Benchmark comparing for vs foreach on List<int> using .NET 10 x64 vs .NET Framework 4.8.1 x64 RyuJIT vs .NET Framework 4.8.1 x86 LegacyJIT

IterationBenchmarks_for_vs_foreach_ValueType.linq

[MemoryDiagnoser]
[GroupBenchmarksBy(BenchmarkLogicalGroupRule.ByCategory)]
[Config(typeof(IterationBenchmarks_for_vs_foreach_ValueType.IterationBenchmarksConfig))]
public class IterationBenchmarks_for_vs_foreach_ValueType
{
	[Params(1_000, 10_000, 50_000)]
	public int Count;

	private List<int> _listOfInt = null;
	private Consumer _consumer = null;

	[GlobalSetup]
	public void GlobalSetup()
	{
		_listOfInt = new List<int>(Count);
		Random random = new Random(42);
		for (int i = 0; i < Count; i++)
		{
			_listOfInt.Add(random.Next());
		}

		_consumer = new Consumer();
	}

	[Benchmark(Description = "List<int> for with hoisted Count")]
//	[MethodImpl(MethodImplOptions.NoInlining)]
	public void List_For_With_Hoisted_Count()
	{
		int hoistedCount = _listOfInt.Count;
		for (int i = 0; i < hoistedCount; i++)
		{
			int value = _listOfInt[i];
			_consumer.Consume(value);
		}
	}

	[Benchmark(Description = "List<int> for")]
//	[MethodImpl(MethodImplOptions.NoInlining)]
	public void List_For()
	{
		for (int i = 0; i < _listOfInt.Count; i++)
		{
			int value = _listOfInt[i];
			_consumer.Consume(value);
		}
	}

	[Benchmark(Baseline = true, Description = "List<int> foreach")]
//	[MethodImpl(MethodImplOptions.NoInlining)]
	public void List_Foreach()
	{
		foreach (int item in _listOfInt)
		{
			_consumer.Consume(item);
		}
	}

	private class IterationBenchmarksConfig : ManualConfig
	{
		public IterationBenchmarksConfig()
		{
			SummaryStyle = BenchmarkDotNet.Reports.SummaryStyle.Default.WithRatioStyle(RatioStyle.Trend);
		}
	}
}

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

Results_x64_RyuJIT_NETFramework_4.8.1.txt

//	Global total time: 00:08:13 (493.27 sec), executed benchmarks: 9
//
// * Summary *
//
//	BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.7840/25H2/2025Update/HudsonValley2)
//	AMD Ryzen 9 7945HX with Radeon Graphics 2.50GHz, 1 CPU, 32 logical and 16 physical cores
//
//  [Host]     : .NET Framework 4.8.1 (4.8.9221.0), X64 RyuJIT VectorSize=256
//  DefaultJob : .NET Framework 4.8.1 (4.8.9221.0), X64 RyuJIT VectorSize=256
//
//| Method                             | Count | Mean        | Error       | StdDev      | Ratio        | RatioSD |
//|----------------------------------- |------ |------------:|------------:|------------:|-------------:|--------:|
//| 'List<int> for with hoisted Count' | 1000  |    648.8 ns |     7.56 ns |     6.71 ns | 2.42x faster |   0.14x |
//| 'List<int> for'                    | 1000  |    811.2 ns |    15.92 ns |    18.33 ns | 1.94x faster |   0.12x |
//| 'List<int> foreach'                | 1000  |  1,570.0 ns |    31.19 ns |    87.47 ns |     baseline |         |
//|                                    |       |             |             |             |              |         |
//| 'List<int> for with hoisted Count' | 10000 |  7,237.9 ns |   143.83 ns |   280.52 ns | 1.98x faster |   0.10x |
//| 'List<int> for'                    | 10000 |  8,271.9 ns |   164.82 ns |   437.08 ns | 1.73x faster |   0.11x |
//| 'List<int> foreach'                | 10000 | 14,292.0 ns |   285.05 ns |   528.36 ns |     baseline |         |
//|                                    |       |             |             |             |              |         |
//| 'List<int> for with hoisted Count' | 50000 | 35,703.6 ns |   712.24 ns |   926.12 ns | 1.95x faster |   0.08x |
//| 'List<int> for'                    | 50000 | 39,753.5 ns |   790.27 ns | 2,216.00 ns | 1.76x faster |   0.11x |
//| 'List<int> foreach'                | 50000 | 69,590.0 ns | 1,388.87 ns | 2,320.49 ns |     baseline |         |

Results_x86_LegacyJIT_NETFramework_4.8.1.txt

//	Global total time: 00:08:50 (530.02 sec), executed benchmarks: 9
//
// * Summary *
//
//	BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.7840/25H2/2025Update/HudsonValley2)
//	AMD Ryzen 9 7945HX with Radeon Graphics 2.50GHz, 1 CPU, 32 logical and 16 physical cores
//
//  [Host]     : .NET Framework 4.8.1 (4.8.9221.0), X86 LegacyJIT
//  DefaultJob : .NET Framework 4.8.1 (4.8.9221.0), X86 LegacyJIT
//
//| Method                             | Count | Mean        | Error       | StdDev      | Ratio        | RatioSD |
//|----------------------------------- |------ |------------:|------------:|------------:|-------------:|--------:|
//| 'List<int> for with hoisted Count' | 1000  |    617.7 ns |    12.00 ns |    17.59 ns | 2.52x faster |   0.10x |
//| 'List<int> for'                    | 1000  |    714.8 ns |    13.89 ns |    18.54 ns | 2.18x faster |   0.08x |
//| 'List<int> foreach'                | 1000  |  1,555.4 ns |    29.82 ns |    39.81 ns |     baseline |         |
//|                                    |       |             |             |             |              |         |
//| 'List<int> for with hoisted Count' | 10000 |  7,189.5 ns |   143.07 ns |   384.36 ns | 2.37x faster |   0.18x |
//| 'List<int> for'                    | 10000 |  8,192.6 ns |   162.94 ns |   367.79 ns | 2.07x faster |   0.15x |
//| 'List<int> foreach'                | 10000 | 16,965.2 ns |   338.25 ns |   948.50 ns |     baseline |         |
//|                                    |       |             |             |             |              |         |
//| 'List<int> for with hoisted Count' | 50000 | 36,505.7 ns |   889.86 ns | 2,581.66 ns | 2.30x faster |   0.20x |
//| 'List<int> for'                    | 50000 | 39,884.4 ns |   855.76 ns | 2,509.80 ns | 2.10x faster |   0.17x |
//| 'List<int> foreach'                | 50000 | 83,468.6 ns | 1,664.93 ns | 4,176.99 ns |     baseline |         |

x64_Results_NET_10.0.103.txt

NOTE that multiple runs sometimes produced results where foreach was slightly faster.
I attribute this to the measurement noise of StdDev.
This flip-flop did NOT happen in the .NET Framework 4.8.1 benchmark results

//	Global total time: 00:07:23 (443.34 sec), executed benchmarks: 9
//
// * Summary *
//
//	BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.7840/25H2/2025Update/HudsonValley2)
//	AMD Ryzen 9 7945HX with Radeon Graphics 2.50GHz, 1 CPU, 32 logical and 16 physical cores
//
//	.NET SDK 10.0.103
//  [Host] : .NET 10.0.3 (10.0.3, 10.0.326.7603), X64 RyuJIT x86-64-v4
//
//| Method                             | Count | Mean        | Error     | StdDev      | Ratio        | RatioSD |
//|----------------------------------- |------ |------------:|----------:|------------:|-------------:|--------:|
//| 'List<int> for with hoisted Count' | 1000  |    647.9 ns |  12.86 ns |    27.96 ns | 1.01x slower |   0.08x |
//| 'List<int> for'                    | 1000  |    865.4 ns |  17.15 ns |    47.23 ns | 1.34x slower |   0.12x |
//| 'List<int> foreach'                | 1000  |    647.3 ns |  14.97 ns |    43.90 ns |     baseline |         |
//|                                    |       |             |           |             |              |         |
//| 'List<int> for with hoisted Count' | 10000 |  6,530.4 ns | 128.99 ns |   242.27 ns | 1.06x slower |   0.06x |
//| 'List<int> for'                    | 10000 |  7,874.7 ns | 156.28 ns |   440.78 ns | 1.28x slower |   0.09x |
//| 'List<int> foreach'                | 10000 |  6,180.4 ns | 119.06 ns |   287.55 ns |     baseline |         |
//|                                    |       |             |           |             |              |         |
//| 'List<int> for with hoisted Count' | 50000 | 32,936.5 ns | 950.65 ns | 2,803.02 ns | 1.04x faster |   0.12x |
//| 'List<int> for'                    | 50000 | 41,521.8 ns | 826.11 ns | 2,041.95 ns | 1.23x slower |   0.11x |
//| 'List<int> foreach'                | 50000 | 34,022.1 ns | 857.86 ns | 2,529.41 ns |     baseline |         |