","entries":0,"cache_read":8629007,"cache_write":331420,"observed_models":[]},"paper_slug":null,"revision_path":null,"revision_sha":null,"recipe_md":"Take #4107's d2_net files with #4117's pad fix and job 8537's kernel_v2.cl; apply job8898-kernel_v3.diff. `ab_check.py` with seeds 88980001/88980002 gives the identity; `sh job8898-ab_rate.sh <d2_net> <out> <cpus>` gives the rate A/B (D2_DEVICE selects the device); `D2NET=<d2_net> python3 -I job8898-kb.py <kernel> <seed> 8` times the sweep alone.","verification":null,"target":null,"finding":null,"human_md":null,"provisional":false,"effects_applied_at":null,"effort":"high","also_fix":null,"transcript_omitted":{"share":0,"omitted":0,"outputs":0},"patch_hash":null,"superseded_by":null,"duplicate_of":null,"transcript_resubmitted_at":null,"file_notes":null,"research":null,"research_route_id":null,"verification_plan":null,"verification_fingerprint":null,"review_admitted_at":null,"department_id":"dept_2a239d5b5a891d355de5bb8e","run_id":"run_430d453bed36922a375152b5","triage_lead":null,"revision_base_sha":null,"integration":null,"resolves":null,"paper_exposition":null,"research_evidence":null,"transcript_mode":"summary","known_work":null,"work_disposition":null,"applicability_assessment":null,"negative_result":null,"first_indexed_at":null,"index_held_at":null,"index_ok":null,"index_reason":null,"handle":"sundayweaver","job_brief":"Consult the relevant shared local evidence. 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