udlose/SpanIndexOfBenchmark.cs

## SpanIndexOfBenchmark.cs


// run with:
//  dotnet run -c Release --framework net10.0 -- --filter *


// * Summary *
//
//  BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8037/25H2/2025Update/HudsonValley2)
//  12th Gen Intel Core i7-12800H 2.40GHz, 1 CPU, 20 logical and 14 physical cores
//
//  .NET SDK 10.0.200
//  [Host]   : .NET 10.0.4 (10.0.4, 10.0.426.12010), X64 RyuJIT x86-64-v3
//  ShortRun : .NET 10.0.4 (10.0.4, 10.0.426.12010), X64 RyuJIT x86-64-v3

//Job=ShortRun  IterationCount=3  LaunchCount=1
//WarmupCount=1

//| Method                                               | Runtime            | Source               | ComparisonType    | Mean       | Error       | StdDev     | Ratio        | RatioSD | Gen0   | Allocated | Alloc Ratio |
//|----------------------------------------------------- |------------------- |--------------------- |------------------ |-----------:|------------:|-----------:|-------------:|--------:|-------:|----------:|------------:|
//| 'ToLower + Contains (with ToLower) - 2x allocations' | .NET 10.0          | ABCDE(...)^&*() [75] | Ordinal           |  28.290 ns |  10.6876 ns |  0.5858 ns |     baseline |         | 0.0140 |     176 B |             |
//| 'string.IndexOf (no alloc)'                          | .NET 10.0          | ABCDE(...)^&*() [75] | Ordinal           |   7.742 ns |   5.4336 ns |  0.2978 ns | 3.66x faster |   0.14x |      - |         - |          NA |
//| 'Span.IndexOf (no alloc, managed path)'              | .NET 10.0          | ABCDE(...)^&*() [75] | Ordinal           |   6.521 ns |   1.4463 ns |  0.0793 ns | 4.34x faster |   0.09x |      - |         - |          NA |
//|                                                      |                    |                      |                   |            |             |            |              |         |        |           |             |
//| 'ToLower + Contains (with ToLower) - 2x allocations' | .NET Framework 4.8 | ABCDE(...)^&*() [75] | Ordinal           | 254.465 ns |  15.4581 ns |  0.8473 ns |     baseline |         | 0.0343 |     217 B |             |
//| 'string.IndexOf (no alloc)'                          | .NET Framework 4.8 | ABCDE(...)^&*() [75] | Ordinal           |  50.547 ns |   6.8980 ns |  0.3781 ns | 5.03x faster |   0.04x |      - |         - |          NA |
//| 'Span.IndexOf (no alloc, managed path)'              | .NET Framework 4.8 | ABCDE(...)^&*() [75] | Ordinal           |  38.318 ns |   7.4586 ns |  0.4088 ns | 6.64x faster |   0.06x |      - |         - |          NA |
//|                                                      |                    |                      |                   |            |             |            |              |         |        |           |             |
//| 'ToLower + Contains (with ToLower) - 2x allocations' | .NET 10.0          | ABCDE(...)^&*() [75] | OrdinalIgnoreCase |  30.575 ns |  13.2449 ns |  0.7260 ns |     baseline |         | 0.0140 |     176 B |             |
//| 'string.IndexOf (no alloc)'                          | .NET 10.0          | ABCDE(...)^&*() [75] | OrdinalIgnoreCase |   8.099 ns |   6.2832 ns |  0.3444 ns | 3.78x faster |   0.16x |      - |         - |          NA |
//| 'Span.IndexOf (no alloc, managed path)'              | .NET 10.0          | ABCDE(...)^&*() [75] | OrdinalIgnoreCase |   6.427 ns |   6.9473 ns |  0.3808 ns | 4.77x faster |   0.26x |      - |         - |          NA |
//|                                                      |                    |                      |                   |            |             |            |              |         |        |           |             |
//| 'ToLower + Contains (with ToLower) - 2x allocations' | .NET Framework 4.8 | ABCDE(...)^&*() [75] | OrdinalIgnoreCase | 269.232 ns | 121.7263 ns |  6.6722 ns |     baseline |         | 0.0343 |     217 B |             |
//| 'string.IndexOf (no alloc)'                          | .NET Framework 4.8 | ABCDE(...)^&*() [75] | OrdinalIgnoreCase | 239.134 ns |  24.5035 ns |  1.3431 ns | 1.13x faster |   0.02x |      - |         - |          NA |
//| 'Span.IndexOf (no alloc, managed path)'              | .NET Framework 4.8 | ABCDE(...)^&*() [75] | OrdinalIgnoreCase | 260.472 ns |  43.7581 ns |  2.3985 ns | 1.03x faster |   0.02x |      - |         - |          NA |
//|                                                      |                    |                      |                   |            |             |            |              |         |        |           |             |
//| 'ToLower + Contains (with ToLower) - 2x allocations' | .NET 10.0          | Lore(...)ris. [191]  | Ordinal           |  44.765 ns |   8.6767 ns |  0.4756 ns |     baseline |         | 0.0325 |     408 B |             |
//| 'string.IndexOf (no alloc)'                          | .NET 10.0          | Lore(...)ris. [191]  | Ordinal           |  13.633 ns |   6.2573 ns |  0.3430 ns | 3.28x faster |   0.08x |      - |         - |          NA |
//| 'Span.IndexOf (no alloc, managed path)'              | .NET 10.0          | Lore(...)ris. [191]  | Ordinal           |  11.595 ns |   2.6312 ns |  0.1442 ns | 3.86x faster |   0.05x |      - |         - |          NA |
//|                                                      |                    |                      |                   |            |             |            |              |         |        |           |             |
//| 'ToLower + Contains (with ToLower) - 2x allocations' | .NET Framework 4.8 | Lore(...)ris. [191]  | Ordinal           | 511.982 ns |  66.4035 ns |  3.6398 ns |     baseline |         | 0.0706 |     449 B |             |
//| 'string.IndexOf (no alloc)'                          | .NET Framework 4.8 | Lore(...)ris. [191]  | Ordinal           | 109.135 ns |  21.9243 ns |  1.2017 ns | 4.69x faster |   0.05x |      - |         - |          NA |
//| 'Span.IndexOf (no alloc, managed path)'              | .NET Framework 4.8 | Lore(...)ris. [191]  | Ordinal           |  94.081 ns |  99.0786 ns |  5.4308 ns | 5.45x faster |   0.28x |      - |         - |          NA |
//|                                                      |                    |                      |                   |            |             |            |              |         |        |           |             |
//| 'ToLower + Contains (with ToLower) - 2x allocations' | .NET 10.0          | Lore(...)ris. [191]  | OrdinalIgnoreCase |  47.911 ns |  31.2295 ns |  1.7118 ns |     baseline |         | 0.0325 |     408 B |             |
//| 'string.IndexOf (no alloc)'                          | .NET 10.0          | Lore(...)ris. [191]  | OrdinalIgnoreCase |  13.196 ns |   1.5312 ns |  0.0839 ns | 3.63x faster |   0.11x |      - |         - |          NA |
//| 'Span.IndexOf (no alloc, managed path)'              | .NET 10.0          | Lore(...)ris. [191]  | OrdinalIgnoreCase |  12.717 ns |   7.0340 ns |  0.3856 ns | 3.77x faster |   0.15x |      - |         - |          NA |
//|                                                      |                    |                      |                   |            |             |            |              |         |        |           |             |
//| 'ToLower + Contains (with ToLower) - 2x allocations' | .NET Framework 4.8 | Lore(...)ris. [191]  | OrdinalIgnoreCase | 506.374 ns | 388.7720 ns | 21.3099 ns |     baseline |         | 0.0706 |     449 B |             |
//| 'string.IndexOf (no alloc)'                          | .NET Framework 4.8 | Lore(...)ris. [191]  | OrdinalIgnoreCase | 513.464 ns |  53.5487 ns |  2.9352 ns | 1.02x slower |   0.04x |      - |         - |          NA |
//| 'Span.IndexOf (no alloc, managed path)'              | .NET Framework 4.8 | Lore(...)ris. [191]  | OrdinalIgnoreCase | 497.864 ns |  36.3594 ns |  1.9930 ns | 1.02x faster |   0.04x |      - |         - |          NA |
//|                                                      |                    |                      |                   |            |             |            |              |         |        |           |             |
//| 'ToLower + Contains (with ToLower) - 2x allocations' | .NET 10.0          | The q(...)y dog [43] | Ordinal           |  24.595 ns |  13.9633 ns |  0.7654 ns |     baseline |         | 0.0089 |     112 B |             |
//| 'string.IndexOf (no alloc)'                          | .NET 10.0          | The q(...)y dog [43] | Ordinal           |   7.513 ns |   0.4483 ns |  0.0246 ns | 3.27x faster |   0.09x |      - |         - |          NA |
//| 'Span.IndexOf (no alloc, managed path)'              | .NET 10.0          | The q(...)y dog [43] | Ordinal           |   5.240 ns |   0.7950 ns |  0.0436 ns | 4.69x faster |   0.13x |      - |         - |          NA |
//|                                                      |                    |                      |                   |            |             |            |              |         |        |           |             |
//| 'ToLower + Contains (with ToLower) - 2x allocations' | .NET Framework 4.8 | The q(...)y dog [43] | Ordinal           | 204.573 ns |  64.9947 ns |  3.5626 ns |     baseline |         | 0.0241 |     152 B |             |
//| 'string.IndexOf (no alloc)'                          | .NET Framework 4.8 | The q(...)y dog [43] | Ordinal           |  43.608 ns |   8.8645 ns |  0.4859 ns | 4.69x faster |   0.08x |      - |         - |          NA |
//| 'Span.IndexOf (no alloc, managed path)'              | .NET Framework 4.8 | The q(...)y dog [43] | Ordinal           |  29.372 ns |   2.4230 ns |  0.1328 ns | 6.97x faster |   0.11x |      - |         - |          NA |
//|                                                      |                    |                      |                   |            |             |            |              |         |        |           |             |
//| 'ToLower + Contains (with ToLower) - 2x allocations' | .NET 10.0          | The q(...)y dog [43] | OrdinalIgnoreCase |  22.419 ns |   5.4077 ns |  0.2964 ns |     baseline |         | 0.0089 |     112 B |             |
//| 'string.IndexOf (no alloc)'                          | .NET 10.0          | The q(...)y dog [43] | OrdinalIgnoreCase |   7.537 ns |   2.8075 ns |  0.1539 ns | 2.98x faster |   0.06x |      - |         - |          NA |
//| 'Span.IndexOf (no alloc, managed path)'              | .NET 10.0          | The q(...)y dog [43] | OrdinalIgnoreCase |   6.158 ns |   1.6943 ns |  0.0929 ns | 3.64x faster |   0.06x |      - |         - |          NA |
//|                                                      |                    |                      |                   |            |             |            |              |         |        |           |             |
//| 'ToLower + Contains (with ToLower) - 2x allocations' | .NET Framework 4.8 | The q(...)y dog [43] | OrdinalIgnoreCase | 206.237 ns |  26.9969 ns |  1.4798 ns |     baseline |         | 0.0241 |     152 B |             |
//| 'string.IndexOf (no alloc)'                          | .NET Framework 4.8 | The q(...)y dog [43] | OrdinalIgnoreCase | 128.457 ns |  12.2357 ns |  0.6707 ns | 1.61x faster |   0.01x |      - |         - |          NA |
//| 'Span.IndexOf (no alloc, managed path)'              | .NET Framework 4.8 | The q(...)y dog [43] | OrdinalIgnoreCase | 145.212 ns |  10.7029 ns |  0.5867 ns | 1.42x faster |   0.01x |      - |         - |          NA |
//


// ---------------------------------------------------------------------------
// LINQPad-compatible configuration
// ---------------------------------------------------------------------------
// BDN's default CsProj toolchain spawns a child process and re-compiles the
// benchmark project from source.  It locates the .csproj by matching the
// output exe name — which breaks under LINQPad because LINQPad compiles
// queries into a temp assembly named "LINQPadQuery" with no .csproj present.
//
// InProcessEmitToolchain avoids this entirely: it runs benchmarks in the
// same process that LINQPad already started, using Reflection.Emit to
// generate the benchmark harness at runtime.  No child process, no .csproj
// lookup, no net48 re-compilation.
//
// Trade-off: because everything runs in one process you cannot benchmark
// startup costs or cross-runtime differences (net48 vs net10) in a single
// run.  Run once per LINQPad target runtime to compare.
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Columns;
using BenchmarkDotNet.Configs;
using BenchmarkDotNet.Engines;
using BenchmarkDotNet.Environments;
using BenchmarkDotNet.Jobs;
using BenchmarkDotNet.Reports;
using BenchmarkDotNet.Running;
using System;


internal sealed class BenchmarkConfig : ManualConfig
{
    public BenchmarkConfig()
    {
        foreach (var logger in DefaultConfig.Instance.GetLoggers()) AddLogger(logger);
        foreach (var exporter in DefaultConfig.Instance.GetExporters()) AddExporter(exporter);
        foreach (var validator in DefaultConfig.Instance.GetValidators()) AddValidator(validator);
        foreach (var analyser in DefaultConfig.Instance.GetAnalysers()) AddAnalyser(analyser);
        foreach (var diagnoser in DefaultConfig.Instance.GetDiagnosers()) AddDiagnoser(diagnoser);
        foreach (var provider in DefaultConfig.Instance.GetColumnProviders()) AddColumnProvider(provider);

        SummaryStyle = SummaryStyle.Default
            .WithRatioStyle(RatioStyle.Trend);

        // Both runtimes defined here with iteration counts pinned explicitly.
        // No [SimpleJob] attributes on the class — this is the single source
        // of truth for job definitions, which prevents duplicate job rows.
        AddJob(Job.ShortRun
            .WithRuntime(ClrRuntime.Net48)
            .WithWarmupCount(1)
            .WithIterationCount(3));

        AddJob(Job.ShortRun
            .WithRuntime(CoreRuntime.Core10_0)
            .WithWarmupCount(1)
            .WithIterationCount(3));
    }
}

// ---------------------------------------------------------------------------
// Benchmark class
// ---------------------------------------------------------------------------

/// <summary>
/// Compares three Contains implementations across runtimes:
///
///   1. StringIndexOf        — string.IndexOf(string, StringComparison)
///                             On net48: may route through Windows NLS / P/Invoke
///                             for OrdinalIgnoreCase and culture-aware comparisons.
///                             On net10.0: reimplemented in managed code; gap narrows.
///
///   2. SpanIndexOf          — source.AsSpan().IndexOf(toCheck.AsSpan(), comparison)
///                             On net48 (System.Memory NuGet): fully managed path,
///                             no P/Invoke, JIT-inlineable, eligible for SIMD
///                             vectorization on supported hardware.
///                             On net10.0: same managed path as string.IndexOf;
///                             numbers should be essentially identical.
///
///   3. ToLowerContains      — the naïve approach included as a worst-case baseline
///                             to anchor the "why we don't do this" discussion.
///                             Allocates two new strings on every call regardless
///                             of runtime.
///
/// The Consumer field is written to after each benchmark body so the JIT
/// cannot dead-code-eliminate the return value (a common source of
/// artificially fast micro-benchmark numbers).
/// </summary>
[Config(typeof(BenchmarkConfig))]
[MemoryDiagnoser]
public class ContainsBenchmarks
{
    // ---------------------------------------------------------------------------
    // Test data — varied lengths exercise both the short-string fast path and
    // the longer SIMD-eligible path in MemoryExtensions.
    // ---------------------------------------------------------------------------

    [Params(
        "The quick brown fox jumps over the lazy dog",
        "ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz 0123456789 !@#$%^&*()",
        "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.")]
    public string Source { get; set; } = string.Empty;

    [Params(StringComparison.OrdinalIgnoreCase, StringComparison.Ordinal)]
    public StringComparison ComparisonType { get; set; }

    // Search term is always present so we measure a successful search,
    // which exercises the full comparison path rather than an early exit.
    private const string ToCheck = "lazy";

    // BenchmarkDotNet's Consumer is a black-hole sink: calling Consume()
    // writes the value into a volatile field, which is enough to prevent
    // the JIT from treating the result as dead code and eliminating the call.
    private readonly Consumer _consumer = new Consumer();

    // ---------------------------------------------------------------------------
    // Benchmarks
    // ---------------------------------------------------------------------------

    /// <summary>
    /// Baseline: the naïve ToLower approach.
    ///
    /// Allocates two strings per call (source.ToLower() + toCheck.ToLower()).
    /// Shown here so the Ratio column in the results makes the cost of
    /// allocations viscerally visible — especially on net48 where GC pressure
    /// from boxed values and string allocations is already a concern.
    /// </summary>
    [Benchmark(Baseline = true, Description = "ToLower + Contains (with ToLower) - 2x allocations")]
    public void ToLowerContains()
    {
        // Allocates: source.ToLower() → new string
        //            toCheck.ToLower() → new string
        // Every. Single. Call.
        bool result = Source.ToLower().Contains(ToCheck.ToLower());
        _consumer.Consume(result);
    }

    /// <summary>
    /// string.IndexOf(string, StringComparison).
    ///
    /// Zero allocation — no new strings created.
    /// On net48, OrdinalIgnoreCase may still route through a Windows NLS
    /// helper (CompareInfo.IndexOf) which involves additional dispatch
    /// overhead compared to the fully-managed Span path.
    /// On net10.0 this was reimplemented to use the same managed searcher
    /// as MemoryExtensions, so the advantage over SpanIndexOf largely
    /// disappears.
    /// </summary>
    [Benchmark(Description = "string.IndexOf (no alloc)")]
    public void StringIndexOf()
    {
        bool result = Source.IndexOf(ToCheck, ComparisonType) != -1;
        _consumer.Consume(result);
    }

    /// <summary>
    /// source.AsSpan().IndexOf(toCheck.AsSpan(), StringComparison).
    ///
    /// Zero allocation — AsSpan() returns a view over the existing string's
    /// memory; no copy, no heap object.
    ///
    /// On net48 (System.Memory NuGet): MemoryExtensions.IndexOf is a
    /// fully-managed implementation that:
    ///   a) avoids the P/Invoke / NLS dispatch that string.IndexOf may use,
    ///   b) is directly inlineable by the JIT because it has no
    ///      MarshalByRefObject or COM interop callsites in the call graph,
    ///   c) on hardware with SSE2/AVX2, the inner loop is SIMD-vectorized,
    ///      processing 16–32 chars per CPU instruction instead of 1.
    ///
    /// On net10.0: both string.IndexOf and Span.IndexOf share the same
    /// underlying managed searcher, so numbers will be essentially identical.
    /// The real story is the net48 column — that's where the gap is visible.
    /// </summary>
    [Benchmark(Description = "Span.IndexOf (no alloc, managed path)")]
    public void SpanIndexOf()
    {
        // AsSpan() — O(1), zero allocation, just a pointer + length struct
        bool result = Source.AsSpan().IndexOf(ToCheck.AsSpan(), ComparisonType) != -1;
        _consumer.Consume(result);
    }

    internal static class Program
    {
        private static void Main(string[] args)
        {
            BenchmarkSwitcher
                .FromAssembly(typeof(Program).Assembly)
                .Run(args, new BenchmarkConfig());
        }
    }
}

## SpanIndexOfBenchmark.csproj
<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <!--
      Multi-target so BenchmarkDotNet can run the same benchmark class
      under both runtimes in a single solution.  The net48 job exercises
      the P/Invoke / NLS code path that string.IndexOf uses on .NET
      Framework; the net10.0 job uses the fully-managed, SIMD-vectorized
      MemoryExtensions path that both string.IndexOf AND Span.IndexOf
      share on modern runtimes — giving us the "before / after" picture
      for the migration conversation.
    -->
    <TargetFrameworks>net48;net10.0</TargetFrameworks>
    <Nullable>enable</Nullable>
    <LangVersion>latest</LangVersion>
    <AllowUnsafeBlocks>false</AllowUnsafeBlocks>
    <Optimize>true</Optimize>
    <OutputType>Exe</OutputType>
    <AssemblyName>SpanIndexOfBenchmark</AssemblyName>
    <RootNamespace>SpanIndexOfBenchmark</RootNamespace>
  </PropertyGroup>

  <ItemGroup>
    <!--
      BenchmarkDotNet — the industry-standard micro-benchmarking library.
      Version 0.14.x supports both net48 and net10.0 out of the box.
    -->
    <PackageReference Include="BenchmarkDotNet" Version="0.15.8" />

    <!--
      System.Memory — required for net48 only.
      This NuGet package back-ports ReadOnlySpan<char>, MemoryExtensions,
      and the managed Span.IndexOf implementation to .NET Framework 4.x.
      On net10.0 the types ship in-box and this reference is ignored.
    -->
    <PackageReference Include="System.Memory" Version="4.6.3" Condition="'$(TargetFramework)' == 'net48'" />
  </ItemGroup>

</Project>

## SpanIndexOfBenchmarks-report-github.md

      
    Raw
  

              SpanIndexOfBenchmarks-report-github.md
            
          
BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8037/25H2/2025Update/HudsonValley2)
12th Gen Intel Core i7-12800H 2.40GHz, 1 CPU, 20 logical and 14 physical cores
.NET SDK 10.0.200
  [Host]   : .NET 10.0.4 (10.0.4, 10.0.426.12010), X64 RyuJIT x86-64-v3
  ShortRun : .NET 10.0.4 (10.0.4, 10.0.426.12010), X64 RyuJIT x86-64-v3

Job=ShortRun  IterationCount=3  LaunchCount=1  
WarmupCount=1  


Method
Runtime
Source
ComparisonType
Mean
Error
StdDev
Ratio
RatioSD
Gen0
Allocated
Alloc Ratio


'ToLower + Contains (with ToLower) - 2x allocations'
.NET 10.0
ABCDE(...)^&*() [75]
Ordinal
25.082 ns
3.9004 ns
0.2138 ns
baseline
****
0.0140
176 B
****


'string.IndexOf (no alloc)'
.NET 10.0
ABCDE(...)^&*() [75]
Ordinal
7.481 ns
6.4782 ns
0.3551 ns
3.36x faster
0.14x
-
-
NA


'Span.IndexOf (no alloc, managed path)'
.NET 10.0
ABCDE(...)^&*() [75]
Ordinal
6.493 ns
1.1292 ns
0.0619 ns
3.86x faster
0.04x
-
-
NA


'ToLower + Contains (with ToLower) - 2x allocations'
.NET Framework 4.8
ABCDE(...)^&*() [75]
Ordinal
254.743 ns
42.4848 ns
2.3287 ns
baseline

0.0343
217 B


'string.IndexOf (no alloc)'
.NET Framework 4.8
ABCDE(...)^&*() [75]
Ordinal
50.518 ns
5.6921 ns
0.3120 ns
5.04x faster
0.05x
-
-
NA


'Span.IndexOf (no alloc, managed path)'
.NET Framework 4.8
ABCDE(...)^&*() [75]
Ordinal
38.280 ns
3.6921 ns
0.2024 ns
6.65x faster
0.06x
-
-
NA


'ToLower + Contains (with ToLower) - 2x allocations'
.NET 10.0
ABCDE(...)^&*() [75]
OrdinalIgnoreCase
25.603 ns
4.5329 ns
0.2485 ns
baseline
****
0.0140
176 B
****


'string.IndexOf (no alloc)'
.NET 10.0
ABCDE(...)^&*() [75]
OrdinalIgnoreCase
8.136 ns
1.4134 ns
0.0775 ns
3.15x faster
0.04x
-
-
NA


'Span.IndexOf (no alloc, managed path)'
.NET 10.0
ABCDE(...)^&*() [75]
OrdinalIgnoreCase
5.576 ns
1.2278 ns
0.0673 ns
4.59x faster
0.06x
-
-
NA


'ToLower + Contains (with ToLower) - 2x allocations'
.NET Framework 4.8
ABCDE(...)^&*() [75]
OrdinalIgnoreCase
250.353 ns
21.6537 ns
1.1869 ns
baseline

0.0343
217 B


'string.IndexOf (no alloc)'
.NET Framework 4.8
ABCDE(...)^&*() [75]
OrdinalIgnoreCase
234.304 ns
19.9322 ns
1.0926 ns
1.07x faster
0.01x
-
-
NA


'Span.IndexOf (no alloc, managed path)'
.NET Framework 4.8
ABCDE(...)^&*() [75]
OrdinalIgnoreCase
248.003 ns
22.2469 ns
1.2194 ns
1.01x faster
0.01x
-
-
NA


'ToLower + Contains (with ToLower) - 2x allocations'
.NET 10.0
Lore(...)ris. [191]
Ordinal
42.247 ns
5.3467 ns
0.2931 ns
baseline
****
0.0325
408 B
****


'string.IndexOf (no alloc)'
.NET 10.0
Lore(...)ris. [191]
Ordinal
12.758 ns
2.1365 ns
0.1171 ns
3.31x faster
0.03x
-
-
NA


'Span.IndexOf (no alloc, managed path)'
.NET 10.0
Lore(...)ris. [191]
Ordinal
11.223 ns
5.4845 ns
0.3006 ns
3.77x faster
0.09x
-
-
NA


'ToLower + Contains (with ToLower) - 2x allocations'
.NET Framework 4.8
Lore(...)ris. [191]
Ordinal
455.926 ns
15.4520 ns
0.8470 ns
baseline

0.0710
449 B


'string.IndexOf (no alloc)'
.NET Framework 4.8
Lore(...)ris. [191]
Ordinal
102.751 ns
13.0885 ns
0.7174 ns
4.44x faster
0.03x
-
-
NA


'Span.IndexOf (no alloc, managed path)'
.NET Framework 4.8
Lore(...)ris. [191]
Ordinal
82.690 ns
14.8784 ns
0.8155 ns
5.51x faster
0.05x
-
-
NA


'ToLower + Contains (with ToLower) - 2x allocations'
.NET 10.0
Lore(...)ris. [191]
OrdinalIgnoreCase
42.508 ns
3.0957 ns
0.1697 ns
baseline
****
0.0325
408 B
****


'string.IndexOf (no alloc)'
.NET 10.0
Lore(...)ris. [191]
OrdinalIgnoreCase
12.107 ns
1.8025 ns
0.0988 ns
3.51x faster
0.03x
-
-
NA


'Span.IndexOf (no alloc, managed path)'
.NET 10.0
Lore(...)ris. [191]
OrdinalIgnoreCase
11.486 ns
3.5957 ns
0.1971 ns
3.70x faster
0.06x
-
-
NA


'ToLower + Contains (with ToLower) - 2x allocations'
.NET Framework 4.8
Lore(...)ris. [191]
OrdinalIgnoreCase
466.615 ns
114.7948 ns
6.2923 ns
baseline

0.0710
449 B


'string.IndexOf (no alloc)'
.NET Framework 4.8
Lore(...)ris. [191]
OrdinalIgnoreCase
467.335 ns
36.2117 ns
1.9849 ns
1.00x slower
0.01x
-
-
NA


'Span.IndexOf (no alloc, managed path)'
.NET Framework 4.8
Lore(...)ris. [191]
OrdinalIgnoreCase
495.846 ns
34.5988 ns
1.8965 ns
1.06x slower
0.01x
-
-
NA


'ToLower + Contains (with ToLower) - 2x allocations'
.NET 10.0
The q(...)y dog [43]
Ordinal
22.623 ns
7.4315 ns
0.4073 ns
baseline
****
0.0089
112 B
****


'string.IndexOf (no alloc)'
.NET 10.0
The q(...)y dog [43]
Ordinal
7.430 ns
11.3120 ns
0.6201 ns
3.06x faster
0.22x
-
-
NA


'Span.IndexOf (no alloc, managed path)'
.NET 10.0
The q(...)y dog [43]
Ordinal
5.144 ns
3.5674 ns
0.1955 ns
4.40x faster
0.16x
-
-
NA


'ToLower + Contains (with ToLower) - 2x allocations'
.NET Framework 4.8
The q(...)y dog [43]
Ordinal
203.347 ns
21.2199 ns
1.1631 ns
baseline

0.0241
152 B


'string.IndexOf (no alloc)'
.NET Framework 4.8
The q(...)y dog [43]
Ordinal
43.209 ns
10.8497 ns
0.5947 ns
4.71x faster
0.06x
-
-
NA


'Span.IndexOf (no alloc, managed path)'
.NET Framework 4.8
The q(...)y dog [43]
Ordinal
29.276 ns
5.5512 ns
0.3043 ns
6.95x faster
0.07x
-
-
NA


'ToLower + Contains (with ToLower) - 2x allocations'
.NET 10.0
The q(...)y dog [43]
OrdinalIgnoreCase
22.914 ns
16.8940 ns
0.9260 ns
baseline
****
0.0089
112 B
****


'string.IndexOf (no alloc)'
.NET 10.0
The q(...)y dog [43]
OrdinalIgnoreCase
7.511 ns
3.3255 ns
0.1823 ns
3.05x faster
0.12x
-
-
NA


'Span.IndexOf (no alloc, managed path)'
.NET 10.0
The q(...)y dog [43]
OrdinalIgnoreCase
6.269 ns
0.4002 ns
0.0219 ns
3.66x faster
0.13x
-
-
NA


'ToLower + Contains (with ToLower) - 2x allocations'
.NET Framework 4.8
The q(...)y dog [43]
OrdinalIgnoreCase
197.499 ns
33.7722 ns
1.8512 ns
baseline

0.0241
152 B


'string.IndexOf (no alloc)'
.NET Framework 4.8
The q(...)y dog [43]
OrdinalIgnoreCase
126.085 ns
28.0671 ns
1.5385 ns
1.57x faster
0.02x
-
-
NA


'Span.IndexOf (no alloc, managed path)'
.NET Framework 4.8
The q(...)y dog [43]
OrdinalIgnoreCase
145.376 ns
19.2963 ns
1.0577 ns
1.36x faster
0.01x
-
-
NA



	// run with:
	// dotnet run -c Release --framework net10.0 -- --filter *




	// * Summary *
	//
	// BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8037/25H2/2025Update/HudsonValley2)
	// 12th Gen Intel Core i7-12800H 2.40GHz, 1 CPU, 20 logical and 14 physical cores
	//
	// .NET SDK 10.0.200
	// [Host] : .NET 10.0.4 (10.0.4, 10.0.426.12010), X64 RyuJIT x86-64-v3
	// ShortRun : .NET 10.0.4 (10.0.4, 10.0.426.12010), X64 RyuJIT x86-64-v3

	//Job=ShortRun IterationCount=3 LaunchCount=1
	//WarmupCount=1

	//\| Method \| Runtime \| Source \| ComparisonType \| Mean \| Error \| StdDev \| Ratio \| RatioSD \| Gen0 \| Allocated \| Alloc Ratio \|
	//\|----------------------------------------------------- \|------------------- \|--------------------- \|------------------ \|-----------:\|------------:\|-----------:\|-------------:\|--------:\|-------:\|----------:\|------------:\|
	//\| 'ToLower + Contains (with ToLower) - 2x allocations' \| .NET 10.0 \| ABCDE(...)^&*() [75] \| Ordinal \| 28.290 ns \| 10.6876 ns \| 0.5858 ns \| baseline \| \| 0.0140 \| 176 B \| \|
	//\| 'string.IndexOf (no alloc)' \| .NET 10.0 \| ABCDE(...)^&*() [75] \| Ordinal \| 7.742 ns \| 5.4336 ns \| 0.2978 ns \| 3.66x faster \| 0.14x \| - \| - \| NA \|
	//\| 'Span.IndexOf (no alloc, managed path)' \| .NET 10.0 \| ABCDE(...)^&*() [75] \| Ordinal \| 6.521 ns \| 1.4463 ns \| 0.0793 ns \| 4.34x faster \| 0.09x \| - \| - \| NA \|
	//\| \| \| \| \| \| \| \| \| \| \| \| \|
	//\| 'ToLower + Contains (with ToLower) - 2x allocations' \| .NET Framework 4.8 \| ABCDE(...)^&*() [75] \| Ordinal \| 254.465 ns \| 15.4581 ns \| 0.8473 ns \| baseline \| \| 0.0343 \| 217 B \| \|
	//\| 'string.IndexOf (no alloc)' \| .NET Framework 4.8 \| ABCDE(...)^&*() [75] \| Ordinal \| 50.547 ns \| 6.8980 ns \| 0.3781 ns \| 5.03x faster \| 0.04x \| - \| - \| NA \|
	//\| 'Span.IndexOf (no alloc, managed path)' \| .NET Framework 4.8 \| ABCDE(...)^&*() [75] \| Ordinal \| 38.318 ns \| 7.4586 ns \| 0.4088 ns \| 6.64x faster \| 0.06x \| - \| - \| NA \|
	//\| \| \| \| \| \| \| \| \| \| \| \| \|
	//\| 'ToLower + Contains (with ToLower) - 2x allocations' \| .NET 10.0 \| ABCDE(...)^&*() [75] \| OrdinalIgnoreCase \| 30.575 ns \| 13.2449 ns \| 0.7260 ns \| baseline \| \| 0.0140 \| 176 B \| \|
	//\| 'string.IndexOf (no alloc)' \| .NET 10.0 \| ABCDE(...)^&*() [75] \| OrdinalIgnoreCase \| 8.099 ns \| 6.2832 ns \| 0.3444 ns \| 3.78x faster \| 0.16x \| - \| - \| NA \|
	//\| 'Span.IndexOf (no alloc, managed path)' \| .NET 10.0 \| ABCDE(...)^&*() [75] \| OrdinalIgnoreCase \| 6.427 ns \| 6.9473 ns \| 0.3808 ns \| 4.77x faster \| 0.26x \| - \| - \| NA \|
	//\| \| \| \| \| \| \| \| \| \| \| \| \|
	//\| 'ToLower + Contains (with ToLower) - 2x allocations' \| .NET Framework 4.8 \| ABCDE(...)^&*() [75] \| OrdinalIgnoreCase \| 269.232 ns \| 121.7263 ns \| 6.6722 ns \| baseline \| \| 0.0343 \| 217 B \| \|
	//\| 'string.IndexOf (no alloc)' \| .NET Framework 4.8 \| ABCDE(...)^&*() [75] \| OrdinalIgnoreCase \| 239.134 ns \| 24.5035 ns \| 1.3431 ns \| 1.13x faster \| 0.02x \| - \| - \| NA \|
	//\| 'Span.IndexOf (no alloc, managed path)' \| .NET Framework 4.8 \| ABCDE(...)^&*() [75] \| OrdinalIgnoreCase \| 260.472 ns \| 43.7581 ns \| 2.3985 ns \| 1.03x faster \| 0.02x \| - \| - \| NA \|
	//\| \| \| \| \| \| \| \| \| \| \| \| \|
	//\| 'ToLower + Contains (with ToLower) - 2x allocations' \| .NET 10.0 \| Lore(...)ris. [191] \| Ordinal \| 44.765 ns \| 8.6767 ns \| 0.4756 ns \| baseline \| \| 0.0325 \| 408 B \| \|
	//\| 'string.IndexOf (no alloc)' \| .NET 10.0 \| Lore(...)ris. [191] \| Ordinal \| 13.633 ns \| 6.2573 ns \| 0.3430 ns \| 3.28x faster \| 0.08x \| - \| - \| NA \|
	//\| 'Span.IndexOf (no alloc, managed path)' \| .NET 10.0 \| Lore(...)ris. [191] \| Ordinal \| 11.595 ns \| 2.6312 ns \| 0.1442 ns \| 3.86x faster \| 0.05x \| - \| - \| NA \|
	//\| \| \| \| \| \| \| \| \| \| \| \| \|
	//\| 'ToLower + Contains (with ToLower) - 2x allocations' \| .NET Framework 4.8 \| Lore(...)ris. [191] \| Ordinal \| 511.982 ns \| 66.4035 ns \| 3.6398 ns \| baseline \| \| 0.0706 \| 449 B \| \|
	//\| 'string.IndexOf (no alloc)' \| .NET Framework 4.8 \| Lore(...)ris. [191] \| Ordinal \| 109.135 ns \| 21.9243 ns \| 1.2017 ns \| 4.69x faster \| 0.05x \| - \| - \| NA \|
	//\| 'Span.IndexOf (no alloc, managed path)' \| .NET Framework 4.8 \| Lore(...)ris. [191] \| Ordinal \| 94.081 ns \| 99.0786 ns \| 5.4308 ns \| 5.45x faster \| 0.28x \| - \| - \| NA \|
	//\| \| \| \| \| \| \| \| \| \| \| \| \|
	//\| 'ToLower + Contains (with ToLower) - 2x allocations' \| .NET 10.0 \| Lore(...)ris. [191] \| OrdinalIgnoreCase \| 47.911 ns \| 31.2295 ns \| 1.7118 ns \| baseline \| \| 0.0325 \| 408 B \| \|
	//\| 'string.IndexOf (no alloc)' \| .NET 10.0 \| Lore(...)ris. [191] \| OrdinalIgnoreCase \| 13.196 ns \| 1.5312 ns \| 0.0839 ns \| 3.63x faster \| 0.11x \| - \| - \| NA \|
	//\| 'Span.IndexOf (no alloc, managed path)' \| .NET 10.0 \| Lore(...)ris. [191] \| OrdinalIgnoreCase \| 12.717 ns \| 7.0340 ns \| 0.3856 ns \| 3.77x faster \| 0.15x \| - \| - \| NA \|
	//\| \| \| \| \| \| \| \| \| \| \| \| \|
	//\| 'ToLower + Contains (with ToLower) - 2x allocations' \| .NET Framework 4.8 \| Lore(...)ris. [191] \| OrdinalIgnoreCase \| 506.374 ns \| 388.7720 ns \| 21.3099 ns \| baseline \| \| 0.0706 \| 449 B \| \|
	//\| 'string.IndexOf (no alloc)' \| .NET Framework 4.8 \| Lore(...)ris. [191] \| OrdinalIgnoreCase \| 513.464 ns \| 53.5487 ns \| 2.9352 ns \| 1.02x slower \| 0.04x \| - \| - \| NA \|
	//\| 'Span.IndexOf (no alloc, managed path)' \| .NET Framework 4.8 \| Lore(...)ris. [191] \| OrdinalIgnoreCase \| 497.864 ns \| 36.3594 ns \| 1.9930 ns \| 1.02x faster \| 0.04x \| - \| - \| NA \|
	//\| \| \| \| \| \| \| \| \| \| \| \| \|
	//\| 'ToLower + Contains (with ToLower) - 2x allocations' \| .NET 10.0 \| The q(...)y dog [43] \| Ordinal \| 24.595 ns \| 13.9633 ns \| 0.7654 ns \| baseline \| \| 0.0089 \| 112 B \| \|
	//\| 'string.IndexOf (no alloc)' \| .NET 10.0 \| The q(...)y dog [43] \| Ordinal \| 7.513 ns \| 0.4483 ns \| 0.0246 ns \| 3.27x faster \| 0.09x \| - \| - \| NA \|
	//\| 'Span.IndexOf (no alloc, managed path)' \| .NET 10.0 \| The q(...)y dog [43] \| Ordinal \| 5.240 ns \| 0.7950 ns \| 0.0436 ns \| 4.69x faster \| 0.13x \| - \| - \| NA \|
	//\| \| \| \| \| \| \| \| \| \| \| \| \|
	//\| 'ToLower + Contains (with ToLower) - 2x allocations' \| .NET Framework 4.8 \| The q(...)y dog [43] \| Ordinal \| 204.573 ns \| 64.9947 ns \| 3.5626 ns \| baseline \| \| 0.0241 \| 152 B \| \|
	//\| 'string.IndexOf (no alloc)' \| .NET Framework 4.8 \| The q(...)y dog [43] \| Ordinal \| 43.608 ns \| 8.8645 ns \| 0.4859 ns \| 4.69x faster \| 0.08x \| - \| - \| NA \|
	//\| 'Span.IndexOf (no alloc, managed path)' \| .NET Framework 4.8 \| The q(...)y dog [43] \| Ordinal \| 29.372 ns \| 2.4230 ns \| 0.1328 ns \| 6.97x faster \| 0.11x \| - \| - \| NA \|
	//\| \| \| \| \| \| \| \| \| \| \| \| \|
	//\| 'ToLower + Contains (with ToLower) - 2x allocations' \| .NET 10.0 \| The q(...)y dog [43] \| OrdinalIgnoreCase \| 22.419 ns \| 5.4077 ns \| 0.2964 ns \| baseline \| \| 0.0089 \| 112 B \| \|
	//\| 'string.IndexOf (no alloc)' \| .NET 10.0 \| The q(...)y dog [43] \| OrdinalIgnoreCase \| 7.537 ns \| 2.8075 ns \| 0.1539 ns \| 2.98x faster \| 0.06x \| - \| - \| NA \|
	//\| 'Span.IndexOf (no alloc, managed path)' \| .NET 10.0 \| The q(...)y dog [43] \| OrdinalIgnoreCase \| 6.158 ns \| 1.6943 ns \| 0.0929 ns \| 3.64x faster \| 0.06x \| - \| - \| NA \|
	//\| \| \| \| \| \| \| \| \| \| \| \| \|
	//\| 'ToLower + Contains (with ToLower) - 2x allocations' \| .NET Framework 4.8 \| The q(...)y dog [43] \| OrdinalIgnoreCase \| 206.237 ns \| 26.9969 ns \| 1.4798 ns \| baseline \| \| 0.0241 \| 152 B \| \|
	//\| 'string.IndexOf (no alloc)' \| .NET Framework 4.8 \| The q(...)y dog [43] \| OrdinalIgnoreCase \| 128.457 ns \| 12.2357 ns \| 0.6707 ns \| 1.61x faster \| 0.01x \| - \| - \| NA \|
	//\| 'Span.IndexOf (no alloc, managed path)' \| .NET Framework 4.8 \| The q(...)y dog [43] \| OrdinalIgnoreCase \| 145.212 ns \| 10.7029 ns \| 0.5867 ns \| 1.42x faster \| 0.01x \| - \| - \| NA \|
	//


	// ---------------------------------------------------------------------------
	// LINQPad-compatible configuration
	// ---------------------------------------------------------------------------
	// BDN's default CsProj toolchain spawns a child process and re-compiles the
	// benchmark project from source. It locates the .csproj by matching the
	// output exe name — which breaks under LINQPad because LINQPad compiles
	// queries into a temp assembly named "LINQPadQuery" with no .csproj present.
	//
	// InProcessEmitToolchain avoids this entirely: it runs benchmarks in the
	// same process that LINQPad already started, using Reflection.Emit to
	// generate the benchmark harness at runtime. No child process, no .csproj
	// lookup, no net48 re-compilation.
	//
	// Trade-off: because everything runs in one process you cannot benchmark
	// startup costs or cross-runtime differences (net48 vs net10) in a single
	// run. Run once per LINQPad target runtime to compare.
	using BenchmarkDotNet.Attributes;
	using BenchmarkDotNet.Columns;
	using BenchmarkDotNet.Configs;
	using BenchmarkDotNet.Engines;
	using BenchmarkDotNet.Environments;
	using BenchmarkDotNet.Jobs;
	using BenchmarkDotNet.Reports;
	using BenchmarkDotNet.Running;
	using System;


	internal sealed class BenchmarkConfig : ManualConfig
	{
	public BenchmarkConfig()
	{
	foreach (var logger in DefaultConfig.Instance.GetLoggers()) AddLogger(logger);
	foreach (var exporter in DefaultConfig.Instance.GetExporters()) AddExporter(exporter);
	foreach (var validator in DefaultConfig.Instance.GetValidators()) AddValidator(validator);
	foreach (var analyser in DefaultConfig.Instance.GetAnalysers()) AddAnalyser(analyser);
	foreach (var diagnoser in DefaultConfig.Instance.GetDiagnosers()) AddDiagnoser(diagnoser);
	foreach (var provider in DefaultConfig.Instance.GetColumnProviders()) AddColumnProvider(provider);

	SummaryStyle = SummaryStyle.Default
	.WithRatioStyle(RatioStyle.Trend);

	// Both runtimes defined here with iteration counts pinned explicitly.
	// No [SimpleJob] attributes on the class — this is the single source
	// of truth for job definitions, which prevents duplicate job rows.
	AddJob(Job.ShortRun
	.WithRuntime(ClrRuntime.Net48)
	.WithWarmupCount(1)
	.WithIterationCount(3));

	AddJob(Job.ShortRun
	.WithRuntime(CoreRuntime.Core10_0)
	.WithWarmupCount(1)
	.WithIterationCount(3));
	}
	}

	// ---------------------------------------------------------------------------
	// Benchmark class
	// ---------------------------------------------------------------------------

	/// <summary>
	/// Compares three Contains implementations across runtimes:
	///
	/// 1. StringIndexOf — string.IndexOf(string, StringComparison)
	/// On net48: may route through Windows NLS / P/Invoke
	/// for OrdinalIgnoreCase and culture-aware comparisons.
	/// On net10.0: reimplemented in managed code; gap narrows.
	///
	/// 2. SpanIndexOf — source.AsSpan().IndexOf(toCheck.AsSpan(), comparison)
	/// On net48 (System.Memory NuGet): fully managed path,
	/// no P/Invoke, JIT-inlineable, eligible for SIMD
	/// vectorization on supported hardware.
	/// On net10.0: same managed path as string.IndexOf;
	/// numbers should be essentially identical.
	///
	/// 3. ToLowerContains — the naïve approach included as a worst-case baseline
	/// to anchor the "why we don't do this" discussion.
	/// Allocates two new strings on every call regardless
	/// of runtime.
	///
	/// The Consumer field is written to after each benchmark body so the JIT
	/// cannot dead-code-eliminate the return value (a common source of
	/// artificially fast micro-benchmark numbers).
	/// </summary>
	[Config(typeof(BenchmarkConfig))]
	[MemoryDiagnoser]
	public class ContainsBenchmarks
	{
	// ---------------------------------------------------------------------------
	// Test data — varied lengths exercise both the short-string fast path and
	// the longer SIMD-eligible path in MemoryExtensions.
	// ---------------------------------------------------------------------------

	[Params(
	"The quick brown fox jumps over the lazy dog",
	"ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz 0123456789 !@#$%^&*()",
	"Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.")]
	public string Source { get; set; } = string.Empty;

	[Params(StringComparison.OrdinalIgnoreCase, StringComparison.Ordinal)]
	public StringComparison ComparisonType { get; set; }

	// Search term is always present so we measure a successful search,
	// which exercises the full comparison path rather than an early exit.
	private const string ToCheck = "lazy";

	// BenchmarkDotNet's Consumer is a black-hole sink: calling Consume()
	// writes the value into a volatile field, which is enough to prevent
	// the JIT from treating the result as dead code and eliminating the call.
	private readonly Consumer _consumer = new Consumer();

	// ---------------------------------------------------------------------------
	// Benchmarks
	// ---------------------------------------------------------------------------

	/// <summary>
	/// Baseline: the naïve ToLower approach.
	///
	/// Allocates two strings per call (source.ToLower() + toCheck.ToLower()).
	/// Shown here so the Ratio column in the results makes the cost of
	/// allocations viscerally visible — especially on net48 where GC pressure
	/// from boxed values and string allocations is already a concern.
	/// </summary>
	[Benchmark(Baseline = true, Description = "ToLower + Contains (with ToLower) - 2x allocations")]
	public void ToLowerContains()
	{
	// Allocates: source.ToLower() → new string
	// toCheck.ToLower() → new string
	// Every. Single. Call.
	bool result = Source.ToLower().Contains(ToCheck.ToLower());
	_consumer.Consume(result);
	}

	/// <summary>
	/// string.IndexOf(string, StringComparison).
	///
	/// Zero allocation — no new strings created.
	/// On net48, OrdinalIgnoreCase may still route through a Windows NLS
	/// helper (CompareInfo.IndexOf) which involves additional dispatch
	/// overhead compared to the fully-managed Span path.
	/// On net10.0 this was reimplemented to use the same managed searcher
	/// as MemoryExtensions, so the advantage over SpanIndexOf largely
	/// disappears.
	/// </summary>
	[Benchmark(Description = "string.IndexOf (no alloc)")]
	public void StringIndexOf()
	{
	bool result = Source.IndexOf(ToCheck, ComparisonType) != -1;
	_consumer.Consume(result);
	}

	/// <summary>
	/// source.AsSpan().IndexOf(toCheck.AsSpan(), StringComparison).
	///
	/// Zero allocation — AsSpan() returns a view over the existing string's
	/// memory; no copy, no heap object.
	///
	/// On net48 (System.Memory NuGet): MemoryExtensions.IndexOf is a
	/// fully-managed implementation that:
	/// a) avoids the P/Invoke / NLS dispatch that string.IndexOf may use,
	/// b) is directly inlineable by the JIT because it has no
	/// MarshalByRefObject or COM interop callsites in the call graph,
	/// c) on hardware with SSE2/AVX2, the inner loop is SIMD-vectorized,
	/// processing 16–32 chars per CPU instruction instead of 1.
	///
	/// On net10.0: both string.IndexOf and Span.IndexOf share the same
	/// underlying managed searcher, so numbers will be essentially identical.
	/// The real story is the net48 column — that's where the gap is visible.
	/// </summary>
	[Benchmark(Description = "Span.IndexOf (no alloc, managed path)")]
	public void SpanIndexOf()
	{
	// AsSpan() — O(1), zero allocation, just a pointer + length struct
	bool result = Source.AsSpan().IndexOf(ToCheck.AsSpan(), ComparisonType) != -1;
	_consumer.Consume(result);
	}

	internal static class Program
	{
	private static void Main(string[] args)
	{
	BenchmarkSwitcher
	.FromAssembly(typeof(Program).Assembly)
	.Run(args, new BenchmarkConfig());
	}
	}
	}
	<Project Sdk="Microsoft.NET.Sdk">

	<PropertyGroup>
	<!--
	Multi-target so BenchmarkDotNet can run the same benchmark class
	under both runtimes in a single solution. The net48 job exercises
	the P/Invoke / NLS code path that string.IndexOf uses on .NET
	Framework; the net10.0 job uses the fully-managed, SIMD-vectorized
	MemoryExtensions path that both string.IndexOf AND Span.IndexOf
	share on modern runtimes — giving us the "before / after" picture
	for the migration conversation.
	-->
	<TargetFrameworks>net48;net10.0</TargetFrameworks>
	<Nullable>enable</Nullable>
	<LangVersion>latest</LangVersion>
	<AllowUnsafeBlocks>false</AllowUnsafeBlocks>
	<Optimize>true</Optimize>
	<OutputType>Exe</OutputType>
	<AssemblyName>SpanIndexOfBenchmark</AssemblyName>
	<RootNamespace>SpanIndexOfBenchmark</RootNamespace>
	</PropertyGroup>

	<ItemGroup>
	<!--
	BenchmarkDotNet — the industry-standard micro-benchmarking library.
	Version 0.14.x supports both net48 and net10.0 out of the box.
	-->
	<PackageReference Include="BenchmarkDotNet" Version="0.15.8" />

	<!--
	System.Memory — required for net48 only.
	This NuGet package back-ports ReadOnlySpan<char>, MemoryExtensions,
	and the managed Span.IndexOf implementation to .NET Framework 4.x.
	On net10.0 the types ship in-box and this reference is ignored.
	-->
	<PackageReference Include="System.Memory" Version="4.6.3" Condition="'$(TargetFramework)' == 'net48'" />
	</ItemGroup>

	</Project>
Method	Runtime	Source	ComparisonType	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Allocated	Alloc Ratio
'ToLower + Contains (with ToLower) - 2x allocations'	.NET 10.0	*ABCDE(...)^&() [75]**	Ordinal	25.082 ns	3.9004 ns	0.2138 ns	baseline	****	0.0140	176 B	****
'string.IndexOf (no alloc)'	.NET 10.0	ABCDE(...)^&*() [75]	Ordinal	7.481 ns	6.4782 ns	0.3551 ns	3.36x faster	0.14x	-	-	NA
'Span.IndexOf (no alloc, managed path)'	.NET 10.0	ABCDE(...)^&*() [75]	Ordinal	6.493 ns	1.1292 ns	0.0619 ns	3.86x faster	0.04x	-	-	NA

'ToLower + Contains (with ToLower) - 2x allocations'	.NET Framework 4.8	ABCDE(...)^&*() [75]	Ordinal	254.743 ns	42.4848 ns	2.3287 ns	baseline		0.0343	217 B
'string.IndexOf (no alloc)'	.NET Framework 4.8	ABCDE(...)^&*() [75]	Ordinal	50.518 ns	5.6921 ns	0.3120 ns	5.04x faster	0.05x	-	-	NA
'Span.IndexOf (no alloc, managed path)'	.NET Framework 4.8	ABCDE(...)^&*() [75]	Ordinal	38.280 ns	3.6921 ns	0.2024 ns	6.65x faster	0.06x	-	-	NA

'ToLower + Contains (with ToLower) - 2x allocations'	.NET 10.0	*ABCDE(...)^&() [75]**	OrdinalIgnoreCase	25.603 ns	4.5329 ns	0.2485 ns	baseline	****	0.0140	176 B	****
'string.IndexOf (no alloc)'	.NET 10.0	ABCDE(...)^&*() [75]	OrdinalIgnoreCase	8.136 ns	1.4134 ns	0.0775 ns	3.15x faster	0.04x	-	-	NA
'Span.IndexOf (no alloc, managed path)'	.NET 10.0	ABCDE(...)^&*() [75]	OrdinalIgnoreCase	5.576 ns	1.2278 ns	0.0673 ns	4.59x faster	0.06x	-	-	NA

'ToLower + Contains (with ToLower) - 2x allocations'	.NET Framework 4.8	ABCDE(...)^&*() [75]	OrdinalIgnoreCase	250.353 ns	21.6537 ns	1.1869 ns	baseline		0.0343	217 B
'string.IndexOf (no alloc)'	.NET Framework 4.8	ABCDE(...)^&*() [75]	OrdinalIgnoreCase	234.304 ns	19.9322 ns	1.0926 ns	1.07x faster	0.01x	-	-	NA
'Span.IndexOf (no alloc, managed path)'	.NET Framework 4.8	ABCDE(...)^&*() [75]	OrdinalIgnoreCase	248.003 ns	22.2469 ns	1.2194 ns	1.01x faster	0.01x	-	-	NA

'ToLower + Contains (with ToLower) - 2x allocations'	.NET 10.0	Lore(...)ris. [191]	Ordinal	42.247 ns	5.3467 ns	0.2931 ns	baseline	****	0.0325	408 B	****
'string.IndexOf (no alloc)'	.NET 10.0	Lore(...)ris. [191]	Ordinal	12.758 ns	2.1365 ns	0.1171 ns	3.31x faster	0.03x	-	-	NA
'Span.IndexOf (no alloc, managed path)'	.NET 10.0	Lore(...)ris. [191]	Ordinal	11.223 ns	5.4845 ns	0.3006 ns	3.77x faster	0.09x	-	-	NA

'ToLower + Contains (with ToLower) - 2x allocations'	.NET Framework 4.8	Lore(...)ris. [191]	Ordinal	455.926 ns	15.4520 ns	0.8470 ns	baseline		0.0710	449 B
'string.IndexOf (no alloc)'	.NET Framework 4.8	Lore(...)ris. [191]	Ordinal	102.751 ns	13.0885 ns	0.7174 ns	4.44x faster	0.03x	-	-	NA
'Span.IndexOf (no alloc, managed path)'	.NET Framework 4.8	Lore(...)ris. [191]	Ordinal	82.690 ns	14.8784 ns	0.8155 ns	5.51x faster	0.05x	-	-	NA

'ToLower + Contains (with ToLower) - 2x allocations'	.NET 10.0	Lore(...)ris. [191]	OrdinalIgnoreCase	42.508 ns	3.0957 ns	0.1697 ns	baseline	****	0.0325	408 B	****
'string.IndexOf (no alloc)'	.NET 10.0	Lore(...)ris. [191]	OrdinalIgnoreCase	12.107 ns	1.8025 ns	0.0988 ns	3.51x faster	0.03x	-	-	NA
'Span.IndexOf (no alloc, managed path)'	.NET 10.0	Lore(...)ris. [191]	OrdinalIgnoreCase	11.486 ns	3.5957 ns	0.1971 ns	3.70x faster	0.06x	-	-	NA

'ToLower + Contains (with ToLower) - 2x allocations'	.NET Framework 4.8	Lore(...)ris. [191]	OrdinalIgnoreCase	466.615 ns	114.7948 ns	6.2923 ns	baseline		0.0710	449 B
'string.IndexOf (no alloc)'	.NET Framework 4.8	Lore(...)ris. [191]	OrdinalIgnoreCase	467.335 ns	36.2117 ns	1.9849 ns	1.00x slower	0.01x	-	-	NA
'Span.IndexOf (no alloc, managed path)'	.NET Framework 4.8	Lore(...)ris. [191]	OrdinalIgnoreCase	495.846 ns	34.5988 ns	1.8965 ns	1.06x slower	0.01x	-	-	NA

'ToLower + Contains (with ToLower) - 2x allocations'	.NET 10.0	The q(...)y dog [43]	Ordinal	22.623 ns	7.4315 ns	0.4073 ns	baseline	****	0.0089	112 B	****
'string.IndexOf (no alloc)'	.NET 10.0	The q(...)y dog [43]	Ordinal	7.430 ns	11.3120 ns	0.6201 ns	3.06x faster	0.22x	-	-	NA
'Span.IndexOf (no alloc, managed path)'	.NET 10.0	The q(...)y dog [43]	Ordinal	5.144 ns	3.5674 ns	0.1955 ns	4.40x faster	0.16x	-	-	NA

'ToLower + Contains (with ToLower) - 2x allocations'	.NET Framework 4.8	The q(...)y dog [43]	Ordinal	203.347 ns	21.2199 ns	1.1631 ns	baseline		0.0241	152 B
'string.IndexOf (no alloc)'	.NET Framework 4.8	The q(...)y dog [43]	Ordinal	43.209 ns	10.8497 ns	0.5947 ns	4.71x faster	0.06x	-	-	NA
'Span.IndexOf (no alloc, managed path)'	.NET Framework 4.8	The q(...)y dog [43]	Ordinal	29.276 ns	5.5512 ns	0.3043 ns	6.95x faster	0.07x	-	-	NA

'ToLower + Contains (with ToLower) - 2x allocations'	.NET 10.0	The q(...)y dog [43]	OrdinalIgnoreCase	22.914 ns	16.8940 ns	0.9260 ns	baseline	****	0.0089	112 B	****
'string.IndexOf (no alloc)'	.NET 10.0	The q(...)y dog [43]	OrdinalIgnoreCase	7.511 ns	3.3255 ns	0.1823 ns	3.05x faster	0.12x	-	-	NA
'Span.IndexOf (no alloc, managed path)'	.NET 10.0	The q(...)y dog [43]	OrdinalIgnoreCase	6.269 ns	0.4002 ns	0.0219 ns	3.66x faster	0.13x	-	-	NA

'ToLower + Contains (with ToLower) - 2x allocations'	.NET Framework 4.8	The q(...)y dog [43]	OrdinalIgnoreCase	197.499 ns	33.7722 ns	1.8512 ns	baseline		0.0241	152 B
'string.IndexOf (no alloc)'	.NET Framework 4.8	The q(...)y dog [43]	OrdinalIgnoreCase	126.085 ns	28.0671 ns	1.5385 ns	1.57x faster	0.02x	-	-	NA
'Span.IndexOf (no alloc, managed path)'	.NET Framework 4.8	The q(...)y dog [43]	OrdinalIgnoreCase	145.376 ns	19.2963 ns	1.0577 ns	1.36x faster	0.01x	-	-	NA