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SimdLinq

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SimdLinq is a drop-in replacement of LINQ aggregation operations(Sum, Average, Min, Max) extremely faster with SIMD.

image

.NET 7 LINQ supports SIMD but it is very limited, due to compatibility and safety issues, it is only enabled for int[] Average, Min, Max and long[] Min, Max.

SimdLinq accelerates many methods (Sum, Average, Min, Max, MinMax, Contains, SequenceEqual) and types (byte, sbyte, short, ushort, int, uint, long, ulong, float, double). It can also be used with List<T>, Span<T>, ReadOnlySpan<T>, Memory<T>, ReadOnlyMemory<T> in addition to T[].

Using the overload resolution priority, all target methods are automatically SIMD by simply referencing the library and setting global using.

Quick Start

This library is distributed via NuGet.

PM> Install-Package SimdLinq

Currently supporting target framework is only .NET 7 or above because this library using static abstract members and .NET 7 SIMD API improvement.

using SimdLinq; // enable SimdLinq extension methods

var array = Enumerable.Range(1, 100000).ToArray();

var sum = array.Sum(); // used SimdLinqExtensions.Sum

To enable SimdLinq per file, uses using SimdLinq; namespace. To enable SimdLinq per project, uses global usings in csproj.

<ItemGroup>
    <Using Include="SimdLinq" />
</ItemGroup>

SimdLinqExtensions has methods for concrete types(int[], Span<double, etc...) that same name defined in LINQ, so that if a method is used that can effectively use SIMD (such as Sum of int[]), it will be executed.

Span<T> has no LINQ methods but SimdLinq has it so you can call Sum, Min etc in Span<T>/ReadOnlySpan<T>.

(double Min, double Max) GetMinMax(Span<double> span)
{
    return span.MinMax();
}

MinMax is a original extension of SimdLinq, that returns tuple of Min and Max.

Compatibility

One of the reasons why LINQ's SIMD support in .NET 7 is incomplete, is compatibility. SimdLinq top priority is SIMD enablement to fastest operation so sacrifices compatibility and some safety features. Please note the following.

Sum/Average

LINQ Sum is checked but SimdLinq is unchecked(SIMD operation is not supported overflow). To reduce the risk of overflow, Sum and Average supported types are 32-bit or higher(int, long, uint, ulong, double, float).

float/double

LINQ Min/Max of float/double checks NaN but SimdLinq does not. Also, the order in which Sum is calculated is not sequential. This results in floating-point operations that are different from those in regular LINQ. For example, with LINQ 1.5710588F but SIMD 1.5710589F. If compatibility is not important, this is not a problem, but be aware that very small tolerance can occur.

Supporting collection

T[], List<T>, Span<T>, ReadOnlySpan<T>, Memory<T>, ReadOnlyMemory<T>, Span<T>, ReadOnlySpan<T>.

Supporting methods

  • Sum for int, uint, long, ulong, float, double
  • Average for int, uint, long, ulong, float, double
  • Min for byte, sbyte, short, ushort, int, uint, long, ulong, float, double
  • Max for byte, sbyte, short, ushort, int, uint, long, ulong, float, double
  • MinMax for byte, sbyte, short, ushort, int, uint, long, ulong, float, double
  • Contains for byte, sbyte, short, ushort, int, uint, long, ulong, float, double
  • SequenceEqual for byte, sbyte, short, ushort, int, uint, long, ulong, float, double

SoA

SIMD with LINQ requires primitive array(or Span). Cysharp/StructureOfArraysGenerator makes easy to create SoA array to use SIMD easily.

License

This library is licensed under the MIT License.