Reserve index 0 in SlotMap, improve unsafe collections

- Reserve index 0 as always invalid in SlotMap, ConcurrentSlotMap, UnsafeSlotMap, and UnsafeSparseSet; update all index checks and slot operations accordingly
- Refactor SlotMap to use parallel arrays and BitArray for occupancy
- Double capacity on resize for all major unsafe collections
- Add debugger display support for unsafe collections
- Improve NuGet publishing workflow to skip existing versions
- Increment package versions (LowLevel: 1.3.1, main: 1.0.2)
- Add comprehensive unit tests for SlotMap and ConcurrentSlotMap
- Update main program and documentation for new slot map behavior

.gitea/workflows/publish-nuget.yaml

@@ -22,29 +22,69 @@ jobs:
       - name: Restore dependencies
         run: dotnet restore
 
-      - name: Build all projects
+      # Note: We skipped the global "Build all projects" step.
-        run: dotnet build -c Release
+      # dotnet pack will build automatically, and we only want to build/pack 
+      # the specific projects that strictly need updates.
 
-      - name: Pack all projects
+      - name: Check and Pack Projects
+        env:
+          NUGET_API_KEY: ${{ secrets.NUGET_TOKEN }}
+          SOURCE_URL: "https://git.personalnas.com/api/packages/Misaki/nuget"
         run: |
+          mkdir -p ./artifacts
+          
           for projfile in $(find . -name "*.csproj"); do
-            if grep -q "<GeneratePackageOnBuild>True</GeneratePackageOnBuild>" "$projfile"; then
+            # 1. Check if the project is configured to generate a package
-              echo "Packing $projfile..."
+            GENERATE_PKG=$(dotnet build "$projfile" --getProperty:GeneratePackageOnBuild)
+            if [[ "$GENERATE_PKG" != "true" && "$GENERATE_PKG" != "True" ]]; then
+              continue
+            fi
+
+            # 2. Extract Package ID and Version efficiently
+            PACKAGE_ID=$(dotnet build "$projfile" --getProperty:PackageId)
+            VERSION=$(dotnet build "$projfile" --getProperty:Version)
+            
+            # Fallback: If PackageId is not explicitly set in csproj, use the filename
+            if [ -z "$PACKAGE_ID" ]; then
+              PACKAGE_ID=$(basename "$projfile" .csproj)
+            fi
+
+            echo "Checking $PACKAGE_ID version $VERSION..."
+
+            # 3. Check if version exists in Gitea Registry
+            # Convert ID to lowercase for URL consistency (NuGet V3 standard)
+            LOWER_ID=$(echo "$PACKAGE_ID" | tr '[:upper:]' '[:lower:]')
+            
+            # Gitea supports the NuGet V3 Registration endpoint
+            HTTP_CODE=$(curl -s -o /dev/null -w "%{http_code}" \
+              -H "Authorization: token $NUGET_API_KEY" \
+              "${SOURCE_URL}/registration/${LOWER_ID}/${VERSION}.json")
+
+            if [ "$HTTP_CODE" -eq 200 ]; then
+              echo "✅ Version $VERSION of $PACKAGE_ID already exists. Skipping..."
+            else
+              echo "🆕 Version $VERSION of $PACKAGE_ID is new. Building and Packing..."
+              
+              # Build and Pack only this project
               if ! dotnet pack "$projfile" -c Release -o ./artifacts; then
-                echo "Failed to pack $projfile"
+                 echo "❌ Failed to pack $projfile"
+                 exit 1
               fi
             fi
           done
 
-      - name: Publish all packages
+      - name: Publish new packages
         env:
           NUGET_API_KEY: ${{ secrets.NUGET_TOKEN }}
         run: |
-          for pkg in ./artifacts/*.nupkg; do
+          # If no packages were created (all skipped), exit gracefully
-            # Skip if no files exist (in case globs fail)
+          if [ ! -d "./artifacts" ] || [ -z "$(ls -A ./artifacts/*.nupkg 2>/dev/null)" ]; then
-            [ -e "$pkg" ] || continue
+            echo "No new packages to publish."
+            exit 0
+          fi
 
-            # Skip symbol packages if they exist
+          for pkg in ./artifacts/*.nupkg; do
+            # Skip symbol packages
             if [[ "$pkg" == *".symbols.nupkg" ]]; then
               continue
             fi

Misaki.HighPerformance.Jobs/JobScheduler.cs

@@ -9,6 +9,13 @@ namespace Misaki.HighPerformance.Jobs;
 public unsafe partial class JobScheduler
 {
     public static readonly TempJobAllocator* pTempAllocator;
+
+    /// <summary>
+    /// Gets the allocation handle for the temporary job allocator.
+    /// </summary>
+    /// <remarks>
+    /// You must dispose the allocation before the fourth time you call <see cref="TempJobAllocator.AdvanceFrame"/> after obtaining this handle.
+    /// </remarks>
     public static AllocationHandle TempAllocatorHandle => pTempAllocator->Handle;
 
     static JobScheduler()

Misaki.HighPerformance.LowLevel/Collections/UnsafeArray.cs

@@ -7,10 +7,38 @@ using System.Runtime.CompilerServices;
 
 namespace Misaki.HighPerformance.LowLevel.Collections;
 
+internal class UnsafeArrayDebugView<T>
+    where T : unmanaged
+{
+    private readonly UnsafeArray<T> _array;
+
+    public UnsafeArrayDebugView(UnsafeArray<T> array)
+    {
+        _array = array;
+    }
+
+    [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+    public T[] Items
+    {
+        get
+        {
+            var count = _array.Count;
+            var result = new T[count];
+            for (int i = 0; i < count; i++)
+            {
+                result[i] = _array[i];
+            }
+
+            return result;
+        }
+    }
+}
+
 /// <summary>
 /// A structure for managing an array of unmanaged types with unsafe memory operations.
 /// </summary>
 /// <typeparam name="T">Represents a type that can be stored in an unmanaged memory context.</typeparam>
+[DebuggerTypeProxy(typeof(UnsafeArrayDebugView<>))]
 public unsafe struct UnsafeArray<T> : IUnsafeCollection<T>
     where T : unmanaged
 {

Misaki.HighPerformance.LowLevel/Collections/UnsafeBitSet.cs

@@ -1,5 +1,6 @@
 using Misaki.HighPerformance.LowLevel.Buffer;
 using Misaki.HighPerformance.LowLevel.Utilities;
+using System.Diagnostics;
 using System.Numerics;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
@@ -7,6 +8,31 @@ using System.Text;
 
 namespace Misaki.HighPerformance.LowLevel.Collections;
 
+internal class UnsafeBitSetDebugView
+{
+    private readonly UnsafeBitSet _bitSet;
+    public UnsafeBitSetDebugView(UnsafeBitSet bitSet)
+    {
+        _bitSet = bitSet;
+    }
+
+    [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+    public bool[] Bits
+    {
+        get
+        {
+            var bits = new bool[_bitSet.Count];
+            for (var i = 0; i < bits.Length; i++)
+            {
+                bits[i] = _bitSet.IsSet(i);
+            }
+
+            return bits;
+        }
+    }
+}
+
+[DebuggerTypeProxy(typeof(UnsafeBitSetDebugView))]
 public unsafe struct UnsafeBitSet : IDisposable, IEquatable<UnsafeBitSet>
 {
     public ref struct Iterator
@@ -65,6 +91,9 @@ public unsafe struct UnsafeBitSet : IDisposable, IEquatable<UnsafeBitSet>
     /// <summary>
     /// Initializes a new instance of the <see cref="UnsafeBitSet" /> class.
     /// </summary>
+    /// <param name="minimalLength">The minimal length in bits.</param>
+    /// <param name="handle">The allocation handle.</param>
+    /// <param name="option">The allocation option.</param>
     public UnsafeBitSet(int minimalLength, AllocationHandle handle, AllocationOption option = AllocationOption.None)
     {
         var uints = (minimalLength >> _INDEX_SIZE) + int.Sign(minimalLength & _BIT_SIZE);

Misaki.HighPerformance.LowLevel/Collections/UnsafeList.cs

@@ -2,14 +2,40 @@ using Misaki.HighPerformance.LowLevel.Buffer;
 using Misaki.HighPerformance.LowLevel.Collections.Contracts;
 using Misaki.HighPerformance.LowLevel.Utilities;
 using System.Collections;
+using System.Diagnostics;
 using System.Runtime.CompilerServices;
 
 namespace Misaki.HighPerformance.LowLevel.Collections;
 
+internal class UnsafeListDebugView<T>
+    where T : unmanaged
+{
+    private readonly UnsafeList<T> _list;
+    public UnsafeListDebugView(UnsafeList<T> list)
+    {
+        _list = list;
+    }
+
+    [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+    public T[] Items
+    {
+        get
+        {
+            var array = new T[_list.Count];
+            for (int i = 0; i < _list.Count; i++)
+            {
+                array[i] = _list[i];
+            }
+            return array;
+        }
+    }
+}
+
 /// <summary>
 /// A collection that allows for unsafe operations on a list of unmanaged types.
 /// </summary>
 /// <typeparam name="T">Represents a type that can be stored in the collection, constrained to unmanaged types for performance and safety.</typeparam>
+[DebuggerTypeProxy(typeof(UnsafeListDebugView<>))]
 public unsafe struct UnsafeList<T> : IUnsafeCollection<T>
     where T : unmanaged
 {
@@ -210,7 +236,7 @@ public unsafe struct UnsafeList<T> : IUnsafeCollection<T>
     {
         if (_count >= Capacity)
         {
-            Resize(Capacity + (int)(Capacity * 0.5f));
+            Resize(Math.Max(1, Capacity * 2));
         }
 
         UnsafeUtility.WriteArrayElement(_array.GetUnsafePtr(), _count, value);

Misaki.HighPerformance.LowLevel/Collections/UnsafeQueue.cs

@@ -110,7 +110,7 @@ public unsafe struct UnsafeQueue<T> : IUnsafeCollection<T>
     {
         if (_count >= Capacity)
         {
-            Resize((int)(Capacity * 1.5f));
+            Resize(Math.Max(1, Capacity * 2));
         }
 
         UnsafeUtility.WriteArrayElement(_array.GetUnsafePtr(), (_offset + _count) % Capacity, value);

Misaki.HighPerformance.LowLevel/Collections/UnsafeSlotMap.cs

@@ -2,15 +2,43 @@ using Misaki.HighPerformance.LowLevel.Buffer;
 using Misaki.HighPerformance.LowLevel.Collections.Contracts;
 using Misaki.HighPerformance.LowLevel.Utilities;
 using System.Collections;
+using System.Diagnostics;
 using System.Runtime.CompilerServices;
 
 namespace Misaki.HighPerformance.LowLevel.Collections;
 
+internal class UnsafeSlotMapDebugView<T>
+    where T : unmanaged
+{
+    private readonly UnsafeSlotMap<T> _slotMap;
+    public UnsafeSlotMapDebugView(UnsafeSlotMap<T> slotMap)
+    {
+        _slotMap = slotMap;
+    }
+
+    [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+    public T[] Items
+    {
+        get
+        {
+            var items = new List<T>(_slotMap.Count);
+            var enumerator = _slotMap.GetEnumerator();
+            while (enumerator.MoveNext())
+            {
+                items.Add(enumerator.Current);
+            }
+
+            return items.ToArray();
+        }
+    }
+}
+
 /// <summary>
 /// Provides an unsafe, high-performance slot map for storing and managing unmanaged values, supporting fast insertion,
 /// removal, and lookup by slot index and generation.
 /// </summary>
 /// <typeparam name="T">The type of value to store in the slot map. Must be unmanaged.</typeparam>
+[DebuggerTypeProxy(typeof(UnsafeSlotMapDebugView<>))]
 public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
     where T : unmanaged
 {
@@ -53,7 +81,7 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
     private int _count;
     private int _capacity;
 
-    public readonly int Count => _count;
+    public readonly int Count => _count - 1;
     public readonly int Capacity => _capacity;
 
     public readonly bool IsCreated => _data.IsCreated && _generations.IsCreated && _freeSlots.IsCreated && _validBits.IsCreated;
@@ -88,7 +116,7 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
         _data = new UnsafeArray<T>(capacity, handle, allocationOption);
         _generations = new UnsafeArray<int>(capacity, handle, allocationOption);
         _freeSlots = new UnsafeQueue<int>(capacity, handle, allocationOption);
-        _validBits = new UnsafeBitSet(GetBitSetCapacity(capacity), handle, allocationOption);
+        _validBits = new UnsafeBitSet(capacity, handle, allocationOption);
 
         if (!allocationOption.HasFlag(AllocationOption.Clear))
         {
@@ -98,6 +126,9 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
 
         _count = 0;
         _capacity = capacity;
+
+        // Add a default item for invalid slot
+        Add(default, out _);
     }
 
     /// <summary>
@@ -112,12 +143,6 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
     {
     }
 
-    private static int GetBitSetCapacity(int capacity)
-    {
-        // Each uint32 can hold 32 bits.
-        return (capacity + 31) / 32;
-    }
-
     /// <summary>
     /// Adds the specified item to the collection and returns the index of the slot where it was stored.
     /// </summary>
@@ -128,7 +153,7 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
     {
         if (_count >= _capacity)
         {
-            Resize((int)(_capacity * 1.5f));
+            Resize(Math.Max(1, _capacity * 2));
         }
 
         int index;
@@ -185,9 +210,10 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
     /// <param name="slotIndex">The zero-based index of the slot to check. Must be greater than or equal to 0 and less than the current capacity.</param>
     /// <param name="generation">The generation value to compare against the slot's generation.</param>
     /// <returns>true if the slot at the specified index is valid and its generation matches the specified value; otherwise, false.</returns>
-    public bool Contains(int slotIndex, int generation)
+    public readonly bool Contains(int slotIndex, int generation)
     {
-        if (slotIndex < 0 || slotIndex >= Volatile.Read(ref _capacity))
+        // 0 is reserved for invalid slot
+        if (slotIndex <= 0 || slotIndex >= _capacity)
         {
             return false;
         }
@@ -211,13 +237,7 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
     /// <returns>true if the element at the specified slot index and generation is found; otherwise, false.</returns>
     public readonly bool TryGetElementAt(int slotIndex, int generation, out T value)
     {
-        if (slotIndex < 0 || slotIndex >= _capacity)
+        if (!Contains(slotIndex, generation))
-        {
-            value = default;
-            return false;
-        }
-
-        if (_generations[slotIndex] != generation)
         {
             value = default;
             return false;
@@ -237,14 +257,9 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
     /// <exception cref="InvalidOperationException">Thrown when the specified slot is not occupied or the generation does not match.</exception>
     public readonly T GetElementAt(int slotIndex, int generation)
     {
-        if (slotIndex < 0 || slotIndex >= _capacity)
+        if (!Contains(slotIndex, generation))
         {
-            throw new ArgumentOutOfRangeException(nameof(slotIndex), "Slot index is out of range.");
+            throw new InvalidOperationException("The specified slot is not occupied or the generation does not match.");
-        }
-
-        if (!_validBits.IsSet(slotIndex) || _generations[slotIndex] != generation)
-        {
-            throw new InvalidOperationException($"Slot {slotIndex} is not occupied.");
         }
 
         return _data[slotIndex];
@@ -260,15 +275,7 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
     /// <returns>A reference to the element of type <typeparamref name="T"/> at the specified slot and generation if it exists; otherwise, a null reference.</returns>
     public ref T GetElementReferenceAt(int slotIndex, int generation, out bool exist)
     {
-        if (slotIndex < 0 || slotIndex >= _capacity)
+        if (!Contains(slotIndex, generation))
-        {
-            exist = false;
-            return ref Unsafe.NullRef<T>();
-        }
-
-        ref var slot = ref _data[slotIndex];
-
-        if (!_validBits.IsSet(slotIndex) || _generations[slotIndex] != generation)
         {
             exist = false;
             return ref Unsafe.NullRef<T>();
@@ -283,7 +290,7 @@ public unsafe struct UnsafeSlotMap<T> : IUnsafeCollection<T>
         _data.Resize(newSize, option);
         _generations.Resize(newSize, option);
         _freeSlots.Resize(newSize, option);
-        _validBits.Resize(GetBitSetCapacity(newSize), option);
+        _validBits.Resize(newSize, option);
 
         _capacity = newSize;
     }

Misaki.HighPerformance.LowLevel/Collections/UnsafeSparseSet.cs

@@ -2,10 +2,37 @@ using Misaki.HighPerformance.LowLevel.Buffer;
 using Misaki.HighPerformance.LowLevel.Collections.Contracts;
 using Misaki.HighPerformance.LowLevel.Utilities;
 using System.Collections;
+using System.Diagnostics;
 using System.Runtime.CompilerServices;
 
 namespace Misaki.HighPerformance.LowLevel.Collections;
 
+internal class ConcurrentSparseSetDebugView<T>
+    where T : unmanaged
+{
+    private readonly UnsafeSparseSet<T> _set;
+    public ConcurrentSparseSetDebugView(UnsafeSparseSet<T> set)
+    {
+        _set = set;
+    }
+
+    [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+    public T[] Items
+    {
+        get
+        {
+            var items = new T[_set.Count];
+            var index = 0;
+            foreach (var item in _set)
+            {
+                items[index++] = item;
+            }
+
+            return items;
+        }
+    }
+}
+
 /// <summary>
 /// A sparse set data structure that provides O(1) insertion, deletion, and lookup operations.
 /// The sparse set uses three arrays: a dense array for storing values, a sparse array for mapping indices,
@@ -13,6 +40,7 @@ namespace Misaki.HighPerformance.LowLevel.Collections;
 /// Sparse indices work like entity IDs and are automatically generated.
 /// </summary>
 /// <typeparam name="T">Represents a type that can be stored in the sparse set, constrained to unmanaged types for performance and safety.</typeparam>
+[DebuggerTypeProxy(typeof(ConcurrentSparseSetDebugView<>))]
 public unsafe struct UnsafeSparseSet<T> : IUnsafeCollection<T>
     where T : unmanaged
 {
@@ -57,7 +85,7 @@ public unsafe struct UnsafeSparseSet<T> : IUnsafeCollection<T>
     private int _nextId; // Next available sparse index
     private int _capacity;
 
-    public readonly int Count => _count;
+    public readonly int Count => _count - 1;
     public readonly int Capacity => _capacity;
     public readonly bool IsCreated => _dense.IsCreated && _sparse.IsCreated && _reverse.IsCreated;
 
@@ -103,7 +131,10 @@ public unsafe struct UnsafeSparseSet<T> : IUnsafeCollection<T>
         _nextId = 0;
         _capacity = capacity;
 
-        Clear();
+        _sparse.AsSpan().Fill(-1);
+        _generations.Clear();
+
+        Add(default, out _); // Make index 0 invalid
     }
 
     /// <summary>
@@ -147,7 +178,7 @@ public unsafe struct UnsafeSparseSet<T> : IUnsafeCollection<T>
         // Resize dense arrays if necessary
         if (_count >= _capacity)
         {
-            Resize((int)(_capacity * 1.5f));
+            Resize(Math.Max(1, _capacity * 2));
         }
 
         // Add the value to the dense array and update mappings
@@ -209,7 +240,8 @@ public unsafe struct UnsafeSparseSet<T> : IUnsafeCollection<T>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public readonly bool Contains(int sparseIndex, int generation)
     {
-        if (sparseIndex < 0 || sparseIndex >= _sparse.Count)
+        // 0 is reserved as invalid index
+        if (sparseIndex <= 0 || sparseIndex >= _sparse.Count)
         {
             return false;
         }

Misaki.HighPerformance.LowLevel/Collections/UnsafeStack.cs

@@ -2,15 +2,43 @@ using Misaki.HighPerformance.LowLevel.Buffer;
 using Misaki.HighPerformance.LowLevel.Collections.Contracts;
 using Misaki.HighPerformance.LowLevel.Utilities;
 using System.Collections;
+using System.Diagnostics;
 using System.Runtime.CompilerServices;
 
 namespace Misaki.HighPerformance.LowLevel.Collections;
 
+internal class UnsafeStackDebugView<T>
+    where T : unmanaged
+{
+    private readonly UnsafeStack<T> _stack;
+    public UnsafeStackDebugView(UnsafeStack<T> stack)
+    {
+        _stack = stack;
+    }
+
+    [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+    public unsafe T[] Items
+    {
+        get
+        {
+            var items = new T[_stack.Count];
+            var pItems = (T*)_stack.GetUnsafePtr();
+            for (int i = 0; i < _stack.Count; i++)
+            {
+                items[i] = pItems[i];
+            }
+
+            return items;
+        }
+    }
+}
+
 /// <summary>
 /// Provides a high-performance, unsafe stack data structure for unmanaged types, supporting manual memory management
 /// and allocation control.
 /// </summary>
 /// <typeparam name="T">The type of elements stored in the stack. Must be an unmanaged type.</typeparam>
+[DebuggerTypeProxy(typeof(UnsafeStackDebugView<>))]
 public unsafe struct UnsafeStack<T> : IUnsafeCollection<T>
     where T : unmanaged
 {
@@ -96,7 +124,7 @@ public unsafe struct UnsafeStack<T> : IUnsafeCollection<T>
     {
         if (_count >= Capacity)
         {
-            Resize((int)(Capacity * 1.5f));
+            Resize(Math.Max(1, Capacity * 2));
         }
 
         UnsafeUtility.WriteArrayElement(_array.GetUnsafePtr(), _count, value);

Misaki.HighPerformance.LowLevel/Misaki.HighPerformance.LowLevel.csproj

@@ -6,7 +6,7 @@
     <Nullable>enable</Nullable>
     <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
     <Authors>Misaki</Authors>
-    <AssemblyVersion>1.3.0</AssemblyVersion>
+    <AssemblyVersion>1.3.1</AssemblyVersion>
     <Version>$(AssemblyVersion)</Version>
     <GeneratePackageOnBuild>True</GeneratePackageOnBuild>
     <PackageProjectUrl>https://git.personalnas.com/Misaki/Misaki.HighPerformance.git</PackageProjectUrl>

Misaki.HighPerformance.Test/Program.cs

@@ -22,17 +22,10 @@
 
 //BenchmarkDotNet.Running.BenchmarkRunner.Run<Misaki.HighPerformance.Test.Benchmark.CollectionBenchmark>();
 
+using Misaki.HighPerformance.Collections;
 using Misaki.HighPerformance.LowLevel.Buffer;
 using Misaki.HighPerformance.LowLevel.Collections;
 
-using var scope = AllocationManager.CreateStackScope();
+var csm = new ConcurrentSlotMap<int>();
-var array = new UnsafeArray<int>(10, scope.AllocationHandle);
+Console.WriteLine(csm.Contains(0, 0));
-for (var i = 0; i < array.Count; i++)
+Console.WriteLine(csm.Count == 0);
-{
-    array[i] = i;
-}
-
-foreach (var item in array.AsSpan())
-{
-    Console.WriteLine(item);
-}

Misaki.HighPerformance.Test/UnitTest/Collections/TestConcurrentSlotMap.cs

@@ -0,0 +1,60 @@
+using Misaki.HighPerformance.Collections;
+using System.Collections.Concurrent;
+
+namespace Misaki.HighPerformance.Test.UnitTest.Collections;
+
+[TestClass]
+public class TestSlotMap
+{
+    private SlotMap<int> _slotMap = null!;
+
+    [TestInitialize]
+    public void Initialize()
+    {
+        _slotMap = new SlotMap<int>();
+    }
+
+    [TestMethod]
+    public void TestDefaultIndex()
+    {
+        Assert.IsFalse(_slotMap.Contains(0, 0));
+    }
+
+    [TestMethod]
+    public void TestAddAndContains()
+    {
+        var slotIndex = _slotMap.Add(42, out var generation);
+        Assert.IsTrue(_slotMap.Contains(slotIndex, generation));
+        Assert.AreEqual(42, _slotMap.GetElementAt(slotIndex, generation));
+    }
+
+    [TestMethod]
+    public void TestRemove()
+    {
+        var slotIndex = _slotMap.Add(100, out var generation);
+        Assert.IsTrue(_slotMap.Contains(slotIndex, generation));
+        var removed = _slotMap.Remove(slotIndex, generation);
+        Assert.IsTrue(removed);
+        Assert.IsFalse(_slotMap.Contains(slotIndex, generation));
+    }
+
+    [TestMethod]
+    public void TestRemoveInvalid()
+    {
+        var slotIndex = _slotMap.Add(200, out var generation);
+        Assert.IsTrue(_slotMap.Contains(slotIndex, generation));
+        var removed = _slotMap.Remove(slotIndex, generation + 1); // Wrong generation
+        Assert.IsFalse(removed);
+        Assert.IsTrue(_slotMap.Contains(slotIndex, generation));
+    }
+
+    [TestMethod]
+    public void TestIndexReuse()
+    {
+        var slotIndex1 = _slotMap.Add(300, out var generation1);
+        _slotMap.Remove(slotIndex1, generation1);
+        var slotIndex2 = _slotMap.Add(400, out var generation2);
+        Assert.AreEqual(slotIndex1, slotIndex2);
+        Assert.AreNotEqual(generation1, generation2);
+    }
+}

Misaki.HighPerformance.Test/UnitTest/Collections/TestSlotMap.cs

@@ -0,0 +1,127 @@
+using Misaki.HighPerformance.Collections;
+using System.Collections.Concurrent;
+
+namespace Misaki.HighPerformance.Test.UnitTest.Collections;
+
+[TestClass]
+public class TestConcurrentSlotMap
+{
+    private ConcurrentSlotMap<int> _slotMap = null!;
+
+    public TestContext TestContext
+    {
+        get;
+        set;
+    }
+
+    [TestInitialize]
+    public void Initialize()
+    {
+        _slotMap = new ConcurrentSlotMap<int>();
+    }
+
+    [TestMethod]
+    public void TestDefaultIndex()
+    {
+        Assert.IsFalse(_slotMap.Contains(0, 0));
+    }
+
+    [TestMethod]
+    public void TestAddAndContains()
+    {
+        var slotIndex = _slotMap.Add(42, out var generation);
+        Assert.IsTrue(_slotMap.Contains(slotIndex, generation));
+        Assert.AreEqual(42, _slotMap.GetElementAt(slotIndex, generation));
+    }
+
+    [TestMethod]
+    public void TestRemove()
+    {
+        var slotIndex = _slotMap.Add(100, out var generation);
+        Assert.IsTrue(_slotMap.Contains(slotIndex, generation));
+        var removed = _slotMap.Remove(slotIndex, generation);
+        Assert.IsTrue(removed);
+        Assert.IsFalse(_slotMap.Contains(slotIndex, generation));
+    }
+
+    [TestMethod]
+    public void TestRemoveInvalid()
+    {
+        var slotIndex = _slotMap.Add(200, out var generation);
+        Assert.IsTrue(_slotMap.Contains(slotIndex, generation));
+        var removed = _slotMap.Remove(slotIndex, generation + 1); // Wrong generation
+        Assert.IsFalse(removed);
+        Assert.IsTrue(_slotMap.Contains(slotIndex, generation));
+    }
+
+    [TestMethod]
+    public void TestIndexReuse()
+    {
+        var slotIndex1 = _slotMap.Add(300, out var generation1);
+        _slotMap.Remove(slotIndex1, generation1);
+        var slotIndex2 = _slotMap.Add(400, out var generation2);
+        Assert.AreEqual(slotIndex1, slotIndex2);
+        Assert.AreNotEqual(generation1, generation2);
+    }
+
+    [TestMethod]
+    public void TestConcurrentAdditions()
+    {
+        const int threadCount = 8;
+        const int itemsPerThread = 1000;
+        var tasks = new List<Task>();
+
+        for (int t = 0; t < threadCount; t++)
+        {
+            tasks.Add(Task.Run(() =>
+            {
+                for (int i = 0; i < itemsPerThread; i++)
+                {
+                    _slotMap.Add(i, out _);
+                }
+            }, TestContext.CancellationTokenSource.Token));
+        }
+
+        Task.WaitAll(tasks, TestContext.CancellationTokenSource.Token);
+        Assert.AreEqual(threadCount * itemsPerThread, _slotMap.Count);
+    }
+
+    [TestMethod]
+    public void TestConcurrentRandomAddRemove()
+    {
+        const int threadCount = 8;
+        const int operationsPerThread = 1000;
+
+        var tasks = new List<Task>();
+        var rand = new Random();
+        var addedItems = new ConcurrentBag<(int slotIndex, int generation)>();
+
+        var count = 0;
+
+        for (int t = 0; t < threadCount; t++)
+        {
+            tasks.Add(Task.Run(() =>
+            {
+                for (int i = 0; i < operationsPerThread; i++)
+                {
+                    if (rand.NextDouble() < 0.5)
+                    {
+                        var slotIndex = _slotMap.Add(i, out var generation);
+                        addedItems.Add((slotIndex, generation));
+
+                        Interlocked.Increment(ref count);
+                    }
+                    else if (addedItems.TryTake(out var item))
+                    {
+                        _slotMap.Remove(item.slotIndex, item.generation);
+                        Interlocked.Decrement(ref count);
+                    }
+                }
+            }, TestContext.CancellationTokenSource.Token));
+        }
+
+        Task.WaitAll(tasks, TestContext.CancellationTokenSource.Token);
+
+        Assert.AreEqual(count, _slotMap.Count);
+    }
+}

Misaki.HighPerformance/Collections/ConcureentSlotMap.cs

@@ -59,7 +59,7 @@ public class ConcurrentSlotMap<T> : IEnumerable<T>
     // For lock-free resizing
     private int _isResizing;
 
-    public int Count => Volatile.Read(ref _count);
+    public int Count => Volatile.Read(ref _count) - 1;
     public int Capacity => Volatile.Read(ref _capacity);
 
     public IEnumerator<T> GetEnumerator() => new Enumerator(this);
@@ -75,6 +75,8 @@ public class ConcurrentSlotMap<T> : IEnumerable<T>
 
         _data = new SlotEntry[initialCapacity];
         _freeSlots = new();
+
+        Add(default!, out _);
     }
 
     [MethodImpl(MethodImplOptions.NoInlining)]
@@ -209,7 +211,7 @@ public class ConcurrentSlotMap<T> : IEnumerable<T>
 
     public bool Contains(int slotIndex, int generation)
     {
-        if (slotIndex < 0 || slotIndex >= Volatile.Read(ref _capacity))
+        if (slotIndex <= 0 || slotIndex >= Volatile.Read(ref _capacity))
         {
             return false;
         }
@@ -231,85 +233,48 @@ public class ConcurrentSlotMap<T> : IEnumerable<T>
     }
 
     public bool TryGetElement(int slotIndex, int generation, [MaybeNullWhen(false)] out T value)
+    {
+        if (!Contains(slotIndex, generation))
         {
             value = default;
-
-        if (slotIndex < 0 || slotIndex >= Volatile.Read(ref _capacity))
-        {
             return false;
         }
 
-        ref var slot = ref _data[slotIndex];
+        value = _data[slotIndex].value!;
-
-        // Read generation first, then validity, then value for consistency
-        var currentGeneration = Volatile.Read(ref slot.generation);
-        var isValid = Volatile.Read(ref slot.isValid) == 1;
-
-        if (isValid && currentGeneration == generation)
-        {
-            // Double-check that the slot is still valid with same generation
-            // to avoid race condition where slot gets removed between reads
-            if (Volatile.Read(ref slot.isValid) == 1 && Volatile.Read(ref slot.generation) == generation)
-            {
-                value = slot.value!;
         return true;
     }
-        }
-
-        return false;
-    }
 
     public T GetElementAt(int slotIndex, int generation)
     {
-        if (slotIndex < 0 || slotIndex >= Volatile.Read(ref _capacity))
+        if (!TryGetElement(slotIndex, generation, out var value))
-        {
-            throw new ArgumentOutOfRangeException(nameof(slotIndex), "Slot index is out of range.");
-        }
-
-        ref var slot = ref _data[slotIndex];
-
-        if (Volatile.Read(ref slot.isValid) == 0 || Volatile.Read(ref slot.generation) != generation)
         {
             throw new InvalidOperationException($"Slot {slotIndex} is not occupied or generation mismatch.");
         }
 
-        return slot.value!;
+        return value;
     }
 
     public ref T GetElementReferenceAt(int slotIndex, int generation, out bool exist)
     {
-        if (slotIndex < 0 || slotIndex >= Volatile.Read(ref _capacity))
+        if (!Contains(slotIndex, generation))
-        {
-            exist = false;
-            return ref Unsafe.NullRef<T>();
-        }
-
-        ref var slot = ref _data[slotIndex];
-
-        if (Volatile.Read(ref slot.isValid) == 0 || Volatile.Read(ref slot.generation) != generation)
         {
             exist = false;
             return ref Unsafe.NullRef<T>();
         }
 
         exist = true;
-        return ref slot.value!;
+        return ref _data[slotIndex].value!;
     }
 
-    public void UpdateElement(int slotIndex, int generation, T newValue)
+    public bool UpdateElement(int slotIndex, int generation, T newValue)
     {
-        if (slotIndex < 0 || slotIndex >= Volatile.Read(ref _capacity))
+        if (!Contains(slotIndex, generation))
         {
-            throw new ArgumentOutOfRangeException(nameof(slotIndex), "Slot index is out of range.");
+            return false;
         }
 
-        ref var slot = ref _data[slotIndex];
+        _data[slotIndex].value = newValue;
-        if (Volatile.Read(ref slot.isValid) == 0 || Volatile.Read(ref slot.generation) != generation)
+        return true;
-        {
-            throw new InvalidOperationException($"Slot {slotIndex} is not occupied or generation mismatch.");
-        }
-
-        slot.value = newValue;
     }
 
     public void Clear()
@@ -328,9 +293,6 @@ public class ConcurrentSlotMap<T> : IEnumerable<T>
             slot.value = default;
         }
 
-        // Clear free slots queue
+        _freeSlots.Clear();
-        while (_freeSlots.TryDequeue(out _))
-        {
-        }
     }
 }

Misaki.HighPerformance/Collections/SlotMap.cs

@@ -1,4 +1,4 @@
-using System.Collections;
+using System.Collections;
 using System.Diagnostics.CodeAnalysis;
 using System.Runtime.CompilerServices;
 
@@ -17,14 +17,14 @@ public class SlotMap<T> : IEnumerable<T>
             _currentIndex = -1;
         }
 
-        public readonly T Current => _slotMap._data[_currentIndex].value;
+        public readonly T Current => _slotMap._data[_currentIndex];
         readonly object? IEnumerator.Current => Current;
 
         public bool MoveNext()
         {
             while (++_currentIndex < _slotMap._capacity)
             {
-                if (_slotMap._data[_currentIndex].isValid)
+                if (_slotMap._isOccupiedBits[_currentIndex])
                 {
                     return true;
                 }
@@ -40,14 +40,9 @@ public class SlotMap<T> : IEnumerable<T>
         }
     }
 
-    private struct SlotData
+    private T[] _data;
-    {
+    private int[] _generations;
-        public T value;
+    private readonly BitArray _isOccupiedBits;
-        public int generation;
-        public bool isValid;
-    }
-
-    private SlotData[] _data;
     private readonly Queue<int> _freeSlots;
 
     private int _count;
@@ -64,8 +59,12 @@ public class SlotMap<T> : IEnumerable<T>
     {
         _capacity = initialCapacity;
 
-        _data = new SlotData[initialCapacity];
+        _data = new T[initialCapacity];
+        _generations = new int[initialCapacity];
+        _isOccupiedBits = new BitArray(initialCapacity);
         _freeSlots = new(initialCapacity);
+
+        Add(default!, out _);
     }
 
     private void Resize()
@@ -73,6 +72,9 @@ public class SlotMap<T> : IEnumerable<T>
         var newCapacity = _capacity * 2;
 
         Array.Resize(ref _data, newCapacity);
+        Array.Resize(ref _generations, newCapacity);
+
+        _isOccupiedBits.Length = newCapacity;
         _freeSlots.EnsureCapacity(newCapacity);
 
         _capacity = newCapacity;
@@ -95,31 +97,39 @@ public class SlotMap<T> : IEnumerable<T>
             slotIndex = _freeSlots.Dequeue();
         }
 
-        ref var slot = ref _data[slotIndex];
+        _data[slotIndex] = item;
-        slot.value = item;
+        _isOccupiedBits[slotIndex] = true;
-        slot.isValid = true;
-        generation = slot.generation;
 
         _count++;
 
+        generation = _generations[slotIndex];
         return slotIndex;
     }
 
+    public bool Contains(int slotIndex, int generation)
+    {
+        if (slotIndex <= 0 || slotIndex >= Volatile.Read(ref _capacity))
+        {
+            return false;
+        }
+
+        if (_isOccupiedBits[slotIndex] && _generations[slotIndex] == generation)
+        {
+            return true;
+        }
+
+        return false;
+    }
+
     public bool Remove(int slotIndex, int generation)
     {
-        if (slotIndex < 0 || slotIndex >= _capacity)
+        if (!Contains(slotIndex, generation))
         {
             return false;
         }
 
-        ref var slot = ref _data[slotIndex];
+        _generations[slotIndex]++;
-        if (slot.generation != generation)
+        _isOccupiedBits[slotIndex] = false;
-        {
-            return false;
-        }
-
-        slot.generation++;
-        slot.isValid = false;
 
         _freeSlots.Enqueue(slotIndex);
         _count--;
@@ -127,92 +137,49 @@ public class SlotMap<T> : IEnumerable<T>
         return true;
     }
 
-    public bool Contain(int slotIndex, int generation)
-    {
-        if (slotIndex < 0 || slotIndex >= Volatile.Read(ref _capacity))
-        {
-            return false;
-        }
-
-        ref var slot = ref _data[slotIndex];
-
-        if (slot.isValid && slot.generation == generation)
-        {
-            return true;
-        }
-
-        return false;
-    }
-
     public bool TryGetElement(int slotIndex, int generation, [MaybeNullWhen(false)] out T value)
     {
-        if (slotIndex < 0 || slotIndex >= _capacity)
+        if (!Contains(slotIndex, generation))
         {
             value = default;
             return false;
         }
 
-        ref var slot = ref _data[slotIndex];
+        value = _data[slotIndex];
-        if (slot.generation != generation)
-        {
-            value = default;
-            return false;
-        }
-
-        value = slot.value;
         return true;
     }
 
     public T GetElementAt(int slotIndex, int generation)
     {
-        if (slotIndex < 0 || slotIndex >= _capacity)
+        if (!Contains(slotIndex, generation))
         {
-            throw new ArgumentOutOfRangeException(nameof(slotIndex), "Slot index is out of range.");
+            throw new InvalidOperationException($"Slot {slotIndex} is not occupied or generation mismatch.");
         }
 
-        ref var slot = ref _data[slotIndex];
+        return _data[slotIndex];
-        if (!slot.isValid || slot.generation != generation)
-        {
-            throw new InvalidOperationException($"Slot {slotIndex} is not occupied.");
-        }
-
-        return slot.value;
     }
 
     public ref T GetElementReferenceAt(int slotIndex, int generation, out bool exist)
     {
-        if (slotIndex < 0 || slotIndex >= Volatile.Read(ref _capacity))
+        if (!Contains(slotIndex, generation))
-        {
-            exist = false;
-            return ref Unsafe.NullRef<T>();
-        }
-
-        ref var slot = ref _data[slotIndex];
-
-        if (!slot.isValid || slot.generation != generation)
         {
             exist = false;
             return ref Unsafe.NullRef<T>();
         }
 
         exist = true;
-        return ref slot.value!;
+        return ref _data[slotIndex];
     }
 
-    public void UpdateElement(int slotIndex, int generation, T newValue)
+    public bool UpdateElement(int slotIndex, int generation, T newValue)
     {
-        if (slotIndex < 0 || slotIndex >= Volatile.Read(ref _capacity))
+        if (!Contains(slotIndex, generation))
         {
-            throw new ArgumentOutOfRangeException(nameof(slotIndex), "Slot index is out of range.");
+            return false;
         }
 
-        ref var slot = ref _data[slotIndex];
+        _data[slotIndex] = newValue;
-        if (!slot.isValid || slot.generation != generation)
+        return true;
-        {
-            throw new InvalidOperationException($"Slot {slotIndex} is not occupied or generation mismatch.");
-        }
-
-        slot.value = newValue;
     }
 
     public void Clear()

Misaki.HighPerformance/Misaki.HighPerformance.csproj

@@ -6,7 +6,7 @@
     <Nullable>enable</Nullable>
 		<AllowUnsafeBlocks>True</AllowUnsafeBlocks>
     <Authors>Misaki</Authors>
-    <AssemblyVersion>1.0.1</AssemblyVersion>
+    <AssemblyVersion>1.0.2</AssemblyVersion>
     <Version>$(AssemblyVersion)</Version>
 		<GeneratePackageOnBuild>True</GeneratePackageOnBuild>
     <PackageProjectUrl>https://git.personalnas.com/Misaki/Misaki.HighPerformance.git</PackageProjectUrl>