Dictionary Add with key of type Guid vs string

Dictionary_Add_with_key_of_type_Guid_vs_string.linq

[MemoryDiagnoser]
[Config(typeof(DictionaryKeyAddBenchmarks.DictionaryKeyAddBenchmarksConfig))]
public class DictionaryKeyAddBenchmarks
{
	private readonly Consumer _consumer = new Consumer();

	private Guid[] _guidKeys = Array.Empty<Guid>();
	private string[] _string_20_Keys = Array.Empty<string>();
	private string[] _string_50_Keys = Array.Empty<string>();

//	[Params(5_000, 10_000, 50_000)]
	[Params(500, 1_000, 5_000)]
	public int DictionarySize { get; set; }

	[GlobalSetup]
	public void GlobalSetup()
	{
		int count = DictionarySize;
		_guidKeys = new Guid[count];
		for (int i = 0; i < count; i++)
		{
			_guidKeys[i] = Guid.NewGuid();
		}

		_string_20_Keys = CreateUniqueStrings(count, 20, seed: 12345);
		_string_50_Keys = CreateUniqueStrings(count, 50, seed: 54321);
	}

	// baseline enables Ratio (relative factor)
	[Benchmark(Baseline = true)]
	[MethodImpl(MethodImplOptions.NoInlining)]
	public void Add_Guid()
	{
		// use locals to avoid noise from property reads
		int count = DictionarySize;
		
		// create a new dictionary each benchmark run to avoid having to use IterationSetup
		// which should NOT be used for microbenchmarks:
		// https://benchmarkdotnet.org/articles/features/setup-and-cleanup.html#sample-introsetupcleanupiteration
		Dictionary<Guid, int> dictionary = new Dictionary<System.Guid, int>(count);
		Guid[] keys = _guidKeys;
		Consumer consumer = _consumer;

		for (int i = 0; i < count; i++)
		{
			// add throws on duplicate keys
			dictionary.Add(keys[i], i);
			consumer.Consume(i);
		}

		consumer.Consume(dictionary.Count);
	}

	[Benchmark]
	[MethodImpl(MethodImplOptions.NoInlining)]
	public void Add_String_20()
	{
		// use locals to avoid noise from property reads
		int count = DictionarySize;

		// create a new dictionary each benchmark run to avoid having to use IterationSetup
		// which should NOT be used for microbenchmarks:
		// https://benchmarkdotnet.org/articles/features/setup-and-cleanup.html#sample-introsetupcleanupiteration
		Dictionary<string, int> dictionary = new Dictionary<string, int>(count);
		string[] keys = _string_20_Keys;
		Consumer consumer = _consumer;

		for (int i = 0; i < count; i++)
		{
			// add throws on duplicate keys
			dictionary.Add(keys[i], i);
			consumer.Consume(i);
		}

		consumer.Consume(dictionary.Count);
	}

	[Benchmark]
	[MethodImpl(MethodImplOptions.NoInlining)]
	public void Add_String_50()
	{
		// use locals to avoid noise from property reads
		int count = DictionarySize;

		// create a new dictionary each benchmark run to avoid having to use IterationSetup
		// which should NOT be used for microbenchmarks:
		// https://benchmarkdotnet.org/articles/features/setup-and-cleanup.html#sample-introsetupcleanupiteration
		Dictionary<string, int> dictionary = new Dictionary<string, int>(count);
		string[] keys = _string_50_Keys;
		Consumer consumer = _consumer;

		for (int i = 0; i < count; i++)
		{
			// add throws on duplicate keys
			dictionary.Add(keys[i], i);
			consumer.Consume(i);
		}

		consumer.Consume(dictionary.Count);
	}

	private static string[] CreateUniqueStrings(int count, int length, int seed)
	{
		HashSet<string> seen = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
		string[] result = new string[count];

		Random random = new Random(seed);

		//const string alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
		const string alphabet = "abcdefghijklmnopqrstuvwxyz";
		int alphabetLength = alphabet.Length;

		for (int i = 0; i < count; i++)
		{
			while (true)
			{
				char[] chars = new char[length];
				for (int c = 0; c < length; c++)
				{
					chars[c] = alphabet[random.Next(alphabetLength)];
				}

				string candidate = new string(chars);
				if (seen.Add(candidate))
				{
					result[i] = candidate;
					break;
				}
			}
		}

		return result;
	}

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

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

Results_NET_10.0.102.txt

//	Run time: 00:09:49 (589.97 sec), executed benchmarks: 9
//	
// * Summary *
//	BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.7628/25H2/2025Update/HudsonValley2)
//	AMD Ryzen 9 7945HX with Radeon Graphics 2.50GHz, 1 CPU, 32 logical and 16 physical cores
//
//	.NET SDK 10.0.102
//  [Host] : .NET 10.0.2 (10.0.2, 10.0.225.61305), X64 RyuJIT x86-64-v4
//
//| Method        | DictionarySize | Mean       | Error     | StdDev    | Median     | Ratio        | RatioSD |
//|-------------- |--------------- |-----------:|----------:|----------:|-----------:|-------------:|--------:|
//| Add_Guid      | 500            |   2.596 μs | 0.0560 μs | 0.1578 μs |   2.568 μs |     baseline |         |
//| Add_String_20 | 500            |   4.801 μs | 0.0959 μs | 0.1915 μs |   4.798 μs | 1.86x slower |   0.13x |
//| Add_String_50 | 500            |   7.329 μs | 0.1669 μs | 0.4733 μs |   7.179 μs | 2.83x slower |   0.25x |
//|               |                |            |           |           |            |              |         |
//| Add_Guid      | 1000           |   4.961 μs | 0.0989 μs | 0.2518 μs |   4.897 μs |     baseline |         |
//| Add_String_20 | 1000           |   8.864 μs | 0.1769 μs | 0.4307 μs |   8.849 μs | 1.79x slower |   0.12x |
//| Add_String_50 | 1000           |  14.653 μs | 0.6094 μs | 1.7485 μs |  13.979 μs | 2.96x slower |   0.38x |
//|               |                |            |           |           |            |              |         |
//| Add_Guid      | 5000           |  91.310 μs | 1.8140 μs | 3.7462 μs |  91.167 μs |     baseline |         |
//| Add_String_20 | 5000           | 111.300 μs | 2.2225 μs | 6.1215 μs | 111.078 μs | 1.22x slower |   0.08x |
//| Add_String_50 | 5000           | 138.318 μs | 2.7604 μs | 5.7620 μs | 138.342 μs | 1.52x slower |   0.09x |

Results_NETFramework_4.8.1.txt

//	Run time: 00:11:12(672.18 sec), executed benchmarks: 9
//
// * Summary *
//	BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.7628/25H2/2025Update/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        | DictionarySize | Mean       | Error     | StdDev     | Median     | Ratio        | RatioSD |
//|-------------- |--------------- |-----------:|----------:|-----------:|-----------:|-------------:|--------:|
//| Add_Guid      | 500            |   6.566 μs | 0.1643 μs |  0.4660 μs |   6.564 μs |     baseline |         |
//| Add_String_20 | 500            |   7.771 μs | 0.2117 μs |  0.6107 μs |   7.570 μs | 1.19x slower |   0.13x |
//| Add_String_50 | 500            |   9.999 μs | 0.1988 μs |  0.4685 μs |   9.980 μs | 1.53x slower |   0.13x |
//|               |                |            |           |            |            |              |         |
//| Add_Guid      | 1000           |  12.915 μs | 0.2508 μs |  0.2788 μs |  12.908 μs |     baseline |         |
//| Add_String_20 | 1000           |  13.723 μs | 0.2575 μs |  0.3349 μs |  13.753 μs | 1.06x slower |   0.03x |
//| Add_String_50 | 1000           |  20.643 μs | 0.5156 μs |  1.4457 μs |  20.194 μs | 1.60x slower |   0.12x |
//|               |                |            |           |            |            |              |         |
//| Add_Guid      | 5000           | 110.310 μs | 2.2023 μs |  5.8018 μs | 108.866 μs |     baseline |         |
//| Add_String_20 | 5000           | 108.083 μs | 2.6184 μs |  7.5128 μs | 107.593 μs | 1.03x faster |   0.09x |
//| Add_String_50 | 5000           | 157.940 μs | 5.4328 μs | 15.7615 μs | 158.477 μs | 1.44x slower |   0.16x |