Table of Contents

Sample: IntroArgumentsSource

In case you want to use a lot of values, you should use [ArgumentsSource].

You can mark one or several fields or properties in your class by the [ArgumentsSource] attribute. In this attribute, you have to specify the name of public method/property which is going to provide the values (something that implements IEnumerable). The source may be instance or static. If the source is not in the same type as the benchmark, the type containing the source must be specified in the attribute constructor.

Source code

using System;
using System.Collections.Generic;
using System.Threading;
using BenchmarkDotNet.Attributes;

namespace BenchmarkDotNet.Samples
{
    public class IntroArgumentsSource
    {
        [Benchmark]
        [ArgumentsSource(nameof(Numbers))]
        public double ManyArguments(double x, double y) => Math.Pow(x, y);

        public IEnumerable<object[]> Numbers() // for multiple arguments it's an IEnumerable of array of objects (object[])
        {
            yield return new object[] { 1.0, 1.0 };
            yield return new object[] { 2.0, 2.0 };
            yield return new object[] { 4.0, 4.0 };
            yield return new object[] { 10.0, 10.0 };
        }

        [Benchmark]
        [ArgumentsSource(typeof(BenchmarkArguments), nameof(BenchmarkArguments.TimeSpans))] // when the arguments come from a different type, specify that type here
        public void SingleArgument(TimeSpan time) => Thread.Sleep(time);
    }

    public class BenchmarkArguments
    {
        public IEnumerable<object> TimeSpans() // for single argument it's an IEnumerable of objects (object)
        {
            yield return TimeSpan.FromMilliseconds(10);
            yield return TimeSpan.FromMilliseconds(100);
        }
    }
}

Output

| Method |  x |  y |      Mean |     Error |    StdDev |
|------- |--- |--- |----------:|----------:|----------:|
|    Pow |  1 |  1 |  9.360 ns | 0.0190 ns | 0.0149 ns |
|    Pow |  2 |  2 | 40.624 ns | 0.3413 ns | 0.3192 ns |
|    Pow |  4 |  4 | 40.537 ns | 0.0560 ns | 0.0524 ns |
|    Pow | 10 | 10 | 40.395 ns | 0.3274 ns | 0.3063 ns |

Another example

If the values are complex types you need to override ToString method to change the display names used in the results.

[DryJob]
public class WithNonPrimitiveArgumentsSource
{
    [Benchmark]
    [ArgumentsSource(nameof(NonPrimitive))]
    public void Simple(SomeClass someClass, SomeStruct someStruct)
    {
        for (int i = 0; i < someStruct.RangeEnd; i++)
            Console.WriteLine($"// array.Values[{i}] = {someClass.Values[i]}");
    }

    public IEnumerable<object[]> NonPrimitive()
    {
        yield return new object[] { new SomeClass(Enumerable.Range(0, 10).ToArray()), new SomeStruct(10) };
        yield return new object[] { new SomeClass(Enumerable.Range(0, 15).ToArray()), new SomeStruct(15) };
    }

    public class SomeClass
    {
        public SomeClass(int[] initialValues) => Values = initialValues.Select(val => val * 2).ToArray();

        public int[] Values { get; }

        public override string ToString() => $"{Values.Length} items";
    }

    public struct SomeStruct
    {
        public SomeStruct(int rangeEnd) => RangeEnd = rangeEnd;

        public int RangeEnd { get; }

        public override string ToString() => $"{RangeEnd}";
    }
}

| Method | someClass | someStruct |     Mean | Error |
|------- |---------- |----------- |---------:|------:|
| Simple |  10 items |         10 | 887.2 us |    NA |
| Simple |  15 items |         15 | 963.1 us |    NA |