## Problem Houses and boats (multis) were pathed correctly only by **delegation to the slow path**: `StepCache.TryGetMask` returns `Fallthrough_Multi` for any multi-covered cell, and `GetSuccessors` ran `CheckMovement` **8× per cell** (each re-resolving the tile stack via `GetStaticAndMultiTiles`) — a sustained per-step cost near every house/boat. There was also no automated test pinning multi pathfinding. This branch is the full multi-pathfinding effort in phases on one branch. ## Phase 1 — characterization tests (the oracle) Implementation-agnostic invariants: a cache-on≡cache-off whole-path invariant, a per-cell sweep vs `CheckMovement` over footprint+halo (incl. destination Z), hand-verified routing (around walls, demolish-reopens, foundation-redesign-honored), classic-house / foundation / boat fixtures, non-vacuity guards. These gate every later phase byte-for-byte. ## Phase 2 — live single-pass synthesizer `StepProbe.ComputeMultiMaskAt` synthesizes a covered cell's full 8-direction `StepMask` in one pass (the existing surface/step logic over `GetStaticAndMultiTiles` instead of 8× `CheckMovement`). `GetSuccessors` routes `Fallthrough_Multi` cells through it. No new cache, no `.swb` change. **~1.5×**, zero added allocations. ## Phase 3 / 3.1 — warm per-`multiID` interior cache (airtight) `MultiMaskCache` caches each fixed multi's local-frame `StepMask` for **interior** cells (cell + all 8 neighbours covered → terrain-neighbour-free → position-invariant), keyed by `multiID & 0x3FFF`, built lazily from the MCL. Interior cells become ~20 ns lookups. The cache is gated on a **per-instance footprint-clean flag** (`BaseMulti.PathInteriorCacheState`): an instance whose whole footprint terrain is below its floor (`maxTerrain < minFloor`) serves from the cache; a **dirty** instance (terrain intrudes — a contrived/GM placement) **degrades to live-synth, never a wrong mask**. This closes a cross-instance soundness gap (the cached mask depends on neighbour terrain too) found in a holistic review. The gate resets whenever the footprint's world-terrain relationship can change — **location, map, or ItemID** (a boat's heading swaps the MCL). **Boats are cached too.** Their per-`multiID` deck masks are movement-invariant (built once per heading), so a sailing boat never rebuilds them; only the cheap clean-flag rescan repeats per move (and only when pathed near). Narrow existing boats have little interior; wide galleons (`multi.mul`) would gain Castle-class. `HouseFoundation` (per-instance runtime `DesignState`) is the one type that stays on the live path. ## Verification - `UOContent.Tests` **454/454**, `Server.Tests` **708/708**, 0 failures. - The Phase-1 oracle (`MultiPathInvariantTests`, cache-on ≡ cache-off) stays **byte-identical** with the synthesizer + interior cache active. - Tests pin: footprint-cleanliness (clean vs sunk), dirty/cluttered placement degrades to live-synth while still pathing, clean placement serves, and the gate resets on move/ItemID change. ## Performance (modernuo/ModernUO-Benchmarks#8, full-fixture) Houses at **Green Acres** (flat staff region → clean footprints, the legit-placement case): | Route | Slow path | Phase 3.1 (interior cache) | Speedup | |-------|----------:|---------------------------:|--------:| | `around_a` (29 steps) | 238.3 µs | **49.1 µs** | **4.85×** | | `around_b` (29 steps) | 224.3 µs | **49.5 µs** | **4.53×** | ~130 of ~167 multi cells/route serve from the cache (~20 ns) vs 37 live-synth. Per-cell, the slow path's 8× `CheckMovement` grows with multi complexity (GuildHouse ~857 ns → Castle ~1,194 ns), the synthesizer is a flat ~780 ns, and the cache serve is ~20 ns — so big/tall multis (and wide galleons) gain most. Identical allocations throughout.
50 lines
1.7 KiB
C#
50 lines
1.7 KiB
C#
using Server.Engines.Pathing.Cache;
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using Server.PathAlgorithms;
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using Server.Systems.FeatureFlags;
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using Xunit;
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namespace Server.Tests.Pathfinding;
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[Collection("Sequential Pathfinding Tests")]
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public class MultiCacheUsedTests
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{
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private const int MapId = 1; // Trammel
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private const int GuildHouseId = 0x74;
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[Fact]
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public void PathNearMulti_IncrementsMultiLocalHits()
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{
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var map = Map.Maps[MapId];
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map.GetAverageZ(1480, 1620, out _, out var z, out _);
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var houseLoc = new Point3D(1480, 1620, (sbyte)z);
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var multi = new TestMulti(GuildHouseId);
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var cacheWas = ContentFeatureFlags.BitmapPathfindingCache;
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ContentFeatureFlags.BitmapPathfindingCache = true;
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var mover = MultiTestSupport.GetWalkerOracle(map, new Point3D(1480, 1630, (sbyte)z));
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try
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{
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multi.MoveToWorld(houseLoc, map);
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StepCache.Instance.Clear();
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var before = StepCache.Instance.GetStats().MultiLocalHits;
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// Start outside, goal on the far side, forcing expansion through the multi's halo.
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var start = new Point3D(1480, 1630, (sbyte)z);
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var goal = new Point3D(1480, 1610, (sbyte)z);
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var path = BitmapAStarAlgorithm.Instance.Find(mover, map, start, goal);
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var after = StepCache.Instance.GetStats().MultiLocalHits;
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Assert.NotNull(path);
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Assert.True(after > before, $"expected MultiLocalHits to increase, before={before} after={after}");
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}
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finally
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{
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mover.Delete();
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multi.Delete();
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ContentFeatureFlags.BitmapPathfindingCache = cacheWas;
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}
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}
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}
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