Looking for a small immutable dictionary with better performance

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Dictionary Is a very common key value pair management data structure . But in the case of demanding performance , Dictionary search speed is not high . therefore , We need a faster solution .

Requirement specification

here , We need a PropertyInfo The mapping relationship corresponding to the delegate , So we can store 《 Looking for better performance dynamics Getter and Setter programme 》 Commission referred to .

therefore , This dictionary has these features ：

1. Once this dictionary is created, it doesn't need to be modified .
2. There are not many dictionary items , Because usually one class There won't be too many attributes .

Solutions that

programme 1,Switch Expression method . Use expressions to generate a containing switch case Statement delegation .

programme 2, Array skip table . We know ,switch case The reason why it is more than continuous if else The reason to be fast is because it generates IL Contains a skip table algorithm . therefore , If we have a way to use consecutive numbers as subscripts , And an array . You can go to C# In the implementation of their own jump table .

Knowledge points

1. Create a delegate using an expression
2. PropertyInfo There is one int MetadataToken attribute , According to current observation , You can know the properties in a type and its MetadataToken It seems to be continuous , Therefore, it can be used as a skip table after taking the module key.
3. The so-called skip watch , It can be simply understood as , Use the subscript of the array to locate a specific element in the array .

Implementation code

here , Let's go straight to the code used in the benchmark .

among ：

• Directly Direct reading , No search
• ArrayIndex Array skip table
• SwitchExp Expression generation Switch programme
• Dic Traditional dictionary scheme

using System; using System.Collections.Generic; using System.Linq; using System.Linq.Expressions; using System.Reflection; using BenchmarkDotNet.Attributes; namespace Newbe.ObjectVisitor.BenchmarkTest { [Config(typeof(Config))] public class FuncSearchTest { private Func<Yueluo, object>[] _target; private readonly Yueluo _yueluo; private readonly Func<Yueluo, string> _func; private readonly PropertyInfo _nameP; private readonly Func<PropertyInfo, Func<Yueluo, object>> _switcher; private readonly Dictionary<PropertyInfo, Func<Yueluo, object>> _dic; public FuncSearchTest() { _yueluo = Yueluo.Create(); var propertyInfos = typeof(Yueluo).GetProperties().ToArray(); CreateCacheArrayD(propertyInfos); _switcher = ValueGetter.CreateGetter<Yueluo, object>(propertyInfos, info => Expression.SwitchCase(Expression.Constant(CreateFunc(info)), Expression.Constant(info))); _dic = propertyInfos.ToDictionary(x => x, CreateFunc); _nameP = typeof(Yueluo).GetProperty(nameof(Yueluo.Name)); _func = x => x.Name; } private void CreateCacheArrayD(IReadOnlyCollection<PropertyInfo> propertyInfos) { _target = new Func<Yueluo, object>[propertyInfos.Count]; foreach (var info in propertyInfos) { var key = GetKey(info); var index = key % propertyInfos.Count; _target[index] = CreateFunc(info); } } private static Func<Yueluo, object> CreateFunc(PropertyInfo info) { var pExp = Expression.Parameter(typeof(Yueluo), "x"); var bodyExp = Expression.Property(pExp, info); var finalExp = Expression.Lambda<Func<Yueluo, object>>(Expression.Convert(bodyExp, typeof(object)), pExp); return finalExp.Compile(); } private static int GetKey(MemberInfo info) { var token = info.MetadataToken; return token; } [Benchmark(Baseline = true)] public string Directly() => _func(_yueluo); [Benchmark] public string ArrayIndex() => (string) _target[_nameP.MetadataToken % _target.Length](_yueluo); [Benchmark] public string SwitchExp() => (string) _switcher(_nameP)(_yueluo); [Benchmark] public string Dic() => (string) _dic[_nameP](_yueluo); } }

The benchmark

BenchmarkDotNet=v0.12.1, OS=Windows 10.0.19041.572 (2004/?/20H1) Intel Xeon CPU E5-2678 v3 2.50GHz, 1 CPU, 24 logical and 12 physical cores .NET Core SDK=5.0.100-rc.2.20479.15 [Host] : .NET Core 2.1.23 (CoreCLR 4.6.29321.03, CoreFX 4.6.29321.01), X64 RyuJIT net461 : .NET Framework 4.8 (4.8.4250.0), X64 RyuJIT net48 : .NET Framework 4.8 (4.8.4250.0), X64 RyuJIT netcoreapp21 : .NET Core 2.1.23 (CoreCLR 4.6.29321.03, CoreFX 4.6.29321.01), X64 RyuJIT netcoreapp31 : .NET Core 3.1.9 (CoreCLR 4.700.20.47201, CoreFX 4.700.20.47203), X64 RyuJIT netcoreapp5 : .NET Core 5.0.0 (CoreCLR 5.0.20.47505, CoreFX 5.0.20.47505), X64 RyuJIT

Conclusion

1. A dictionary is a real drag .
2. Framework Really pulling the hip .
3. Net 5 It's just too strong .
4. Array skipping is the fastest of the indirect schemes .

Chart

data

Method	Job	Runtime	Mean	Error	StdDev	Ratio	RatioSD	Rank
Directly	net461	.NET 4.6.1	0.9347 ns	0.0363 ns	0.0321 ns	1.00	0.00	1
ArrayIndex	net461	.NET 4.6.1	15.0904 ns	0.3820 ns	0.3752 ns	16.13	0.64	2
SwitchExp	net461	.NET 4.6.1	17.1585 ns	0.0624 ns	0.0521 ns	18.30	0.56	3
Dic	net461	.NET 4.6.1	34.3348 ns	0.2447 ns	0.2169 ns	36.77	1.18	4
Directly	net48	.NET 4.8	0.6338 ns	0.0233 ns	0.0218 ns	1.00	0.00	1
ArrayIndex	net48	.NET 4.8	15.3098 ns	0.2794 ns	0.2613 ns	24.17	0.69	2
SwitchExp	net48	.NET 4.8	17.8113 ns	0.0740 ns	0.0656 ns	28.20	0.98	3
Dic	net48	.NET 4.8	33.7930 ns	0.4538 ns	0.4245 ns	53.36	1.64	4
Directly	netcoreapp21	.NET Core 2.1	1.2153 ns	0.1168 ns	0.1434 ns	1.00	0.00	1
ArrayIndex	netcoreapp21	.NET Core 2.1	4.6545 ns	0.1044 ns	0.0871 ns	4.01	0.51	2
SwitchExp	netcoreapp21	.NET Core 2.1	8.1995 ns	0.2567 ns	0.2747 ns	6.81	0.90	3
Dic	netcoreapp21	.NET Core 2.1	24.2669 ns	0.5440 ns	0.5586 ns	20.07	2.51	4
Directly	netcoreapp31	.NET Core 3.1	0.7382 ns	0.1148 ns	0.1074 ns	1.00	0.00	1
ArrayIndex	netcoreapp31	.NET Core 3.1	4.3580 ns	0.1299 ns	0.1085 ns	6.10	0.77	2
SwitchExp	netcoreapp31	.NET Core 3.1	7.5985 ns	0.1310 ns	0.1161 ns	10.45	1.41	3
Dic	netcoreapp31	.NET Core 3.1	22.2433 ns	0.2756 ns	0.2443 ns	30.61	4.20	4
Directly	netcoreapp5	.NET Core 5.0	1.3323 ns	0.0527 ns	0.0493 ns	1.00	0.00	1
ArrayIndex	netcoreapp5	.NET Core 5.0	5.0058 ns	0.1361 ns	0.1206 ns	3.77	0.15	2
SwitchExp	netcoreapp5	.NET Core 5.0	9.0576 ns	0.0985 ns	0.0921 ns	6.81	0.26	3
Dic	netcoreapp5	.NET Core 5.0	20.4052 ns	0.2724 ns	0.2275 ns	15.44	0.59	4

summary

Whether it's array skipping or expression Switch All solutions can solve this problem , And it's faster than using a dictionary .

But there is a problem , At present, the author has not found anything about MetadataToken Whether you really have the same as class The nature of continuity .

Therefore, it is recommended to use Switch Scheme realization .

I'm just a knowledge Porter

• Working with Expression Trees in C#

Release notes

• Newbe.ObjectVisitor 0.2.10 Release , More colorful
• Newbe.ObjectVisitor 0.1.4 Release , The initial release

Use samples

• Newbe.ObjectVisitor Examples 1

Share with others

• Looking for better performance dynamics Getter and Setter programme
• Looking for a smaller immutable dictionary with better performance

GitHub Project address ：https://github.com/newbe36524/Newbe.ObjectVisitor

Gitee Project address ：https://gitee.com/yks/Newbe.ObjectVisitor

 

• The author of this article ： newbe36524
• Link to this article ： https://www.newbe.pro/Newbe.ObjectVisitor/Better-Performance-Small-Map/
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