Skip to content

CAT-SPEC.md

Latest commit

 

History

History
127 lines (82 loc) · 5.16 KB

CAT-SPEC.md

File metadata and controls

127 lines (82 loc) · 5.16 KB
Raw

Corridor Attention Table (CAT) v3 — Specification

The Corridor Attention Table (CAT) is per-square / per-wall-edge heat used for move ordering, LMR, and search move pruning. It is not used in static evaluation.

All values are centi-squares (integer). 100 cm ≈ one shortest-path step in eval units.

v3 vs v2 (why v3 exists)

CAT v2 CAT v3
Route model One backtracked shortest path per player All squares with corridor delta ≤ 3
Tunnel vision Wall on equal-length reroute missed if off witness path wall_edge_heat sees multi-route corridors
Build engine/src/cat/build.rs — add_player_corridor_attention same module, corridor delta formula

Witness shortest path is still used for fast gates (ordering, qsearch noisy check). CAT heat handles near-equal routes.

Corridor heat formula

Per player, per square sq:

delta(sq) = dist_from_pawn(sq) + dist_to_goal(sq) - shortest_to_goal
heat(sq)  = corridor_heat(delta) * pawn_path_weight(dist_from) / 100

corridor_heat(delta) — nonzero only if delta ≤ MAX_RELEVANT_CORRIDOR_DELTA (3):

corridor_heat(δ) = round( CAT_CORRIDOR_CM / (1 + δ × log2(δ+2)) ), min 1

CAT_CORRIDOR_CM = 200. Bottleneck bonus (+40 cm) when delta ≤ 2 and ≤1 forward continuation.

Both players accumulate into search CorridorAttention; web display uses per-player max (not sum) to avoid full-board flood.

Thresholds (engine/src/cat/constants.rs)

Constant Value Effect
CAT_CORRIDOR_CM 200 Per-player corridor ceiling
CAT_HOT_CM 160 Tactical — skip LMR; wall prune gate for multi-route
CAT_COLD_CM 60 Cold fringe — +1 LMR; UI warm tint from here
BOTTLENECK_BONUS_CM 40 Narrow corridor squares

UI display max = CAT_CORRIDOR_CM + BOTTLENECK_BONUS_CM = 240 cm.

Wall edge heat

For wall at (row, col, orientation):

edge_heat = max( heat(square_a), heat(square_b) ) per wall segment
wall_edge_heat = max(edge_top, edge_bottom) + min(edge_top, edge_bottom) / 4

Plus optional shape bonus (wall_shape_attention_bonus) for cross-gap geometry when local heat ≥ HOT — ordering only, does not un-prune dead walls.

Search integration

collect_search_moves (prune list)

Walls kept if wall_should_search:

  1. Not in dead zone (all touched squares unreachable)
  2. Cross-gap or blocks cross-gap → always search
  3. Touches gap play zone (mouth + ring)
  4. Probes sealed interior away from gap → skip
  5. Intersects opponent witness shortest path → search
  6. Else wall_edge_heat ≥ CAT_HOT_CM → search (multi-route)

Pawns: all legal (main search); qsearch pawns with our_path_gain > 0 only.

LMR / futility

  • move_corridor_attention(mv) = square or edge heat + shape bonus
  • ≥ CAT_HOT_CM → tactical (no reduction)
  • < CAT_COLD_CM → +1 reduction ply
  • Walls off witness path → non-tactical without BFS

Quiescence (noisy moves)

Chess captures → Quoridor path shocks:

  • Pawn: shortens our shortest path
  • Wall: increases opponent shortest path (witness gate + BFS confirm)
  • Quiet → stand pat; max 8 noisy moves; MAX_QDEPTH = 6

Gap / funnel positions (B-roll reference)

Vertical wall chain with single mouth at top:

  • Walls through V|gap|V → cross-gap → always search
  • Flank block beside gap → always search
  • Wall touching only sealed void away from gap mouth → prune

Bug fixed: neighbor loops in gap_play_zone_mask must use 0..=8, not 0..=9 (phantom edge mouths).

Implementation pointers

Symbol File
CorridorAttention engine/src/cat/attention.rs
build_corridor_attention engine/src/cat/build.rs
collect_search_moves, wall_should_search engine/src/cat/prune.rs
cat_snapshot_json engine/src/cat/viz.rs
Search consumer engine/legacy/search/alphabeta.rs
Web overlay web/src/lib/catHeatmap.js, boardView.js

Intuition (narration)

Quoridor has no captures. A move matters if it sits on any near-optimal route for either player. CAT v3 paints those corridors; the witness path is the express lane check; together they stop us pruning the wall that closes the last gap — or keeping ninety walls that touch cold fringe.