SimdLinq

[!IMPORTANT] Cysharp/ZLinq, a new zero allocation LINQ library, includes LINQ to SIMD capabilities, it now contains all SimdLinq features. Please migrate to ZLinq.

SimdLinq

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

.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, LongSum, 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, Span, ReadOnlySpan, Memory, ReadOnlyMemory 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

Note that this library requires .NET 7 or above because this library uses static abstract members and the new cross platform .NET 7 SIMD Api.

using SimdLinq; // enable SimdLinq extension methods

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

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

To enable SimdLinq per file, add the using SimdLinq; using directive. To enable SimdLinq across the project, use global usings in the csproj file.

SimdLinqExtensions has methods for concrete data types, like int[] or Span, with the same names as LINQ's methods. If a method is eligible for SIMD optimization (such as the Sum of int[]), the SimdLinqExtensions method will be used for improved performance.

Unlike base LINQ, SimdLinq supports Span, allowing you to call methods such as Sum, Min, etc. on Span or ReadOnlySpan collections.

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

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

Compatibility

One of the reasons why LINQ's SIMD support in .NET 7 is incomplete, is compatibility. SimdLinq prioritises performance over some safety features and full compatibility with LINQ. Please note the following differences.

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 only support types that are 32-bit or higher(int, long, uint, ulong, double, float).

SimdLinq provides LongSum for int and uint, that returns long/ulong so avoid overflow.

float/double

Unlike LINQ, SimdLinq does not check for NaN in float/double Min/Max calculations. Additionally, the order of calculation for Sum is not sequential, leading to slight differences in floating-point operations compared to regular LINQ. For instance, LINQ returns 1.5710588F, while SimdLinq returns 1.5710589F. If compatibility is not a concern, this difference is not significant, but be aware of potential small tolerance differences.

Supported collections

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

Supported methods

• Sum for int, uint, long, ulong, float, double
• LongSum for int, uint
• 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.