VoxelForge/Standalone/Research/WorldAssemblerM3/Linux77/REPORT.md

Linux77 — FI/TN whole-view cost

Run and method

Final profile runs were FI/TN r12 and r13, source stamp 6532cc3d9ca7137b1b62a3ae1c7bc54ebffc8fa3d58a9f12740c11d2048f4a0d. They used eight workers, LOD0–8, hash=off, force_generate=off, and no --stream-hash; whole-tile skips remained active (481 FI, 578 TN). The route and phase tags are enabled only in the L77 build plus --linux77-profile. A separate default build with the profiler compiled out emitted zero samples.

The sampler used a per-thread CPU timer on each worker and the main thread. It recorded one PC per timer delivery and expanded delayed signals by 1 + si_overrun. Across four profiles it recorded 32,235 events / 128,923 weighted ticks, with nine timers per process, zero ring loss, and 129.06 s of profiled thread CPU. Handler CPU was 23.9 ms total (0.018%); per-run cost was 0.017–0.020%. The handler figure excludes kernel signal-delivery cost. The full per-call tag/counter overhead could not be isolated from run-to-run timing variation.

Cold readiness

Times are from the two final profiled runs; values show mean (range). LOD readiness means every desired tile at that LOD completed.

Ready point	FI	TN
First tile	0.377 s (0.376–0.377)	0.399 s (0.388–0.409)
27-tile neighborhood	0.744 s (0.714–0.774)	0.563 s (0.559–0.566)
LOD0	4.139 s (4.118–4.160)	4.046 s (3.921–4.172)
LOD1	4.618 s (4.593–4.642)	4.233 s (4.106–4.361)
LOD2	2.226 s (2.209–2.242)	2.040 s (1.983–2.096)
LOD0–2 all ready	4.618 s (4.593–4.642)	4.234 s (4.106–4.361)
Whole view ready	4.617 s (4.593–4.641)	4.233 s (4.105–4.360)

LOD1 is last, so LOD0–2 completion and whole-view readiness coincide in these runs. The ~1 s target is met for the first tile and neighborhood, but not for complete LOD0–2. The compiled-out controls measured 4.54–5.55 s FI and 4.70–4.74 s TN for whole-view readiness; they emitted no sampler records. Their timing scatter is too large to infer a small instrumentation delta. This headless run measures readiness, not frame-time stutter.

Exclusive cost account

Worker CPU is the sum of tile-worker time, averaged over r12/r13. Each cell is seconds (% of that scope); rounded values may not sum exactly. The phase split assigns field and composition work wherever it runs. MC, skirt, and refine columns contain the remaining non-field work in those caller stages, so composition inside a mesher call is not counted twice. Other is unclassified grid work plus the residual tile work.

Strate / scope	Worker CPU	Base packed / analytic / other	Graph	Bands	Passages	Support	Caps + edits	Dispatch	MC	Skirts	Refine	Other
FI LOD0–2	23.02 s	0.45 (1.9%) / 0.29 (1.3%) / 0.00	0.03 (0.1%)	0.52 (2.3%)	15.17 (65.9%)	3.26 (14.2%)	0.06 (0.3%)	0.84 (3.7%)	0.36 (1.6%)	0.02 (0.1%)	1.73 (7.5%)	0.30 (1.3%)
FI whole view	33.87 s	0.45 (1.3%) / 1.29 (3.8%) / 0.08 (0.2%)	0.04 (0.1%)	0.66 (2.0%)	18.16 (53.6%)	3.50 (10.3%)	0.09 (0.3%)	2.27 (6.7%)	0.47 (1.4%)	0.05 (0.2%)	6.35 (18.8%)	0.47 (1.4%)
TN LOD0–2	21.50 s	0.31 (1.4%) / 0.41 (1.9%) / 0.00	0.02 (0.1%)	0.57 (2.6%)	14.07 (65.4%)	2.90 (13.5%)	0.05 (0.2%)	0.78 (3.6%)	0.26 (1.2%)	0.04 (0.2%)	1.85 (8.6%)	0.25 (1.2%)
TN whole view	30.63 s	0.31 (1.0%) / 1.39 (4.5%) / 0.04 (0.1%)	0.04 (0.1%)	0.70 (2.3%)	15.91 (52.0%)	3.06 (10.0%)	0.06 (0.2%)	2.10 (6.8%)	0.38 (1.2%)	0.07 (0.2%)	6.21 (20.3%)	0.38 (1.2%)

“Base other” is native plus any other base route. Native appears at LOD4–8 in the whole view; legacy-surface and shared-source routes recorded no calls here. Analytic-batch also recorded no calls.

Route census and halo work

route-census.csv has exact route calls and points, plus expanded CPU time, for every LOD × caller-stage × route and the LOD0–2 / whole-view aggregates. Grid-fill points for LOD0–2 were:

Strate	Packed scalar	Packed X8 calls / points	Analytic scalar	Total grid points
FI	10.519 M	1.044 M / 6.319 M	0.989 M	17.827 M
TN	6.639 M	1.398 M / 8.423 M	1.548 M	16.610 M

Route-census time is exclusive by outer route and stage; composition time remains inside its packed/analytic route. The cost table is a separate, exclusive phase-first view of those same samples. dispatch_lookup and unknown rows have zero density-call counts by design.

Halo counts are exact; halo CPU is its sampled share of grid fill and overlaps the cost categories above. FI LOD0–2: 1.534 M of 17.827 M points (8.6%), about 1.92 s CPU (8.4%). FI whole view: 2.524 M of 24.439 M (10.3%), about 2.65 s (7.8%). TN LOD0–2: 1.485 M of 16.610 M (8.9%), about 1.89 s (8.8%). TN whole view: 2.382 M of 22.604 M (10.5%), about 2.47 s (8.1%). The run recorded halo points, not a set of coordinates, so exact cross-tile duplicate-coordinate counts are unavailable.

Closure and sampled hotspots

The grid estimate uses each LOD’s weighted grid_fill sample share of direct worker time; the comparison is direct mc_grid_ms timing:

Strate / scope	Sample estimate	Direct grid fill	Closure
FI LOD0–2	19.051 s	19.058 s	99.96%
FI whole view	23.931 s	23.903 s	100.11%
TN LOD0–2	17.365 s	17.377 s	99.93%
TN whole view	20.818 s	20.848 s	99.86%

Every LOD0–2 bin closed within 1.4%. Sparse far bins were noisier (FI LOD7 reached +18%; TN LOD6 reached −17%), while the whole-view totals still closed within 0.15%. Those per-LOD tails are sample variance, not missing work in the target scopes.

Top symbolized PC samples below are expanded-tick shares, grouped by addr2line leaf symbol; the lower_bound caller resolves into passage spatial-node visitation:

Sampled function	FI LOD0–2 / whole	TN LOD0–2 / whole
VF_FieldValueNoise	16.6% / 12.8%	17.0% / 12.9%
std::lower_bound in VisitNearestPassageSpatialNode	14.2% / 11.4%	11.5% / 9.2%
ApplyResolvedStratePassageCarves	6.5% / 5.6%	6.9% / 5.9%
VF_FieldLerp	6.3% / 4.8%	6.5% / 4.8%

Biggest lever

Passage carving is the largest phase: 65–66% of LOD0–2 CPU and 52–54% of whole-view CPU. A same-world 2× speedup in this phase would save about 7.0–7.6 worker CPU seconds for LOD0–2 and 8.0–9.1 seconds for the whole view: roughly one third of early CPU and one quarter of whole-view CPU. Removing the phase entirely is the measured hard ceiling (52–54% whole view); it is not a realistic target.

Failed or excluded runs

The first ITIMER_PROF attempts (fi-profile-r1, tn-profile-r1) recorded 1,822 and 1,701 samples, all on the main thread (lod=255), and are excluded. All final r12/r13 profiles and compiled-out controls exited successfully; none timed out.

No --stream-hash run was made, as required to keep skip behavior. The source diff adds only opt-in profiling tags, counters, and the sampler; generator and meshing formulas were not changed. Hash equality to 90378a5 was therefore not directly measured.