ModernUO/Projects/UOContent.Tests/Tests/Engines/Pathing/Multi/MultiSplitRoutingTests.cs
Kamron Batman 1c2e114b21
feat(pathfinding): multi-aware mask synthesizer + warm interior cache for house/boat cells (#2479)
## 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.
2026-06-09 08:02:05 -07:00

90 lines
3.2 KiB
C#

using Server.Engines.Pathing.Cache;
using Server.Items;
using Xunit;
using Xunit.Abstractions;
namespace Server.Tests.Pathfinding;
[Collection("Sequential Pathfinding Tests")]
public class MultiSplitRoutingTests
{
private readonly ITestOutputHelper _output;
public MultiSplitRoutingTests(ITestOutputHelper output) => _output = output;
// Open plain on Trammel used by existing pathfinding tests; room for a 7x7 house.
private const int MapId = 1;
private const int PlaceX = 1500;
private const int PlaceY = 1600;
[Fact]
public void PlacedMulti_RoutesFootprintAndHalo_ToFallthroughMulti()
{
StepCache.Instance.Clear();
var map = Map.Maps[MapId];
Assert.NotNull(map);
map.GetAverageZ(PlaceX, PlaceY, out _, out var z, out _);
var multi = new TestMulti(0x74); // GuildHouse footprint
multi.MoveToWorld(new Point3D(PlaceX, PlaceY, (sbyte)z), map);
try
{
var sector = map.GetRealSector(PlaceX >> 4, PlaceY >> 4);
Assert.True(sector.HasMultis, "placing a multi must set Sector.HasMultis");
var cells = MultiArt.FootprintWithHalo(multi);
var checkedCovered = 0;
foreach (var c in cells)
{
if (c.X < 0 || c.Y < 0 || c.X >= map.Width || c.Y >= map.Height)
{
continue;
}
var mask = StepCache.Instance.TryGetMask(map, c.X, c.Y, (sbyte)z);
Assert.Equal(CacheHitKind.Fallthrough_Multi, mask.HitKind);
checkedCovered++;
}
Assert.True(checkedCovered > 0, "non-vacuity: expected at least one covered cell");
_output.WriteLine($"covered/halo cells routed to fallthrough: {checkedCovered}");
}
finally
{
multi.Delete();
}
}
[Fact]
public void CleanMap_AfterMultiRemoved_ServesStaticHitAgain()
{
StepCache.Instance.Clear();
var prevThreshold = StepCache.Instance.MissPromotionThreshold;
StepCache.Instance.MissPromotionThreshold = 1; // build on first touch
var map = Map.Maps[MapId];
Assert.NotNull(map);
map.GetAverageZ(PlaceX, PlaceY, out _, out var z, out _);
var multi = new TestMulti(0x74);
multi.MoveToWorld(new Point3D(PlaceX, PlaceY, (sbyte)z), map);
var sector = map.GetRealSector(PlaceX >> 4, PlaceY >> 4);
Assert.True(sector.HasMultis, "placing a multi must set Sector.HasMultis");
try
{
multi.Delete();
Assert.False(sector.HasMultis, "removing the only multi must clear HasMultis");
// A cell that is NOT a static-fallthrough kind (e.g. off-map / multi) should now be
// eligible for a real static answer. Use the placement center, which is open plain.
var mask = StepCache.Instance.TryGetMask(map, PlaceX, PlaceY, (sbyte)z);
Assert.True(mask.IsHit, $"expected a real static answer after removal, got {mask.HitKind}");
_output.WriteLine($"post-removal hitKind at center: {mask.HitKind}");
}
finally
{
StepCache.Instance.MissPromotionThreshold = prevThreshold;
}
}
}