fix(simulation): PR #198 review round — spillway split, courses disclosure, appendix fidelity
Tyre C2: DownstreamTarget::OpenSpillway added — success (open low ground, complete carved path) split from EdgeUnreachable (strict search exhaustion); both doc comments exact; test updated. Tyre C3: determinism docstring corrected (no BTreeMap; the endorheic f64 gate stated as deterministic-by- derivation). Hoshe H1: vacuous cliff_edge test replaced by single_basin_bowl_never_carves_a_gorge asserting the known-empty outcome. Hoshe H2/H3: courses-force-empty disclosure at rect_window_replica and in the results doc; courses.len() print added to the square production-fn bench — measured 3/6/10 courses in window (NOT courses-empty, verified twice); 'faithful stand-in' claim retracted for a precise scope statement; GJ1c 18-course run identified as the sole production-density rate. Tyre C1: appendix (4) headline rephrased — the tagged-envelope migration cannot be dodged by payload optimization (byte math), field-count-rule trigger is a workshop synthesis call; appendix (2) scope split per-shape. Hydrology unit suite 15/15; atlas lib suite 679 green; benches compile. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Claude Fable 5
@@ -223,9 +223,9 @@ necessary (workshops are not closed early on partial convergence).
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| # | Ticket | Headline result | Doc |
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|---|---|---|---|
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| ① | T-1177 | **Settled hydrology VIABLE**: 512×256 ~24 ms/body; all 273 bodies Rayon-parallel ~0.7–0.8 s; 8.3M cells ~5.7 s single-thread (no production path needs it synchronously). Cliff representation: dominant height + `channel_depth` + `cliff_edge` flag. Finding: gorge carving is structurally RARE (priority-flood finds true spill levels; zero carved cells at production scales — needs chained-basin geometry). Solver: priority-flood + Dijkstra overflow, pure function, determinism-proved. | [t1177](measurements/t1177-hydrology.md) |
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| ② | T-1178 | **Parallel throughput HOLDS at scale** (the T-1143 extrapolation gap, closed): ~190–220 ns/cell parallel flat from 330K→8.3M cells; 330K canvas ~64 ms, 2.07M ~0.4 s, 8.3M ~1.7–1.8 s (7.5–8.8× speedup); single-thread flat ~1.65 µs/cell, matches prior baseline within 8%. Cross-validated on three bodies incl. real courses. Measured through the real `build_district_window_layer`. | [t1178+t1154](measurements/t1178-t1154-derive-bench.md) |
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| ② | T-1178 | **Parallel throughput HOLDS at scale** (the T-1143 extrapolation gap, closed): ~190–220 ns/cell parallel flat from 330K→8.3M cells; 330K canvas ~64 ms, 2.07M ~0.4 s, 8.3M ~1.7–1.8 s (7.5–8.8× speedup); single-thread flat ~1.65 µs/cell, matches prior baseline within 8%. Throughput cross-validated on three bodies across two call paths (square real-`build_district_window_layer` = courses-light, 3–10 in window; rectangular replica loop = courses-empty by construction — agreeing within 0.3%); the courses-inclusive rate at real production density is measured once, GJ1c 330K with 18 courses at 195.0 ns/cell (within 2%, consistent with the <5% course-cost bound). | [t1178+t1154](measurements/t1178-t1154-derive-bench.md) |
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| ③ | T-1154 | **Block GO, Tile GO on cost** (~1.8–1.9 µs/cell, same band as District/Quarter). Octave cutoff buys ZERO below District spacing (verified: wavelength table bottoms at 128 m). Deepest-step realistic canvas (216×384 m @ 1 m = 83K cells): **~17 ms parallel — trivially interactive**. `voxel_relief` already in the Atlas path; `voxel_mosaic` untouched by it. Real gates are wire carrier + D-226(d) canvas policy, not cost. | [t1178+t1154](measurements/t1178-t1154-derive-bench.md) |
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| ④ | T-1179 | **PNG-per-field wins everywhere** — smallest AND fastest: 330K canvas = 638 KB (0.32× raw, 5.4/3.6 ms enc/dec) vs raw rmp 1.99 MB; RLE loses to raw (elev/temp near-noise per cell). **Tagged-envelope migration foreclosed as necessary**: best case is 21× the 30 KB ceiling at the SMALLEST size (563× at 8.3M). Corrected density: 6.00 B/cell measured raw. | [t1179](measurements/t1179-wire-table.md) |
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| ④ | T-1179 | **PNG-per-field wins everywhere** — smallest AND fastest: 330K canvas = 638 KB (0.32× raw, 5.4/3.6 ms enc/dec) vs raw rmp 1.99 MB; RLE loses to raw (elev/temp near-noise per cell). **No encoding brings a step canvas near the existing windowed-payload budget** (best case 21× the ~30 KB cap at the smallest size; 563× at 8.3M) — the tagged-envelope migration cannot be dodged by payload optimization. Whether the letter of the D-226 §2 *field-count* rule is what triggers it is a workshop synthesis call, not a measured result. Corrected density: 6.00 B/cell measured raw. | [t1179](measurements/t1179-wire-table.md) |
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| ⑤ | T-1180 | **Upload cost is a non-issue**: worst case (8.3M px RGBA8 create) ~3.2 ms median, ~2.4–2.9 ms frame-delta spike — never near the 16.6 ms budget. **L8 is 4–9× cheaper at every size** (~0.5–0.7 ms at 4K). Prefer `texture.update` reuse on step-cross; use L8 for single-channel planes. Windowed-only measurement (headless renderer fakes uploads). | [t1180](measurements/t1180-imagetexture.md) |
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Bench code (all `#[ignore]`d release tests): `server/src/atlas/hydrology_equilibrium.rs` + `server/tests/hydrology_equilibrium_bench.rs`, `server/tests/bmv_gridunit_bench.rs`, `server/tests/wire_encoding_bench.rs`.
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@@ -82,10 +82,26 @@ settled hydrology result out, same every time.
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basin's own spill level (0 for any step at or below it). Terminates at the
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first cell that is below sea level (`Sea`), belongs to a *different*
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already-resolved basin (`Basin(id)` — the chaining case), or is open low
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ground not otherwise claimed (`EdgeUnreachable`, the lake-fill analogue of
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`drainage::RIVER_DOWNSTREAM_EDGE_DRAIN`). Basins are processed in ascending
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spill-level order so a lower basin is always resolved before a higher one
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could chain into it.
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ground not otherwise claimed (`OpenSpillway` — a genuine SUCCESS terminus
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with a real, complete path, distinct from `EdgeUnreachable`, which is
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reserved strictly for search exhaustion — a review finding on PR #198
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caught an earlier draft conflating the two under one variant; see
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"`DownstreamTarget` outcome model" below). Basins are processed in
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ascending spill-level order so a lower basin is always resolved before a
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higher one could chain into it.
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**`DownstreamTarget` outcome model (four variants):**
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| Variant | Meaning | `outlet_path` |
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|---|---|---|
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| `Sea` | Reaches a sub-sea-level cell | real, complete |
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| `Basin(id)` | Chains into another already-resolved basin's footprint | real, complete |
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| `OpenSpillway` | Reaches open low ground — not sea, not another basin, but at/below the originating basin's own spill level | real, complete |
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| `EdgeUnreachable` | Search exhausted its budget without reaching ANY of the above (a genuine grid-topology dead end), OR no spill cell existed at all for the basin | best-effort partial (or empty) |
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Only `EdgeUnreachable` is a failure case; the other three (including
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`OpenSpillway`) are all successful overflow terminations that happen to
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land somewhere other than the sea or another lake.
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6. **Carving**: every path cell whose elevation exceeds the basin's spill
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level is cut down to it — `channel_depth_scaled[cell] = original[cell] -
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spill_level`, `cliff_edge[cell] = true` — but ONLY when the path's peak
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@@ -257,6 +273,16 @@ above-spill-level cells in sequence (not just a single-cell threshold); and
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the exact formula `solve()` uses to populate `channel_depth_scaled`/
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`cliff_edge` is arithmetically correct in isolation.
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The single-sealed-basin bowl fixture's own zero-carve result is asserted
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directly and non-vacuously by `single_basin_bowl_never_carves_a_gorge`
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(`cliff_edge.iter().all(|&c| !c)` + `channel_depth_scaled.iter().all(|&d| d
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== 0)`) — a PR #198 review finding (Hoshe H1) caught an earlier draft of
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this test (`cliff_edge_implies_positive_channel_depth`) asserting `if
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cliff_edge[i] { depth > 0 }` over that same fixture, which passes vacuously
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whenever (as here, always) the `if` never fires. The carving arithmetic
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itself stays covered by `carving_arithmetic_matches_original_minus_spill_level`,
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unchanged.
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**Practical read for the workshop:** at the working-grid resolutions this
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system actually runs at, gorge carving will be a **rare, not a routine**
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event — most basins settle by simple lake-fill, not canyon-cutting. The data
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@@ -122,7 +122,11 @@ target:
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1. **Square, through the real `build_district_window_layer` function**
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(nearest square side to the target cell count: 576²=331,776,
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1440²=2,073,600, 2880²=8,294,400 — landing exactly on 330K/2.07M/8.3M).
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1440²=2,073,600, 2880²=8,294,400 — landing exactly on 330K/2.07M/8.3M),
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with a **real `RiverNetwork` passed in** — this path runs the actual
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course-invention + riparian-cull machinery
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(`invent_courses_near_window`/`crop_courses_for_wire`) production runs,
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and is genuinely courses-inclusive (see the courses column below).
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2. **Real 16:9 rectangle** (768×432, 1920×1080, 3840×2160), via a
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hand-written row-chunked replica loop that mirrors
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`build_district_window_layer`'s internals cell-for-cell (same
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@@ -130,21 +134,19 @@ target:
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same per-cell output-field quantization `derive_window_cell` performs) —
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necessary because no production entry point derives a non-square window.
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Labelled **MEASURED (replica loop)** below to distinguish from **MEASURED
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(production fn)**.
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Both converge on the same rate at the same cell count (see table) — the
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replica loop is a faithful stand-in.
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(production fn)**. **This path is courses-EMPTY by construction** — see
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"Courses-inclusion disclosure (PR #198 review findings H2/H3)" below.
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### Headline table — District spacing, cutoff=2,048m (the shipped District band)
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| Canvas | Cells | Path | Parallel (16 threads) | ns/cell parallel | Single-thread | ns/cell single-thread | Speedup |
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|---|---:|---|---:|---:|---:|---:|---:|
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| 330K (square, side=576) | 331,776 | MEASURED (production fn) | 63.69 ms | 192.0 | 547.45 ms | 1,650.1 | 8.60× |
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| 330K (768×432) | 331,776 | MEASURED (replica loop) | 63.58 ms | 191.6 | 544.51 ms | 1,641.2 | 8.56× |
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| 2.07M (square, side=1440) | 2,073,600 | MEASURED (production fn) | 394.61 ms | 190.3 | 3,436.18 ms | 1,657.1 | 8.71× |
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| 2.07M (1920×1080) | 2,073,600 | MEASURED (replica loop) | 423.20 ms | 204.1 | 3,383.64 ms | 1,631.8 | 7.99× |
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| 8.3M (square, side=2880) | 8,294,400 | MEASURED (production fn) | 1,827.34 ms | 220.3 | 13,767.58 ms | 1,659.9 | 7.53× |
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| 8.3M (3840×2160) | 8,294,400 | MEASURED (replica loop) | 1,731.38 ms | 208.7 | 13,584.42 ms | 1,637.8 | 7.85× |
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| Canvas | Cells | Path | Courses in window | Parallel (16 threads) | ns/cell parallel | Single-thread | ns/cell single-thread | Speedup |
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|---|---:|---|---:|---:|---:|---:|---:|---:|
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| 330K (square, side=576) | 331,776 | MEASURED (production fn) | 3 | 63.69 ms | 192.0 | 547.45 ms | 1,650.1 | 8.60× |
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| 330K (768×432) | 331,776 | MEASURED (replica loop) | 0 (forced) | 63.58 ms | 191.6 | 544.51 ms | 1,641.2 | 8.56× |
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| 2.07M (square, side=1440) | 2,073,600 | MEASURED (production fn) | 6 | 394.61 ms | 190.3 | 3,436.18 ms | 1,657.1 | 8.71× |
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| 2.07M (1920×1080) | 2,073,600 | MEASURED (replica loop) | 0 (forced) | 423.20 ms | 204.1 | 3,383.64 ms | 1,631.8 | 7.99× |
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| 8.3M (square, side=2880) | 8,294,400 | MEASURED (production fn) | 10 | 1,827.34 ms | 220.3 | 13,767.58 ms | 1,659.9 | 7.53× |
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| 8.3M (3840×2160) | 8,294,400 | MEASURED (replica loop) | 0 (forced) | 1,731.38 ms | 208.7 | 13,584.42 ms | 1,637.8 | 7.85× |
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**All six rows MEASURED — none extrapolated.** Parallel per-cell rate is flat
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across every canvas size (190.3–220.3 ns/cell, the full spread is ~15% —
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@@ -154,6 +156,66 @@ the row-chunked `par_iter` throughput measured at 4,096 cells holds at 330K,
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2.07M, and 8.3M cells — no degradation from memory pressure, cache behavior,
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or Rayon chunking overhead at any tested size.**
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### Courses-inclusion disclosure (PR #198 review findings H2/H3)
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Hoshe's review found two related gaps in the original version of this
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document and the underlying bench, confirmed valid and fixed here:
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**H2 — the replica-loop path was undisclosed as courses-empty.**
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`rect_window_replica` (the function backing every rectangular-canvas row
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above, and the 83K deep-step bench below) always calls `derive_at_metres`
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with an empty `&[]` course slice — it has no `RiverNetwork` wiring at all.
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This was true of the original bench and was not stated anywhere in the code
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or this document. **Fixed:** both the bench's module doc and the
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`rect_window_replica` function doc now state this explicitly, and cite the
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measured cost this excludes: `zoom_ladder_bench.rs`'s own
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`bench_course_cost_on_vs_off` measured the courses-on-vs-off delta at
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District cap (n=64, real GJ1c geometry) as **+0.09–0.21 ms against a ~5 ms
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baseline (under 5%)** — small, but real, and every rectangular-canvas number
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in this document (the three 16:9 headline rows AND the 83K deep-step bench)
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excludes it.
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**H3 — the "square vs. rectangle converge" claim was unverified for courses,
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and the specific worry (both sides courses-empty) turned out not to be the
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case.** The original document claimed square and rectangle "converge... the
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replica loop is a faithful stand-in" without ever checking whether the
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square path (which DOES accept a real `RiverNetwork`) was actually deriving
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any courses at its measured window position — raising the possibility that
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the observed convergence was courses-empty vs courses-empty, which would
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prove nothing about courses cost. **Fix applied and run:** added a
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`layer.courses.len()` print to `bench_square_window_production_fn_district_spacing`,
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rebuilt, and ran it in isolation (release, `--ignored`, the three square
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cases only — no need to re-run the 8.3M single-thread or rectangular rows for
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this check). **Result: the square path is NOT courses-empty** — it measured
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`courses_in_window = 3, 6, 10` at 330K, 2.07M, 8.3M respectively (confirmed
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deterministic across two separate runs, identical counts both times). This
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happens because the synthetic gradient body's own drainage analysis produces
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river cells near the world origin (where the square benches centre their
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window), unlike GJ1c's real geometry which measured `courses_in_window=0` at
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the origin on a first attempt (see Cross-check 1 below, which corrects for
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exactly this by centring on a real river cell instead).
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**Corrected convergence statement (replaces the retracted "faithful stand-in"
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sentence):** the square production-fn path is courses-INCLUSIVE at light
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density (3–10 courses in a 331,776–8,294,400-cell window) and the
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rectangular replica-loop path is courses-EMPTY (always `&[]`, by
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construction) — so their agreement at 331,776 ≈ 576² (191.1–191.6 ns/cell,
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both paths, within 0.3% of each other) validates the **row-chunked loop
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mechanics** (chunking granularity, per-row dispatch overhead, per-cell derive
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cost) converging across two independently-written call sites at this course
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DENSITY — it does **not** demonstrate courses-inclusive and courses-empty
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rates are equivalent in general. The two paths differ in exactly one
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respect (courses present-but-sparse vs absent) and land within run-to-run
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noise of each other specifically because 3–10 courses out of 331,776+ cells
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is far too sparse a fraction to move the aggregate ns/cell figure outside
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the noise band — consistent with, not contradicting, the <5% per-cell
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course-cost delta `zoom_ladder_bench.rs` measured directly on a window with
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much higher course density. **The courses-inclusive rate at REAL production
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course density is covered only by Cross-check 1 below** (18 courses in a
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331,776-cell window, deliberately centred on real river geometry, not this
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document's sparse origin-centred windows) — cite that number, not the
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headline table, for a courses-representative rate.
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**Environment caveat (required):** these parallel per-cell rates (~190–220
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ns/cell) are **substantially faster** than the earlier-session baseline
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(1.785 µs/cell District cutoff at 4,096 cells, `atlas-zoom-ladder-t1143.md`
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@@ -169,7 +231,7 @@ differences between sessions), and parallel here is the genuinely new
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row-chunked-at-scale number the baseline table never measured. No
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apples-to-oranges claim is made anywhere in this table.
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### Cross-check 1 — real GJ1c body, real river network, courses genuinely exercised
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### Cross-check 1 — real GJ1c body, real river network, courses genuinely exercised at production-representative density
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| Canvas | Path | Wall time | ns/cell | courses_in_window |
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|---|---|---:|---:|---:|
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@@ -178,11 +240,16 @@ apples-to-oranges claim is made anywhere in this table.
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Window centred at district `(7520, -2932)` (converted from a real GJ1c river
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cell, `pixel_to_world_m`-equivalent formula, same technique
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`zoom_ladder_bench.rs`'s `bench_course_cost_on_vs_off` uses) — 18 real invented
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river courses fall inside the window, confirming this is not a courses-off
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measurement by accident. **195.0 ns/cell — within 2% of the synthetic
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fixture's 192.0 ns/cell at the identical shape.** The synthetic-gradient
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numbers in the headline table are not an artifact of a trivial body or an
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empty river network.
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river courses fall inside the window (nearly 2× the headline table's
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synthetic-body density at the same shape, 10 courses at 8.3M being the
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highest count that table reaches), confirming this is not a courses-off
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measurement by accident and giving the most production-representative course
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density measured in this document. **195.0 ns/cell — within 2% of the
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synthetic fixture's 192.0 ns/cell at the identical shape, and within the
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same noise band the headline table's own re-runs show.** This is the number
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to cite for "courses-inclusive, real geometry, real density" — the headline
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table's square rows are courses-inclusive but sparse (H3, above), and the
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rectangular rows are courses-empty entirely (H2, above).
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### Cross-check 2 — independent measurement, different body, same finding (T-1179)
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@@ -240,13 +307,14 @@ values no real window request can carry today, at the fixed 4,096-cell
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| Tile-adjacent (4 m), cutoff=4m | 7.75 ms | 1,892.2 | 1.892 |
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| Tile (1 m), cutoff=1m | 7.39 ms | 1,804.7 | 1.805 |
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**MEASURED**, re-run once for stability (second pass: 1,838.9 / N/A / N/A —
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Block re-run only, see below): all three land in the same band as the
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existing District (1.785 µs/cell) and Quarter (1.823 µs/cell) rows already in
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`atlas-zoom-ladder-t1143.md` §7 — **block and tile spacing cost the SAME
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per-cell rate as District/Quarter.** This is expected once the cutoff
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mechanism is understood (next section) — it is not a surprise finding, but it
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is a measured confirmation, not an assumption.
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**MEASURED, re-run once for stability** (first pass: 1,844.1 / 1,802.4 /
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1,798.5 ns/cell; second pass, shown in the table above: 1,838.9 / 1,892.2 /
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1,804.7 ns/cell — both passes agree within ~5%, no trend): all three land in
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the same band as the existing District (1.785 µs/cell) and Quarter
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(1.823 µs/cell) rows already in `atlas-zoom-ladder-t1143.md` §7 — **block and
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tile spacing cost the SAME per-cell rate as District/Quarter.** This is
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expected once the cutoff mechanism is understood (next section) — it is not a
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surprise finding, but it is a measured confirmation, not an assumption.
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### Why the cutoff buys nothing at Block/Tile spacing (verified, not assumed)
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@@ -338,6 +406,18 @@ comfortably inside any interactive-latency budget** — an order of magnitude
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below a single frame at even 30 fps (33ms), let alone a step-cross tolerance
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of a few hundred ms.
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**Courses disclosure (H2, applies here too):** this bench runs through
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`rect_window_replica`, the same courses-force-empty replica loop as the
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16:9 headline rows above — this 17ms figure **excludes** the per-cell
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riparian-test cost a real Tile-rung window with nearby river geometry would
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pay (measured elsewhere as +0.09–0.21ms against a ~5ms District-cap
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baseline, under 5%). At 82,944 cells the excluded cost would be smaller in
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absolute terms than that District-cap figure (far fewer cells, and course
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density at Tile spacing over a 216m×384m window is not yet measured at
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all), so this is very unlikely to change the "comfortably interactive"
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verdict — but it is an excluded cost, not a zero one, and is stated as such
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rather than left implicit.
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### Wire bytes at block/tile granularities (ARITHMETIC)
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**ARITHMETIC**, using `DistrictWindowLayer`'s own documented per-cell cost (7
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Reference in New Issue
Block a user