benchmark.txt

BenchmarkDotNet=v0.12.0, OS=Windows 10.0.17763.805 (1809/October2018Update/Redstone5), VM=VMware
Intel Core i7-7700K CPU 4.20GHz (Kaby Lake), 1 CPU, 4 logical and 4 physical cores
.NET Core SDK=2.1.507
  [Host]     : .NET Core 2.1.11 (CoreCLR 4.6.27617.04, CoreFX 4.6.27617.02), X64 RyuJIT
  DefaultJob : .NET Core 2.1.11 (CoreCLR 4.6.27617.04, CoreFX 4.6.27617.02), X64 RyuJIT


|         Method | Count |        Mean |     Error |    StdDev | Rank |
|--------------- |------ |------------:|----------:|----------:|-----:|
|       IntArray |  1000 |    407.0 ns |   5.17 ns |   4.84 ns |    1 |
|    StringArray |  1000 |  2,182.7 ns |  25.59 ns |  22.69 ns |    4 |
| StringBoxArray |  1000 |  1,673.0 ns |   9.62 ns |   8.53 ns |    2 |
|     StringSpan |  1000 |  1,940.8 ns |  21.95 ns |  20.53 ns |    3 |
|       IntArray | 10000 |  4,021.3 ns |  42.70 ns |  39.94 ns |    5 |
|    StringArray | 10000 | 22,162.3 ns | 883.03 ns | 867.25 ns |    8 |
| StringBoxArray | 10000 | 16,833.7 ns | 203.78 ns | 190.62 ns |    6 |
|     StringSpan | 10000 | 19,307.2 ns | 225.80 ns | 211.22 ns |    7 |

foo.cs

using System;

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

public struct StringBox {
  public string Value;
}

[RankColumn]
public class ArraysBenchmark {
  private int[] intArray;
  private string[] stringArray;
  private StringBox[] stringBoxArray;
  //private Memory<string> stringMemory;

  [Params(1000, 10000)]
  public int Count;

  [GlobalSetup]
  public void Setup() {
    intArray = new int[Count];
    stringArray = new string[Count];
    stringBoxArray = new StringBox[Count];
    //stringMemory = new Memory<string>();
  }

  [Benchmark]
  public void IntArray() {
    var array = intArray;
    for (var index = 0; index < array.Length; index++) {
      array[index] = 42;
    }
  }

  [Benchmark]
  public void StringArray() {
    var array = stringArray;
    for (var index = 0; index < array.Length; index++) {
      array[index] = "42";
    }
  }

  [Benchmark]
  public void StringBoxArray() {
    var array = stringBoxArray;
    for (var index = 0; index < array.Length; index++) {
      array[index].Value = "42";
    }
  }

  [Benchmark]
  public void StringSpan() {
    Span<string> span = stringArray;
    for (var index = 0; index < span.Length; index++) {
      span[index] = "42";
    }
  }
}

public class Program {
  public static void Main(string[] args) {
    BenchmarkRunner.Run<ArraysBenchmark>();
  }
}