Avoid sort allocations #116109
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Avoid sort allocations #116109
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This was referenced May 30, 2025
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@EgorBot -intel using BenchmarkDotNet.Attributes;
public class Bench
{
int[] a = new int[10000];
Comparison<int> c = (int x, int y) => x - y;
[IterationSetup]
public void IterationSetup() { for (int i = 0; i < a.Length; i++) a[i] = i; }
[Benchmark]
public void Sort() => Array.Sort(a, c);
} |
jkotas
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area-System.Memory
tenet-performance
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Tagging subscribers to this area: @dotnet/area-system-memory |
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Could you please share perf numbers that demonstrate the performance improvements? The one micro-benchmark that I have kicked off above shows ~10% regression: EgorBot/runtime-utils#370 (comment) . |
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No, I haven't done any performance testing. |
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@2A5F You can use the benchmarks from the performance repo (we use them for ensuring there are no regressions): You can both trace files and disassembler output: https://github.com/dotnet/performance/tree/main/src/benchmarks/micro#quick-start |
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@adamsitnik Thanks for the notice Test Code[Benchmark]
public void Span_ComparerStruct() => _arrays[_iterationIndex++].AsSpan(0, Size).Sort(new ComparableComparerStruct());
private readonly struct ComparableComparerStruct : IComparer<T>
{
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public int Compare(T x, T y) => x.CompareTo(y);
}All test on Int32
BigStruct
IntClass
IntStruct
String
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Ideas and todo:
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To avoid duplicate code, could you do something like this: struct DelegateWrappedComparer<T> : IComparer<T>
{
private Comparer<T> _comparer;
public int Compare(T? x, T? y) => _comparer.Compare(x, y);
}And point the "old" version of the method to the new one, with this wrapper? Hope this is clear. |
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@andrewjsaid For Delegate is This test has expired/is invalid. I will retest the new code later when I have time. (benchmarks are really slow) |
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My reasoning was that by using the struct wrapper, methods like the below would be specialized for that struct and the JIT would be able to inline the call to private static void SwapIfGreater<TComparer>(Span<T> keys, TComparer comparer, int i, int j)
where TComparer : IComparer<T>, allows ref structHowever on further reflection I note that currently since |
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Oops already suggested 🤦 Thanks for the link |
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https://github.com/2A5F/dotnet-runtime/tree/try-uni-path Test results show that it is impossible to unify the path, therefore we should stick to only using the generic path on Int32
IntStruct
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note, the old impl branch: https://github.com/2A5F/dotnet-runtime/tree/avoid-sort-allocations-1 |
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Here are the benchmark results for the current pr branch Int32
IntStruct
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Modified
ArraySortHelperand addedArraySortHelper<T, TComparer>to allow generic struct TComparer without memory allocationSpan.Sort<T, TComparer>will not box now#39466
#39543