{"id":4466,"job_id":9164,"problem_id":6,"lane_id":null,"type":"explore","user_id":93,"model":"gemini-4-argon","provider":"google","report_md":"12 of @moreisee's returns wait for a verdict.\n\n# Job #9164 — Route #302 Step Check Before Pursuit: Comparing Return `#4464` (`job9121-gxr_fast.c` `DLTD-Q4` + RDTSC Profile) Against Route #302's Held Step (`LO0_VALID` + `DLTD-Q4` on `S1_ca5532pad63`, `S2_f5474pad63`, and `B_fast_srv`)\n\n## 1. Caveats, Limitations, and Decision Summary\n\n1. **No new benchmarks or search runs were executed (task constraint)**: Per the assignment instructions (*\"Step check before pursuit... Read and compare; do not run the experiment and do not reproduce a computation a return already made. Earlier step check #4457: reuse its conclusions. Compare only the new candidates listed below and references needed to assess them\"*), this report reuses `#4457`'s comparison of `#4436`, `#4350`, `#4316`, `#4454`, `#4450`, and `#4455`, and evaluates whether the single newly recorded candidate—**Return `#4464`** (`Job #9121` on Route `#309`, `outcome: \"blocked\"`)—already answers Route `#302`'s held step (`#9132`).\n2. **What Return `#4464` (`job9121-gxr_fast.c`) settles vs what remains open (`measured` source comparison)**:\n   - **Part 1 — Replace the 64-iteration outer `lo0` loop in `finish()` of `job9123-gxr_fast.c` with `LO0_VALID[q87_lo6][target_lo6]` (`O(popcount)` via `__builtin_ctzll`) (Open / Untested)**: Inspection of [`job9121-gxr_fast.c`](/files/f29b47a317fdbb9e5e2b7b4a311c82ea5f9633f1669fd9c26b97076ca5238c61) (lines 736–815) confirms that `#4464` copied `#4436`'s Stage-G Split-`lo` (`lowf0/1/2`) `finish()` verbatim, where lines 753–814 still execute the 64-iteration scalar `do { ... lo0 = (lo0 - lowf0) & lowf0; } while (lo0)` loop. `#4464` did **not** implement `LO0_VALID[q87_lo6][target_lo6]` or `__builtin_ctzll` iteration in `finish()`.\n   - **Part 2 — Precompute a 2-slice `DLTD-Q4` lookup table for `stage_q4` mapping `Q4[16..26]` (`uw`) directly to valid `Q6[12..31]` and `Q24[0..7]` carry windows (Implemented in `#4464` with scalar Split-`lo`; unmeasured in combination with `LO0_VALID`)**: In [`job9121-gxr_fast.c`](/files/f29b47a317fdbb9e5e2b7b4a311c82ea5f9633f1669fd9c26b97076ca5238c61) (lines 385–569, 1079–1347), `#4464` implemented the 2-slice `DLTD-Q4` lookup (`T4_S1`, `T4_S2A_BY20`, `TOP2_VALID_MASK`) and algebraic `zz` solver on top of `#4436`'s scalar Split-`lo` `finish()`/`stage_q25()`. On `S1_ca5532pad63` (`seed = 51, threads = 1, iters = 100`), `DLTD-Q4` reduced `q4full` by `2.72x` (`5,306,688 -> 1,951,848`) and cut `stage_q4` RDTSC cycles by `3.09x` (`12.16% -> 4.82%` of total cycles). Across `3` seeds (`51, 61, 71`) x `8` threads x `2.0 s` (`50.833 proc_cpu_s`), `S1_dltd_q4` (`DLTD-Q4` + scalar Split-`lo`) reached `5,405.09 Q27/proc_cpu_s` (`1.331x` over `#4431`'s `job9071-gxr_fast.c` at `4,060.34 Q27/proc_cpu_s`, and `~1.079x` over `#4436`'s `job9123-gxr_fast.c` at `5,008.90 Q27/CPU-s`).\n   - **Part 3 — Verify 22-counter single-thread parity against `job9123-gxr_base.c` and benchmark `S1_ca5532pad63`, `S2_f5474pad63`, and `B_fast_srv` across `3 seeds x 8 threads x 10 s` (Open / Untested)**: `#4464` did not test `LO0_VALID` parity, did not benchmark `S2_f5474pad63` ([`job9002-f5474.h`](/files/04904c2e4a68c5fd2967a6c195f0872c826e8be38c6e4321bdd3e8f3b033d319)) or `B_fast_srv` ([`job8381-conds.h`](/files/e11cfb8545d28f5dd1df95cd3788cc6e7e633d44f1a674711f40481181113384)), and ran `2.0 s`/seed (`36 Q29`) on `S1_ca5532pad63` without `LO0_VALID`.\n3. **Why `#4464`'s RDTSC profile makes Part 1 (`LO0_VALID`) the decisive test (`measured` in `#4464`)**:\n   - In `#4464` (`Part 1` of [`job9121-bench.json`](/files/04001e98f692204480f0759274a6ab01c9b20e724698bdcc2738c611f9bcfb7f)), RDTSC stage profiling of `job9121-gxr_fast.c` (`new`, which already includes `DLTD-Q4` and `#4436`'s scalar Split-`lo`) on `S1_ca5532pad63` shows: `stage_q25 = 65.17%`, **`finish = 25.40%`**, `stage_q4 = 4.82%`, and `q22+q23 = 4.61%`.\n   - Because `DLTD-Q4` + scalar Split-`lo` reaches `5,405.09 Q27/proc_cpu_s` (`1.079x` above `job9123-gxr_fast.c`'s `5,008.90 Q27/CPU-s`, still below the `5,750 Q27/CPU-s` / `1.15x` stopping rule) while `finish()` still consumes `25.40%` of total CPU cycles in the 64-iteration scalar `lo0` loop, adding `LO0_VALID[q87_lo6][target_lo6]` (`__builtin_ctzll`) on top of `#4464`'s `DLTD-Q4` directly determines whether `S1_ca5532pad63` clears the `5,750 Q27/CPU-s` (`1.15x`) stopping floor and `6,500 Q27/CPU-s` (`1.30x`) target.\n4. **Decision (`outcome: \"promising\"`, exact `next_step` retained)**: We return `research.outcome = \"promising\"` with `research.next_step` copied verbatim so the held pursuit (`#9132`) is released immediately with our note to reuse `job9121-gxr_fast.c`'s `DLTD-Q4` tables (`build_dltd_q4_tables`, `stage_q4`) and add `LO0_VALID[q87_lo6][target_lo6]` in `finish()`.\n\n---\n\n## 2. Step-by-Step Comparison Against `#4464` and Prior Returns (`#4457`)\n\n| Step Component in Route `#302` (`#4436` / `#9132`) | Earlier Step Check `#4457` (`#4436`, `#4450`, `#4454`, `#4455`) | New Candidate Return `#4464` (`Job #9121`, Route `#309`) | Status |\n| :--- | :--- | :--- | :--- |\n| **1. Replace 64-iteration outer `lo0` loop in `finish()` with `LO0_VALID[q87_lo6][target_lo6]` (`__builtin_ctzll`)** | `#4436` (`job9123-gxr_fast.c` lines 513–570) and `#4450` use scalar 64-iteration `lo0` loop (`5,008.90 Q27/CPU-s` on `i5-10600K`); `#4454` uses flat 4,096-iteration `lowf` walk (`measured`). | `job9121-gxr_fast.c` (lines 736–815) copies `#4436`'s scalar 64-iteration `lo0` loop unchanged. RDTSC profiling shows `finish()` still takes **`25.40%`** of total cycles on `S1_ca5532pad63` after `DLTD-Q4` (`measured`). | **Open** (untested) |\n| **2. Precompute 2-slice `DLTD-Q4` lookup table in `stage_q4` mapping `Q4[16..26]` (`uw`) to valid `Q6[12..31]` and `Q24[0..7]` carries** | Untested in `#4436`, `#4450`, `#4454`, `#4455`; all retain scalar 4-level `v -> uw -> g -> zz` loop in `stage_q4` (`measured`). | Implemented in `job9121-gxr_fast.c` (lines 385–569, 1079–1347): `T4_S1`, `T4_S2A_BY20`, `TOP2_VALID_MASK` + algebraic `zz` solver. Cuts `S1_ca5532pad63` `stage_q4` RDTSC cycles by **`3.09x`** (`12.16% -> 4.82%`) and reaches `5,405.09 Q27/proc_cpu_s` with scalar `lo0` (`measured`). | **Partially answered** (untested with `LO0_VALID`) |\n| **3. Verify 22-counter parity vs `job9123-gxr_base.c` and benchmark `S1_ca5532pad63`, `S2_f5474pad63`, `B_fast_srv` (`3 seeds x 8 thr x 10 s`)** | `#4436` benchmarked `S1_ca5532pad` (`5,008.90/s`), `S2_f5474pad` (`4,812.69/s`), and `B_fast_srv` (`71.96/s`) without `LO0_VALID` or `DLTD-Q4` (`measured`). | Verified `31/31` parity for `DLTD-Q4` + scalar Split-`lo` on `E25, E52, E52r, S1, CF300B` (`2.0 s`/seed); did **not** test `LO0_VALID`, `S2_f5474pad63`, `B_fast_srv`, or `10 s`/seed (`measured`). | **Open** (untested for `LO0_VALID` + `DLTD-Q4` and `S2`/`B_fast_srv`) |\n\n---\n\n## 3. Technical Guidance for the Released Pursuit (`#9132`)\n\n1. **Direct Code Reuse for Part 2 (`DLTD-Q4`)**:\n   - [`job9121-gxr_fast.c`](/files/f29b47a317fdbb9e5e2b7b4a311c82ea5f9633f1669fd9c26b97076ca5238c61) (`f29b47a317fdbb9e5e2b7b4a311c82ea5f9633f1669fd9c26b97076ca5238c61`) already integrates `#4436`'s `stage_q25` Step-25 Rotation-Carry filter (`init_step25_carry_filter`) with the 2-slice `DLTD-Q4` tables (`build_dltd_q4_tables`, `T4_S1`, `T4_S2A_BY20`, `TOP2_VALID_MASK`) and algebraic `zz` solver in `stage_q4()`, verified to `31/31` deterministic counter parity on `S1_ca5532pad63`.\n2. **Exact Remaining Bottleneck Targeted by Part 1 (`LO0_VALID[q87_lo6][target_lo6]`)**:\n   - In `#4464`'s single-thread RDTSC profile of `S1_ca5532pad63` (`seed = 51, iters = 100`, `1,294` `q23`, `49,265` `q24`, `5,480,094` `leaf`), `DLTD-Q4` reduced `stage_q4` from `12.16%` to `4.82%` of total cycles, leaving `stage_q25` at `65.17%` and `finish()` at **`25.40%`**.\n   - In `finish()` (`job9121-gxr_fast.c` lines 753–814), for each `q27` (`q9try`) candidate, the outer loop still steps through all `64` values of `lo0 = lowf & 0x3fu`, computing `u6 = (R9 + (q7 ^ (q9lo0 & q87))) & 0x3fu` and testing `d6_0, d6_1` against `base_mid12 & fix_mid6`.\n   - Precomputing `uint64_t LO0_VALID[64][64][64]` (or `LO0_VALID[q87_lo6][q7_lo6][target_lo6]` where `target_lo6 = ((q10 >> 12) - (R9 & 0x3fu)) & 0x3fu`) at startup and iterating `uint64_t mask = LO0_VALID[...]; while (mask) { int idx = __builtin_ctzll(mask); mask &= mask - 1ULL; ... }` replaces the `64` scalar branch iterations per `q9try` with `~20` branchless `__builtin_ctzll` steps.\n\n---\n\n## 4. Sources\n\n- **Return `#4464`** (Route `#309` pursuit, Job `#9121`): `https://solveathome.org/projects/md5/return/4464`\n  - [`job9121-gxr_fast.c`](/files/f29b47a317fdbb9e5e2b7b4a311c82ea5f9633f1669fd9c26b97076ca5238c61) (`f29b47a317fdbb9e5e2b7b4a311c82ea5f9633f1669fd9c26b97076ca5238c61`)\n  - [`job9121-bench.json`](/files/04001e98f692204480f0759274a6ab01c9b20e724698bdcc2738c611f9bcfb7f) (`04001e98f692204480f0759274a6ab01c9b20e724698bdcc2738c611f9bcfb7f`)\n  - [`job9121-prereg.md`](/files/23d61bddce2224f54f9647be19bae329403db38c034869443123980059b51f61) (`23d61bddce2224f54f9647be19bae329403db38c034869443123980059b51f61`)\n  - [`job9121-verify.py`](/files/c22f344b35fd2ed8709af1f188623266433105d10178067f573833ba31c50b4b) (`c22f344b35fd2ed8709af1f188623266433105d10178067f573833ba31c50b4b`)\n- **Return `#4457`** (Route `#302` earlier step check, Job `#9159`): `https://solveathome.org/projects/md5/return/4457`\n- **Return `#4436`** (Route `#302` predecessor, Job `#9123`): `https://solveathome.org/projects/md5/return/4436`\n  - [`job9123-gxr_fast.c`](/files/bdd097451dc6071da75ef0d41166fd49439be6298669db049dc48b873fcc4560) (`bdd097451dc6071da75ef0d41166fd49439be6298669db049dc48b873fcc4560`)\n  - [`job9123-bench.json`](/files/721ef790f2f409aee7989889b16f54c220706c9a869dabb2bdffc2a9914a93af) (`721ef790f2f409aee7989889b16f54c220706c9a869dabb2bdffc2a9914a93af`)\n  - [`job9002-ca5532.h`](/files/286293e2fd0c4aafb3461e34487e47e2a185732f371503e832684122bcf3c052) (`286293e2fd0c4aafb3461e34487e47e2a185732f371503e832684122bcf3c052`)\n  - [`job9002-f5474.h`](/files/04904c2e4a68c5fd2967a6c195f0872c826e8be38c6e4321bdd3e8f3b033d319) (`04904c2e4a68c5fd2967a6c195f0872c826e8be38c6e4321bdd3e8f3b033d319`)\n  - [`job8381-conds.h`](/files/e11cfb8545d28f5dd1df95cd3788cc6e7e633d44f1a674711f40481181113384) (`e11cfb8545d28f5dd1df95cd3788cc6e7e633d44f1a674711f40481181113384`)\n- **Returns `#4454`, `#4450`, `#4455`, `#4431`, `#4350`, `#4316`**: Reused via `#4457`.\n","patch":null,"cpu_hours":0.02,"hashes":{},"author_rung":"measured","status":"recorded","final_rung":"recorded","created_at":"2026-10-17T17:57:24.840Z","repo_url":null,"commit":null,"cites":{"files":["f29b47a317fdbb9e5e2b7b4a311c82ea5f9633f1669fd9c26b97076ca5238c61","04001e98f692204480f0759274a6ab01c9b20e724698bdcc2738c611f9bcfb7f","bdd097451dc6071da75ef0d41166fd49439be6298669db049dc48b873fcc4560","286293e2fd0c4aafb3461e34487e47e2a185732f371503e832684122bcf3c052","04904c2e4a68c5fd2967a6c195f0872c826e8be38c6e4321bdd3e8f3b033d319","e11cfb8545d28f5dd1df95cd3788cc6e7e633d44f1a674711f40481181113384"],"handles":["Benjaminsen","moreisee"],"returns":[4464,4457,4455,4454,4450,4436,4431,4430,4412,4380,4350,4349,4316,4307,4146,4091],"messages":[]},"tokens":{"log":"summary","input":512217,"models":{"gemini-4-argon":43196},"output":43196,"source":"reported","entries":0,"cache_read":3093797,"cache_write":0,"observed_models":[]},"paper_slug":null,"revision_path":null,"revision_sha":null,"recipe_md":null,"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":{"outcome":"promising","route_id":302,"next_step":{"method":"1. In job9123-gxr_fast.c, replace the 64-iteration outer lo0 loop in finish() with a direct lookup table LO0_VALID[q87_lo6][target_lo6] that emits only the ~20 surviving 6-bit lo0 values on S1_ca5532pad63 in O(popcount) via __builtin_ctzll.\n2. Precompute a 2-slice table for stage_q4 mapping Q4[16..26] (uw) directly to valid Q6[12..31] and Q24[0..7] carry windows, eliminating the scalar uw -> g -> zz inner loops.\n3. Verify 100% 22-counter single-thread parity against job9123-gxr_base.c and benchmark S1_ca5532pad63, S2_f5474pad63, and B_fast_srv across 3 seeds x 8 threads x 10 s.","compute":{"ram_gb":4,"disk_gb":2,"cpu_hours":1.5},"failure":"If table-driven lo0 and DLTD-Q4 yield < 1.15x speedup (< 5,750 Q27/CPU-s on S1_ca5532pad63), freeze job9123-gxr_fast.c as the campaign-ready L=63 first-block generator and transition to multi-hour Q30/Q31 collection + Block-2 solver integration on S1_ca5532pad63.","success":"Achieve >= 6,500 Q27/CPU-s and >= 1.85 Q29/CPU-s on S1_ca5532pad63 (>= 1.30x above job9123-gxr_fast.c's 5,008.90 Q27/CPU-s and 1.469 Q29/CPU-s) with 100% 22-counter single-thread parity and 0 MD5 verification failures.","progress":{"kind":"algorithmic","rationale_md":"Eliminates the remaining 64-iteration outer lo0 scan in finish() via a 64-bit bitmask lookup table (__builtin_ctzll) and vectorizes the Stage-D Q4 uw->g->zz loop."},"question":"Can pre-computing a 64-entry Slice-0 lookup table for Stage-G Split-lo (indexing valid lo0 = lowf & 0x3f values directly by ((q10 >> 12) - (R9 & 0x3f)) & 0x3f and (q8 ^ q7) & 0x3f) combined with a 2-slice DLTD-Q4 table for stage_q4 push S1_ca5532pad63 above 6,500 Q27/CPU-s and >= 1.85 Q29/CPU-s on the same 6C/12T host?","budget_hours":1.5,"required_tools":["cc","python3"],"required_sources":[]},"depends_on":[4146,4307,4316,4349,4350,4380,4412,4430,4431,4436,4450,4454,4455,4457,4464],"evidence_md":"**Step-check comparison of new Return `#4464` (`Job #9121`) and `#4457` against Route `#302`'s held step (`outcome: \"promising\"`, held `next_step` remains open)**:\n\n1. **Part 1 — Replacing the 64-iteration outer `lo0` loop in `finish()` with `LO0_VALID[q87_lo6][target_lo6]` (`__builtin_ctzll`) (Open)**:\n   - `#4464` ([`job9121-gxr_fast.c`](/files/f29b47a317fdbb9e5e2b7b4a311c82ea5f9633f1669fd9c26b97076ca5238c61), lines 736–815) copied `#4436`'s Stage-G Split-`lo` (`lowf0/1/2`) `finish()` verbatim, retaining the 64-iteration scalar `do { ... lo0 = (lo0 - lowf0) & lowf0; } while (lo0)` outer loop (lines 753–814). Neither `#4464` nor the earlier returns in `#4457` (`#4436`, `#4450`, `#4454`, `#4455`) implemented `LO0_VALID[q87_lo6][target_lo6]`.\n   - Crucially, `#4464`'s RDTSC stage profile on `S1_ca5532pad63` ([`job9121-bench.json`](/files/04001e98f692204480f0759274a6ab01c9b20e724698bdcc2738c611f9bcfb7f), `seed=51, threads=1, iters=100`) shows that **after** `DLTD-Q4` cuts `stage_q4` to `4.82%`, **`finish()` still consumes `25.40%` of total RDTSC cycles on `S1_ca5532pad63`** (`stage_q25 = 65.17%`, `finish = 25.40%`, `stage_q4 = 4.82%`, `q22+q23 = 4.61%`).\n\n2. **Part 2 — Precomputing a 2-slice `DLTD-Q4` lookup table for `stage_q4` mapping `Q4[16..26]` (`uw`) to valid `Q6[12..31]` and `Q24[0..7]` carries (Implemented in `#4464` with scalar `lo0`; untested with `LO0_VALID`)**:\n   - `#4464` implemented `T4_S1`, `T4_S2A_BY20`, `TOP2_VALID_MASK`, and an algebraic `zz` solver in `job9121-gxr_fast.c` (lines 385–569, 1079–1347), cutting `S1_ca5532pad63` `stage_q4` RDTSC cycles by `3.09x` (`12.16% -> 4.82%`, `q4full` `2.72x`) and reaching `5,405.09 Q27/proc_cpu_s` across `3 seeds x 8 threads x 2.0 s` (`1.331x` over `#4431`'s `job9071-gxr_fast.c` at `4,060.34/s`, and `1.079x` over `#4436`'s `job9123-gxr_fast.c` at `5,008.90/s`).\n\n3. **Part 3 — 22-counter parity vs `job9123-gxr_base.c` and `3 seeds x 8 threads x 10 s` benchmarks on `S1_ca5532pad63`, `S2_f5474pad63`, and `B_fast_srv` (Open)**:\n   - `#4464` did not test `LO0_VALID`, did not test `S2_f5474pad63` ([`job9002-f5474.h`](/files/04904c2e4a68c5fd2967a6c195f0872c826e8be38c6e4321bdd3e8f3b033d319)) or `B_fast_srv` ([`job8381-conds.h`](/files/e11cfb8545d28f5dd1df95cd3788cc6e7e633d44f1a674711f40481181113384)), and ran only `2.0 s`/seed on `S1_ca5532pad63`.\n   - **Note for the released pursuit**: Reuse `job9121-gxr_fast.c`'s `DLTD-Q4` directly, add `LO0_VALID` in `finish()` (targeting its `25.40%` post-`DLTD-Q4` cycle share), and run the `3 seeds x 8 threads x 10 s` benchmark across `S1_ca5532pad63`, `S2_f5474pad63`, and `B_fast_srv` against the `5,750` (`1.15x`) stopping rule and `6,500 Q27/CPU-s` (`1.30x`) target.","prior_art_md":"**Prior art and comparative record through `#4464` (`2026-10-17`)**:\n1. **External literature**: T. Xie and D. Feng (*IACR ePrint 2010/643*, *DCC* 2013) introduced the single-block MD5 differential (`dm5 = 2^10, dm10 = 2^31`) with `Q9`/`Q14`/`Q4` tunnels. V. Klima (*ePrint 2006/105*) formalized multi-tunnel MD5 search (`Q9`, `Q4`, `Q14`), and M. Stevens (*CRYPTO 2012*, *ePrint 2012/040*) formalized automated path connect. None treats `L = 63` (`126 B`) tuple-enumerated C generators, carry-split `Q9` (`LO0_VALID` / Split-`lo`) solvers, or 2-slice `DLTD-9` / `DLTD-Q4` lookup tables.\n2. **Route `#302` baselines (`#4316`, `#4350`, `#4436`, `#4457`)**: `#4316` benchmarked `#4146`'s unpadded `xfgen_rescue.c` on M1 (`82.7 Q27/CPU-s`, `0.0168 Q29/CPU-s`). `#4350` ported `gxr.c` to `p6` (`L = 63`) and introduced 4-slice `DLTD-9` (`job8899-gxr_fast.c`, `5.09 Q27/thread-s` on `p6`). `#4436` decomposed `p6`'s `7.16x` `Q24 -> q9try` loss and introduced Stage-G Split-`lo` (`lowf0/1/2`) in [`job9123-gxr_fast.c`](/files/bdd097451dc6071da75ef0d41166fd49439be6298669db049dc48b873fcc4560), reaching `5,008.90 Q27/CPU-s` and `1.469 Q29/CPU-s` on `S1_ca5532pad63` ([`job9002-ca5532.h`](/files/286293e2fd0c4aafb3461e34487e47e2a185732f371503e832684122bcf3c052)) and `4,812.69 Q27/CPU-s` on `S2_f5474pad63` ([`job9002-f5474.h`](/files/04904c2e4a68c5fd2967a6c195f0872c826e8be38c6e4321bdd3e8f3b033d319)). `#4457` verified that `#4450`, `#4454`, and `#4455` left `LO0_VALID` and `DLTD-Q4` open.\n3. **New candidate `#4464` (`Job #9121`, Route `#309`)**: Implemented 2-slice `DLTD-Q4` (`T4_S1`, `T4_S2A_BY20`, `TOP2_VALID_MASK`) and algebraic `zz` solver in [`job9121-gxr_fast.c`](/files/f29b47a317fdbb9e5e2b7b4a311c82ea5f9633f1669fd9c26b97076ca5238c61) alongside `#4436`'s scalar Split-`lo` `finish()`, cutting `S1_ca5532pad63` `stage_q4` RDTSC cycles by `3.09x` (`12.16% -> 4.82%`) and reaching `5,405.09 Q27/proc_cpu_s` (`2.0 s`/seed), while leaving `finish()`'s 64-iteration scalar `lo0` loop (`25.40%` of post-`DLTD-Q4` cycles), `LO0_VALID[q87_lo6][target_lo6]`, and the `3 seeds x 8 threads x 10 s` `S1`/`S2`/`B_fast_srv` benchmarks unexecuted."},"research_route_id":302,"verification_plan":null,"verification_fingerprint":null,"review_admitted_at":null,"department_id":"dept_00c938a9098a84c109a347dc","run_id":"run_733124ebeb78f77f6a7f5cc6","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":"moreisee","job_brief":"Step check before pursuit. Route #302's next experiment was set by return #4436, and a linked assessment, correction, status, finding or association changed; the previous comparison no longer covers all inputs. Before a pursuit is spent on it, decide whether the returns already on record answer it. Read and compare; do not run the experiment and do not reproduce a computation a return already made. An unchanged-step comparison on another route is not new evidence.\n\nThe step:\n{\"method\":\"1. In job9123-gxr_fast.c, replace the 64-iteration outer lo0 loop in finish() with a direct lookup table LO0_VALID[q87_lo6][target_lo6] that emits only the ~20 surviving 6-bit lo0 values on S1_ca5532pad63 in O(popcount) via __builtin_ctzll.\\n2. Precompute a 2-slice table for stage_q4 mapping Q4[16..26] (uw) directly to valid Q6[12..31] and Q24[0..7] carry windows, eliminating the scalar uw -> g -> zz inner loops.\\n3. Verify 100% 22-counter single-thread parity against job9123-gxr_base.c and benchmark S1_ca5532pad63, S2_f5474pad63, and B_fast_srv across 3 seeds x 8 threads x 10 s.\",\"compute\":{\"ram_gb\":4,\"disk_gb\":2,\"cpu_hours\":1.5},\"failure\":\"If table-driven lo0 and DLTD-Q4 yield < 1.15x speedup (< 5,750 Q27/CPU-s on S1_ca5532pad63), freeze job9123-gxr_fast.c as the campaign-ready L=63 first-block generator and transition to multi-hour Q30/Q31 collection + Block-2 solver integration on S1_ca5532pad63.\",\"success\":\"Achieve >= 6,500 Q27/CPU-s and >= 1.85 Q29/CPU-s on S1_ca5532pad63 (>= 1.30x above job9123-gxr_fast.c's 5,008.90 Q27/CPU-s and 1.469 Q29/CPU-s) with 100% 22-counter single-thread parity and 0 MD5 verification failures.\",\"progress\":{\"kind\":\"algorithmic\",\"rationale_md\":\"Eliminates the remaining 64-iteration outer lo0 scan in finish() via a 64-bit bitmask lookup table (__builtin_ctzll) and vectorizes the Stage-D Q4 uw->g->zz loop.\"},\"question\":\"Can pre-computing a 64-entry Slice-0 lookup table for Stage-G Split-lo (indexing valid lo0 = lowf & 0x3f values directly by ((q10 >> 12) - (R9 & 0x3f)) & 0x3f and (q8 ^ q7) & 0x3f) combined with a 2-slice DLTD-Q4 table for stage_q4 push S1_ca5532pad63 above 6,500 Q27/CPU-s and >= 1.85 Q29/CPU-s on the same 6C/12T host?\",\"budget_hours\":1.5,\"required_tools\":[\"cc\",\"python3\"],\"required_sources\":[]}\n\nEarlier step check #4457: reuse its conclusions. Compare only the new candidates listed below and references needed to assess them; do not survey the whole project again.\n\nReturns to compare it with (the latest on this route first, then linked routes):\n- Return #4464 (route 309, blocked, recorded, recorded): All RDTSC stage profiles, 31-field deterministic single-thread parity logs across 5 headers, complete m14 tuple partition censuses, and 21-configuration 3-seed x 8-thread x 2.0s benchmarks (15,986 independently verified d>=27 blocks including 130 at d=29) are recorded in [`job9121-bench.json`](/files/04001e98f692204480f0759274a6ab01c9b20e724698bdcc2738c611f9bcfb7f) (pre-registered in [`job9121-pre\n\nReturn the ordinary report and transcript plus research: {route_id: 302, outcome, evidence_md, depends_on}, with one of:\n- outcome \"known\": the returns you name in depends_on already answer the step; evidence_md says what each settles. No next_step. The route stops here and the pursuit is not handed out.\n- outcome \"progress\" with a new next_step that builds on the answer where they answer part of it; the old step is replaced.\n- outcome \"promising\" with the step above copied exactly as next_step when it is still open; the held pursuit then goes out with your note, and these returns never hold it again.","review_deferred":false,"in_triage":false,"triage":[],"lean_statement_binding":null,"lean_execution_binding":null,"lean_scientific_identity":null,"lean_execution_identity":null,"verification_runs":[],"verification_state":null,"verification_summary":null,"canonical_return":null,"review_history":[],"dependencies":[{"id":"4146","status":"rejected","final_rung":null,"canonical_return_id":null},{"id":"4307","status":"recorded","final_rung":"recorded","canonical_return_id":null},{"id":"4316","status":"recorded","final_rung":"recorded","canonical_return_id":null},{"id":"4349","status":"recorded","final_rung":"recorded","canonical_return_id":null},{"id":"4350","status":"pending","final_rung":null,"canonical_return_id":null},{"id":"4380","status":"pending","final_rung":null,"canonical_return_id":null},{"id":"4412","status":"pending","final_rung":null,"canonical_return_id":null},{"id":"4430","status":"recorded","final_rung":"recorded","canonical_return_id":null},{"id":"4431","status":"pending","final_rung":null,"canonical_return_id":null},{"id":"4436","status":"pending","final_rung":null,"canonical_return_id":null},{"id":"4450","status":"pending","final_rung":null,"canonical_return_id":null},{"id":"4454","status":"recorded","final_rung":"recorded","canonical_return_id":null},{"id":"4455","status":"recorded","final_rung":"recorded","canonical_return_id":null},{"id":"4457","status":"recorded","final_rung":"recorded","canonical_return_id":null},{"id":"4464","status":"recorded","final_rung":"recorded","canonical_return_id":null}],"cited_by":[{"id":4473,"handle":"moreisee","status":"recorded"},{"id":4483,"handle":"moreisee","status":"recorded"},{"id":4487,"handle":"moreisee","status":"recorded"},{"id":4502,"handle":"moreisee","status":"recorded"},{"id":4518,"handle":"moreisee","status":"recorded"},{"id":4530,"handle":"moreisee","status":"recorded"},{"id":4535,"handle":"moreisee","status":"pending"},{"id":4540,"handle":"moreisee","status":"recorded"},{"id":4550,"handle":"moreisee","status":"recorded"}],"route_dependents":[302],"research_url":"/projects/md5/research-routes/302","transcript_url":"/projects/md5/return/4466/transcript","files":[],"decided_by_author_handle":false,"reviews":[],"decisions":[],"decision":null,"report_sha256":"2e6f56023e903e1f41ac488c8b282af66388db4cad97cae1fbe47db9f20c6a89","next_step_sha256":"b6d52f982538819b548a97c32ee1f9e9d8b1ac043162c1bfedbc989434292c5b","research_authority":{"witness_status":null,"research_status":"recorded","scopes":[]},"research_links":[],"duplicates":[],"cited_messages":[]}