[upstream] Optimizations (erincatto/box2d#1050)

Improved performance, up to 20% gain in stacking scenarios.
Behavior change: contact solver bias stage no longer applies friction
(almost free perf gain)
Behavior change: b2World_Step still performs all operations, including
collision when timeStep == 0.
b2WorldDef now has b2Capacity that lets you pre-size some arrays to
reduce allocations.
Optimized hit events. These are basically free now.
Cleaned up and optimized solver scheduling.
Converted to new dynamic array type.
Added threading logic to prevent theoretical solver deadlock if the user
task system stalls worker 0.
Added Compounds benchmark.

Author: ikpil

src/Box2D.NET.Samples/Primitives/SampleEntry.cs

@@ -13,12 +13,14 @@ public class SampleEntry
     public readonly string Name;
     public readonly string Title;
     public readonly Func<SampleContext, Sample> CreateFcn;
+    public readonly Func<B2Capacity> CapacityFcn;
 
-    public SampleEntry(string category, string name, Func<SampleContext, Sample> createFcn)
+    public SampleEntry(string category, string name, Func<SampleContext, Sample> createFcn, Func<B2Capacity> capacityFcn = null)
     {
         Category = category;
         Name = name;
         Title = $"{Category} : {Name}";
         CreateFcn = createFcn;
+        CapacityFcn = capacityFcn;
     }
-}
+}

src/Box2D.NET.Samples/SampleContext.cs

@@ -41,6 +41,7 @@ public class SampleContext
 
     // These are persisted
     public int sampleIndex = 0;
+    public B2Capacity capacity;
 
 
     public B2DebugDraw debugDraw;

src/Box2D.NET.Samples/Samples/Benchmarks/BenchmarkCompound.cs

@@ -10,16 +10,16 @@
 
 namespace Box2D.NET.Samples.Samples.Benchmarks;
 
-public class BenchmarkCompound : Sample
+public class BenchmarkLargeCompounds : Sample
 {
-    private static readonly int SampleCompound = SampleFactory.Shared.RegisterSample("Benchmark", "Compound", Create);
+    private static readonly int SampleLargeCompounds = SampleFactory.Shared.RegisterSample("Benchmark", "Large Compounds", Create);
 
     private static Sample Create(SampleContext context)
     {
-        return new BenchmarkCompound(context);
+        return new BenchmarkLargeCompounds(context);
     }
 
-    public BenchmarkCompound(SampleContext context) : base(context)
+    public BenchmarkLargeCompounds(SampleContext context) : base(context)
     {
         if (m_context.restart == false)
         {
@@ -105,4 +105,4 @@ public BenchmarkCompound(SampleContext context) : base(context)
             }
         }
     }
-}
+}

src/Box2D.NET.Samples/Samples/Benchmarks/BenchmarkCompounds.cs

@@ -0,0 +1,29 @@
+// SPDX-FileCopyrightText: 2025 Erin Catto
+// SPDX-FileCopyrightText: 2025 Ikpil Choi(ikpil@naver.com)
+// SPDX-License-Identifier: MIT
+
+using static Box2D.NET.Shared.Benchmarks;
+
+namespace Box2D.NET.Samples.Samples.Benchmarks;
+
+public class BenchmarkCompounds : Sample
+{
+    private static readonly int SampleBenchmarkCompounds = SampleFactory.Shared.RegisterSample("Benchmark", "Compounds", Create);
+
+    private static Sample Create(SampleContext context)
+    {
+        return new BenchmarkCompounds(context);
+    }
+
+    public BenchmarkCompounds(SampleContext context) : base(context)
+    {
+        if (m_context.restart == false)
+        {
+            m_context.camera.center = new B2Vec2(0.0f, 50.0f);
+            m_context.camera.zoom = 25.0f * 2.2f;
+            m_context.enableSleep = false;
+        }
+
+        CreateCompounds(m_worldId);
+    }
+}

src/Box2D.NET.Samples/Samples/Benchmarks/BenchmarkManyPyramids.cs

@@ -8,13 +8,19 @@ namespace Box2D.NET.Samples.Samples.Benchmarks;
 
 public class BenchmarkManyPyramids : Sample
 {
-    private static readonly int SampleBenchmarkManyPyramids = SampleFactory.Shared.RegisterSample("Benchmark", "Many Pyramids", Create);
+    private static readonly int SampleBenchmarkManyPyramids =
+        SampleFactory.Shared.RegisterSampleWithCapacity("Benchmark", "Many Pyramids", Create, GetCapacity);
 
     private static Sample Create(SampleContext context)
     {
         return new BenchmarkManyPyramids(context);
     }
 
+    private static B2Capacity GetCapacity()
+    {
+        return GetManyPyramidsCapacity();
+    }
+
     public BenchmarkManyPyramids(SampleContext context) : base(context)
     {
         if (m_context.restart == false)

src/Box2D.NET.Samples/Samples/Benchmarks/BenchmarkWasher.cs

@@ -3,6 +3,7 @@
 // SPDX-License-Identifier: MIT
 
 using static Box2D.NET.Shared.Benchmarks;
+using static Box2D.NET.B2Worlds;
 
 namespace Box2D.NET.Samples.Samples.Benchmarks;
 
@@ -25,4 +26,12 @@ private BenchmarkWasher(SampleContext context) : base(context)
 
         CreateWasher(m_worldId);
     }
+
+    public override void Step()
+    {
+        base.Step();
+
+        B2ContactEvents events = b2World_GetContactEvents(m_worldId);
+        DrawTextLine($"hits = {events.hitCount}");
+    }
 }

src/Box2D.NET.Samples/Samples/Collisions/DynamicTree.cs

@@ -139,7 +139,7 @@ void BuildTree()
 
         float y = -4.0f;
 
-        m_tree = b2DynamicTree_Create();
+        m_tree = b2DynamicTree_Create(16);
 
         B2Vec2 aabbMargin = new B2Vec2(0.1f, 0.1f);