Misaki
d8a7b07624
- Refactor D3D12 backend and RenderGraph module - Update graphics RHI and core rendering components - Add Random.hlsl shader include - Regenerate API documentation and update user guides
157 lines
7.1 KiB
HTML
157 lines
7.1 KiB
HTML
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GhostEngine
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<article data-uid="">
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<h1 id="performance-and-memory">Performance and Memory</h1>
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<p>GhostEngine's ECS is explicitly designed around maximum CPU efficiency and AOT compatibility.</p>
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<h2 id="structure-of-arrays-soa">Structure of Arrays (SoA)</h2>
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<p>Traditional OOP patterns use Arrays of Structures (AoS), which causes cache misses when looping through objects to read a single field.</p>
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<p>GhostEngine ECS uses Structure of Arrays (SoA) at the chunk level. A 16KB unmanaged <code>Chunk</code> separates components into continuous blocks. When a <code>System</code> iterates a <code>ChunkView</code> and calls <code>GetComponentData<Position>()</code>, it receives a contiguous <code>Span<Position></code>.</p>
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<p>Because modern CPUs pre-fetch continuous memory aggressively, an ECS query can be up to orders of magnitude faster than naive OOP equivalents.</p>
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<h2 id="benchmark-example">Benchmark Example</h2>
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<p>The internal <code>Ghost.Entities.Test</code> benchmarks demonstrate the raw speed comparison:</p>
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<pre><code class="lang-csharp">// OOP Approach (~4000ns)
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for (var i = 0; i < _gameObjects.Length; i++)
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{
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_gameObjects[i].Position += new Vector4(_dt, _dt, _dt, 0);
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}
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// ECS Approach (~620ns)
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ref var query = ref _world.ComponentManager.GetEntityQueryReference(_queryIdentifier);
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foreach (var chunkView in query.GetChunkIterator())
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{
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var positions = chunkView.GetComponentDataRW<Position>();
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ref var address = ref MemoryMarshal.GetReference(positions);
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for (var i = 0; i < positions.Length; i++)
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{
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Unsafe.Add(ref address, i).value += new Vector4(_dt, _dt, _dt, 0);
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}
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}
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</code></pre>
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<p><strong>Results for 1,000,000 Entities:</strong></p>
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<ul>
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<li>Over <strong>98.5% cache hits</strong></li>
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<li>Approximately <strong>4x to 6x faster</strong> execution times</li>
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<li><strong>0 Bytes</strong> allocated per frame (Zero Garbage Collection)</li>
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</ul>
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<h2 id="versioning-and-change-tracking">Versioning and Change Tracking</h2>
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<p>Chunks maintain atomic version counters. Whenever <code>GetComponentDataRW<T>()</code> is called, the chunk updates its component version to match the current <code>World.Version</code>.</p>
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<p>Systems can rapidly bypass entire chunks without iterating them by checking <code>chunkView.HasChanged<T>(LastSystemVersion)</code>. This enables dirty-flag processing at near-zero cost.</p>
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<h2 id="unmanaged-constraints">Unmanaged Constraints</h2>
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<p>To guarantee this performance, the engine strictly enforces unmanaged types.</p>
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<ul>
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<li>You cannot put <code>string</code>, <code>class</code>, or managed arrays inside <code>IComponent</code>.</li>
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<li>For bulk temporary allocations during system updates, you should use <code>VirtualStack.Scope</code> or <code>AllocationManager</code> alongside <code>UnsafeList<T></code> to remain entirely off the .NET Garbage Collector heap.</li>
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</ul>
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