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Name		Name	Last commit message	Last commit date
parent directory ..
Benchmarking.csproj		Benchmarking.csproj
HashBenchmark.cs		HashBenchmark.cs
IOOperationsBenchmark.cs		IOOperationsBenchmark.cs
InlineningBenchmarks.cs		InlineningBenchmarks.cs
LinqBenchmark.cs		LinqBenchmark.cs
MatrixBenchmark.cs		MatrixBenchmark.cs
Program.cs		Program.cs
SearchingStringBenchmark.cs		SearchingStringBenchmark.cs
StringBenchmarks.cs		StringBenchmarks.cs
StructVsClass.cs		StructVsClass.cs
SubBufferBenchmarks.cs		SubBufferBenchmarks.cs
ToStringBenchmark.cs		ToStringBenchmark.cs
readme.md		readme.md
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readme.md

Notes for lecture

Sources

• BenchmarkDotNet git repo https://github.com/dotnet/BenchmarkDotNet
• BenchmarkDotNet home https://benchmarkdotnet.org/
• .NET blog performance articles https://devblogs.microsoft.com/dotnet/?s=performance&submit=%EE%9C%A1

Demo

1. Program.cs, benchmark runner, Release, without debug (CTRL+F5), HashBenchmark
2. StringBenchmark What is faster? String concatenation or string builder?
3. SubBufferBenchmarks Keep performace in mind when dealing with large arrays.
   • Performace of some implementations may vary.
   • The fixed statement prevents the garbage collector from relocating a movable variable.
4. SearchingStringBenchmark - Regular expression is generally slower because its overhead (regex engine, expression parsing and compilation if set)
   • However, Regex uses caching so it is faster in this example.
   • We can make it even faster by using RegexOption.Compile
   • More here https://docs.microsoft.com/en-us/dotnet/standard/base-types/details-of-regular-expression-behavior
   • What is complexity of searching? O(m+n) https://en.wikipedia.org/wiki/Knuth%E2%80%93Morris%E2%80%93Pratt_algorithm
5. StructVsClasses - value types are stored on stack, reference types on heap.
   • Reference types bring us fetures like inheritance, polymorphysm, garbage collection,...
   • To do that, they heave special headers on heap (to enable those features).
   • In array, reference types are stored as pointers, value types are directly on that place in memory.
6. ToStringBenchmark - string interpolation is just syntactic sugar for string.Format().
   • If you look at string.Format() it takes string and array of objects https://docs.microsoft.com/en-us/dotnet/api/system.string.format?view=netframework-4.8
   • But a and b are value types on stack, so they need to be boxed (object)a
7. MatrixBenchmark - the trick is in processor cache. In case of j,i it has lot of cache miss making prefetching useless.
   • Small array fit to the L2 cache sot it doesn't have this problem.
8. LinqBenchmark - lambda is in fact delegate and we call this delegate on each item in collection. To make all of this happen, we need lot of allocations.
   • Foreach - Current, MoveNextNext, Dispose.