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Fix off-by-one error when registering components and add missing version bump #290

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Merged
genaray merged 2 commits into from
Oct 2, 2025
Merged

Fix off-by-one error when registering components and add missing version bump #290

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6ed8e63
Fix off-by-one error when registering components and add missing vers…
JoNax97 Aug 11, 2025
c7ebf69
Fix the SprseSet resizing logic and remove ad-hoc fix for edge indices.
JoNax97 Sep 5, 2025
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2 changes: 1 addition & 1 deletion src/Arch/Arch.csproj
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@

<PackageId>Arch</PackageId>
<Title>Arch</Title>
<Version>2.0.0</Version>
<Version>2.1.0</Version>
<Authors>genaray</Authors>
<PackageLicenseExpression>Apache-2.0</PackageLicenseExpression>
<Description>A high performance c# net.7 and net.8 archetype based ECS ( Entity component system ).</Description>
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7 changes: 3 additions & 4 deletions src/Arch/Buffer/SparseSet.cs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
using Arch.Core;
using Arch.Core.Utils;
using Arch.Core.Extensions.Internal;

namespace Arch.Buffer;

Expand Down Expand Up @@ -88,9 +88,8 @@ public void Add(int index)
if (index >= Capacity)
{
// Calculate new array size that fits the passed index
var amountOfMultiplications = (int)Math.Ceiling(Math.Log((index+1) / (float)Capacity, 2.0f));
var newLength = (int)Math.Pow(2, amountOfMultiplications) * Capacity;
newLength = Math.Max(Capacity, newLength+1);

@JoNax97 JoNax97 Sep 5, 2025

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This logic was failing when trying to grow from capacity = 0 to anything different than capacity = 1.

Because capacity was being used as a denominator it was causing a division by 0 and amountOfMultiplications was undeflowing. Then the multiplication by Capacity neutralized that and made it 0 again, and newLength+1 made it work only for the case where the desired capacity was 1.

var newCapacity = MathExtensions.NextPowerOfTwo(index + 1);

@JoNax97 JoNax97 Sep 5, 2025

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The new code uses bit shifting to find the next pow2 size without any floating point arithmetic.

var newLength = Math.Max(Capacity, newCapacity); // keep existing capacity if already larger

// Resize entities array
Array.Resize(ref Entities, newLength);
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5 changes: 2 additions & 3 deletions src/Arch/Core/ComponentRegistry.cs
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Expand Up @@ -126,10 +126,9 @@ private static ComponentType Add(Type type, int typeSize)
}

// Register and assign component id
var id = Size + 1;
meta = new ComponentType(id, typeSize);
meta = new ComponentType(Size, typeSize);
_typeToComponentType.Add(type, meta);
_types = _types.Add(id, type);
_types = _types.Add(Size, type);

Size++;
return meta;
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4 changes: 2 additions & 2 deletions src/Arch/Core/Edges/World.Edges.cs
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Expand Up @@ -16,7 +16,7 @@ public partial class World
private Archetype GetOrCreateArchetypeByAddEdge(in ComponentType type, Archetype oldArchetype)
{
Archetype archetype;
var edgeIndex = type.Id - 1;

@JoNax97 JoNax97 Sep 5, 2025

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These -1 were compensating for the off-by-one error on ComponentRegistry.

var edgeIndex = type.Id;

if (!oldArchetype.HasAddEdge(edgeIndex))
{
Expand All @@ -42,7 +42,7 @@ private Archetype GetOrCreateArchetypeByAddEdge(in ComponentType type, Archetype
private Archetype GetOrCreateArchetypeByRemoveEdge(in ComponentType type, Archetype oldArchetype)
{
Archetype archetype;
var edgeIndex = type.Id - 1;
var edgeIndex = type.Id;

if (!oldArchetype.HasRemoveEdge(edgeIndex))
{
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18 changes: 18 additions & 0 deletions src/Arch/Core/Extensions/Internal/MathExtensions.cs
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Expand Up @@ -17,4 +17,22 @@ public static int Max(int a, int b)
{
return a - ((a - b) & ((a - b) >> 31));
}


public static int NextPowerOfTwo(int x)
{
if (x <= 1)
{
return 1;
}

x--;
x |= x >> 1;
x |= x >> 2;
x |= x >> 4;
x |= x >> 8;
x |= x >> 16;
x++;
return x;
}
}
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