Project with exercises on code optimization and BenchmarkDotNet.

• 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

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.