fix(simulation): PR #215 review fixes — hop-unit surcharge, D-210 amendment, citation + gap
The surcharge is now COASTAL_ACCESS_SURCHARGE_HOPS_PER_RING=1 added directly to length_cells (a pure hop count) — the old cost-unit constant div_ceil'd through MIN_CELL_COST silently produced 4 hops per ring, worst-case +24 (double the waypoint threshold) for physically short edges; worst case is now 6. A formula-pinning test asserts both the arithmetic and the constant. GJ251c's repro tightened to the documented 2 edges. The always-land citation now points at the real guarantee (features.rs::extract_attractors, D-209) — and checking the D-211 Phase-4 synthetic-overflow path exposed a real gap: it has no ocean-mask guard at all (T-1206 filed); documented, not papered over. D-210 gains a dated amendment recording the surrogate-anchor-at-cost carve-out and the relaxation-over-nudge adjudication. The bare 100 dependency dissolved with the unit fix. Edge counts on both repro bodies verified unchanged (reachability was never affected). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Claude Fable 5
+136
-37
@@ -84,30 +84,52 @@ const MIN_CELL_COST: u32 = RIVER_COST;
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/// T-1116 — coastal-cell routing relaxation. A settlement's OWN routing cell can
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/// be majority-water (`RouteGrid::build`'s `water_count * 2 > total_count` rule)
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/// even though the settlement's exact placement pixel is always land (D-211's
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/// attractor extraction filters `!ocean_mask`, D-209/attractor_matching.rs) —
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/// this is pure coastal-cell/downsample granularity (a routing cell spans up to
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/// `scale`² native pixels, ROUTE_W=64 on a 512-wide grid ⇒ up to 8² = 64 native
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/// cells folded into one routing cell). Without this, one water-majority routing
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/// cell under a coastal city hard-fails A* for every edge touching it (the
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/// documented T-1116 bug: GJ251c land 0.55 / GJ380c land 0.588 — land-majority
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/// BODIES with 0 routable edges).
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/// even though the settlement's exact placement pixel is (almost) always land:
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/// every REAL attractor type — including `PlainCenter` — is extracted with an
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/// explicit `!ta.ocean_mask[i]` guard (D-209, `features.rs::extract_attractors`,
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/// e.g. the `CoastalAccess` filter at line 544 and the `PlainCenter` filter at
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/// line 629). This is pure coastal-cell/downsample granularity (a routing cell
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/// spans up to `scale`² native pixels, ROUTE_W=64 on a 512-wide grid ⇒ up to
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/// 8² = 64 native cells folded into one routing cell). Without this relaxation,
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/// one water-majority routing cell under a coastal city hard-fails A* for every
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/// edge touching it (the documented T-1116 bug: GJ251c land 0.55 / GJ380c land
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/// 0.588 — land-majority BODIES with 0 routable edges).
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///
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/// **Known gap this relaxation also happens to cover, but does not fix at the
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/// source:** D-211's Phase-4 **synthetic overflow** path
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/// (`attractor_matching.rs::synthetic_attractor`, used when a body has more
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/// cities than real attractors) picks a position by pure grid arithmetic
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/// (`grid_h/2, grid_w/4` then a fixed spacing-walk) with **no terrain check at
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/// all** — it takes no heightmap/`TerrainAnalysis` argument and never reads
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/// `ocean_mask`. A synthetic-overflow settlement CAN land in open ocean. This
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/// routing relaxation still degrades that case gracefully (anchors to the
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/// nearest passable cell within `COASTAL_ANCHOR_MAX_RING`, or leaves it
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/// unrouted beyond that), but the placement itself is not guaranteed land —
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/// that gap belongs to D-211/Layer 3, not this file, and is reported rather
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/// than silently patched over here (flagged in PR #215 review, not yet ticketed).
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///
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/// The fix anchors routing to the NEAREST passable routing cell (ring-expansion
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/// search, deterministic tie-break) rather than the settlement's own impassable
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/// cell, and prices the gap as a short access-road surcharge
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/// (`COASTAL_ACCESS_COST_PER_RING` per ring) — a real quay/causeway link is
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/// modeled as more expensive than being fully inland, never free. This keeps
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/// `IMPASSABLE` an honest ocean/lake fact everywhere else in the cost field
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/// (D-210's terrain_modification_cost else-branch is untouched) — only the
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/// anchor LOOKUP for a start/goal settlement is relaxed, not open-ocean transit.
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/// (`COASTAL_ACCESS_SURCHARGE_HOPS_PER_RING` per ring) — a real quay/causeway
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/// link is modeled as more expensive than being fully inland, never free. This
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/// keeps `IMPASSABLE` an honest ocean/lake fact everywhere else in the cost
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/// field (D-210's terrain_modification_cost else-branch is untouched) — only
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/// the anchor LOOKUP for a start/goal settlement is relaxed, not open-ocean
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/// transit.
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const COASTAL_ANCHOR_MAX_RING: usize = 3;
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/// Surcharge added to a routed edge's cost per ring-cell of coastal anchor
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/// search (T-1116). One ring ≈ one `ORTHO` step at grassland baseline (100),
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/// so a ring-1 anchor costs the same as one extra plain grassland hop —
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/// noticeable in tie-breaks between near-identical routes, never prohibitive.
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const COASTAL_ACCESS_COST_PER_RING: u32 = ORTHO * 100;
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/// Surcharge added to a routed edge's reported `length_cells` per ring-cell of
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/// coastal anchor search (T-1116). `length_cells` is a pure HOP COUNT (the
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/// number of routing-cell steps in the path, [`RouteGrid::reconstruct`]), NOT
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/// a cost-unit quantity — so this constant is defined directly in hop units,
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/// not derived from `ORTHO`/cell-cost scale. One ring = one extra hop: a
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/// ring-1 anchor reports as if the path took one additional plain step,
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/// noticeable in tie-breaks between near-identical routes and in
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/// [`WAYPOINT_THRESHOLD_CELLS`], never prohibitive (worst case, both anchors
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/// at [`COASTAL_ANCHOR_MAX_RING`], is `2 * 3 = 6` extra hops — half the
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/// waypoint threshold, not double it).
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const COASTAL_ACCESS_SURCHARGE_HOPS_PER_RING: u32 = 1;
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/// A routed edge longer than this (in routing cells) earns a midpoint waypoint
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/// (tyre-round1.md: "edge length > ~12 regional cells").
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@@ -1145,23 +1167,25 @@ impl RouteGrid {
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/// T-1116: if `start`'s or `goal`'s own routing cell is water-majority
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/// (coastal-cell granularity — the settlement's exact pixel is always
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/// land, D-211/D-209), route to/from the nearest passable cell instead
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/// of hard-failing, and add a [`COASTAL_ACCESS_COST_PER_RING`] surcharge
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/// per ring of search distance to `length_cells` (an honest short
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/// access-road cost, not a free pass through water). Still returns `None`
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/// when no passable cell exists within [`COASTAL_ANCHOR_MAX_RING`] of
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/// either endpoint (fully water-locked at this granularity) or when no
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/// path connects the two anchors (genuinely separated by ocean).
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/// of hard-failing, and add [`COASTAL_ACCESS_SURCHARGE_HOPS_PER_RING`] hop
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/// to `length_cells` per ring of search distance (an honest short
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/// access-road cost, not a free pass through water — `length_cells` is a
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/// hop count, so the surcharge is expressed directly in hops, never
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/// converted through cost units). Still returns `None` when no passable
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/// cell exists within [`COASTAL_ANCHOR_MAX_RING`] of either endpoint
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/// (fully water-locked at this granularity) or when no path connects the
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/// two anchors (genuinely separated by ocean).
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fn astar(&self, start: (f64, f64), goal: (f64, f64)) -> Option<(Vec<(usize, usize)>, u32)> {
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let (sr0, sc0) = self.to_route_cell(start);
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let (gr0, gc0) = self.to_route_cell(goal);
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let (sr, sc, s_ring) = self.nearest_passable_cell(sr0, sc0)?;
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let (gr, gc, g_ring) = self.nearest_passable_cell(gr0, gc0)?;
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let surcharge =
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(s_ring as u32 + g_ring as u32).saturating_mul(COASTAL_ACCESS_COST_PER_RING);
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let surcharge_hops =
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(s_ring as u32 + g_ring as u32).saturating_mul(COASTAL_ACCESS_SURCHARGE_HOPS_PER_RING);
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let s = sr * self.rw + sc;
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let g = gr * self.rw + gc;
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if s == g {
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return Some((vec![(sr, sc)], surcharge.div_ceil(MIN_CELL_COST)));
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return Some((vec![(sr, sc)], surcharge_hops));
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}
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let n = self.rw * self.rh;
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@@ -1175,11 +1199,10 @@ impl RouteGrid {
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while let Some(Reverse((_, cur))) = open.pop() {
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if cur == g {
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let (path, length_cells) = self.reconstruct(&came, g);
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// Surcharge folded into the reported length (routing cells
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// are the shared unit `length_cells` already carries — see
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// WAYPOINT_THRESHOLD_CELLS/maintenance_authority callers).
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let surcharge_cells = surcharge.div_ceil(MIN_CELL_COST);
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return Some((path, length_cells.saturating_add(surcharge_cells)));
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// Surcharge folded into the reported length (already in hop
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// units — see WAYPOINT_THRESHOLD_CELLS/maintenance_authority
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// callers, which both read `length_cells` as a hop count).
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return Some((path, length_cells.saturating_add(surcharge_hops)));
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}
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let cr = cur / self.rw;
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let cc = cur % self.rw;
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@@ -2068,8 +2091,13 @@ mod tests {
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/// (`cascade.rs:405`), not a synthetic harness.
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#[test]
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fn real_body_coastal_settlements_produce_routable_edges() {
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// (body, expected node count, minimum edges after the fix).
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let cases = [("GJ251c", 3usize, 1usize), ("GJ380c", 3usize, 1usize)];
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// (body, expected node count, minimum edges after the fix). GJ251c's
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// documented post-fix count is 2 edges (all 3 placements land in
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// IMPASSABLE cells pre-fix); GJ380c's is 1 (2 of 3 placements are
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// already passable, only Sethvale needed the relaxation) — tightened
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// to the exact documented counts so a regression to fewer edges
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// fails loudly (PR #215 review finding 2).
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let cases = [("GJ251c", 3usize, 2usize), ("GJ380c", 3usize, 1usize)];
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for (body, min_placements, min_edges) in cases {
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let bws = crate::atlas::believability::cascade_for_body(42, body)
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.unwrap_or_else(|e| panic!("{body}: {e}"));
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@@ -2299,11 +2327,82 @@ mod tests {
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cell with no relaxation involved: got coastal={coastal_len} \
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surrogate={surrogate_len}"
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);
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let surcharge_cells = coastal_len - surrogate_len;
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let surcharge_hops = coastal_len - surrogate_len;
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assert!(
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surcharge_cells > 0,
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surcharge_hops > 0,
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"the coastal surcharge must be a strictly positive number of \
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routing-cell-equivalents, never zero (never free)"
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hops, never zero (never free)"
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);
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// PR #215 review finding 1: `length_cells` is a pure HOP COUNT, so the
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// surcharge must be expressed directly in hops — pin the exact value
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// (ring * COASTAL_ACCESS_SURCHARGE_HOPS_PER_RING) so a future unit
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// mismatch (e.g. reintroducing a cost-unit conversion) fails loudly
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// instead of merely "some positive number".
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assert_eq!(
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surcharge_hops,
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ring as u32 * COASTAL_ACCESS_SURCHARGE_HOPS_PER_RING,
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"the goal-side surcharge must be EXACTLY ring * hops-per-ring \
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(the start side contributes 0 here — start is ring 0)"
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);
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}
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/// PR #215 review finding 1 — pins the surcharge formula directly (no
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/// terrain, no A*, just the arithmetic in `astar`): the reported
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/// `length_cells` surcharge for a start/goal pair is EXACTLY
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/// `(start_ring + goal_ring) * COASTAL_ACCESS_SURCHARGE_HOPS_PER_RING`
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/// hops — never a cost-unit quantity in disguise. Uses the `s == g`
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/// short-circuit branch in `astar` (same routing cell for start and
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/// goal) to read the surcharge in complete isolation from pathfinding.
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#[test]
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fn coastal_surcharge_is_exactly_hops_per_ring_times_ring_count() {
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// Same 180-wide/scale-3 body as the other boundary tests: cell (0,3)
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// is IMPASSABLE (2-of-3 majority), cell (0,6) is passable (1-of-3,
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// stays land under the strict `>` rule).
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let w = 180u32;
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let h = 1u32;
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let mut hm = BodyHeightmap {
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body_id: "surcharge_formula_test".into(),
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width: w,
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height: h,
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data: vec![0.6; (w * h) as usize],
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sea_level: 0.3,
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};
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let idx = |r: u32, c: u32| (r * w + c) as usize;
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hm.data[idx(0, 9)] = 0.1;
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hm.data[idx(0, 10)] = 0.1;
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let dr = drainage::analyze(&hm.data, hm.width, hm.height, hm.sea_level);
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let ta = TerrainAnalysis::analyze(&hm, &dr);
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let grid = RouteGrid::build(&ta, &[], w, h);
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assert_eq!(
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grid.cost[3], IMPASSABLE,
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"sanity: cell (0,3) must be water-majority"
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);
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// Start AND goal both land in the same impassable cell (native cols
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// 9 and 11, both inside routing cell (0,3)) — astar's `s == g`
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// branch returns `surcharge_hops` directly with zero path-length
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// noise, isolating the formula from A*'s own hop accounting.
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let (_, ring) = {
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let (r, c, ring) = grid.nearest_passable_cell(0, 3).unwrap();
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((r, c), ring)
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};
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let (_, reported_hops) = grid
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.astar((0.0, 9.0), (0.0, 11.0))
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.expect("same-cell start/goal must resolve via the shared surrogate");
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assert_eq!(
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reported_hops,
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(ring as u32) * 2 * COASTAL_ACCESS_SURCHARGE_HOPS_PER_RING,
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"start and goal share the same impassable cell -> same ring on \
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both sides -> surcharge = 2 * ring * hops-per-ring, with ZERO \
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actual path hops (s == g after anchoring)"
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);
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// With the constant fixed at 1 hop/ring (finding 1's chosen value),
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// this resolves to a concrete number — pin it so a future change to
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// COASTAL_ACCESS_SURCHARGE_HOPS_PER_RING is a deliberate, visible act.
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assert_eq!(
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COASTAL_ACCESS_SURCHARGE_HOPS_PER_RING, 1,
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"if this changes, the assertion above must be re-derived, not \
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just relaxed"
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);
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}
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}
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