Why Regex CompileToAssembly giving slower performance than compiled regex and Interpreted Regex?
.net, c#, regex
Solution
Your code has a problem: static field initializers will run before static methods run. That means that `level4` has already been assigned before `Main()` runs. This means that the object referred to by `level4` is not an instance of the class created in `CompileToAssembly()`.
Note that the example code for `Regex.CompileToAssembly` shows the compilation of the regex and its consumption in two different programs. The actual regex you're timing as "CompiledToAssembly" could therefore be a different regex that you compiled in an earlier test.
Another factor to consider: the overhead of loading an assembly into memory and jitting it to machine code might be significant enough that you need more than 1,000,000 iterations to see a benefit.
Problem
I am using the following code to test CompileToAssembly performance against compiled regex but the results are not appropriate. Please let me know what am I missing. Thanks!!! ``` static readonly Regex regex = new Regex(@"(stats|pause\s?(all|\d+(\,\d+)*)|start\s?(all|\d+(\,\d+)*)|add\s?time\s?(all|\d+(\,\d+)*)(\s\d+)|c(?:hange)?\s?p(?:asskey)?|close)(.*)", RegexOptions.Compiled); static readonly Regex reg = new Regex(@"(stats|pause\s?(all|\d+(\,\d+)*)|start\s?(all|\d+(\,\d+)*)|add\s?time\s?(all|\d+(\,\d+)*)(\s\d+)|c(?:hange)?\s?p(?:asskey)?|close)(.*)"); static readonly Regex level4 = new DuplicatedString(); static void Main() { const string str = "add time 243,3453,43543,543,534534,54534543,345345,4354354235,345435,34543534 6873brekgnfkjerkgiengklewrij"; const int itr = 1000000; CompileToAssembly(); Match match; Stopwatch sw = new Stopwatch(); sw.Start(); for (int i = 0; i < itr; i++) { match = regex.Match(str); } sw.Stop(); Console.WriteLine("RegexOptions.Compiled: {0}ms", sw.ElapsedMilliseconds); sw.Reset(); sw.Start(); for (int i = 0; i < itr; i++) { match = level4.Match(str); } sw.Stop(); Console.WriteLine("CompiledToAssembly: {0}ms", sw.ElapsedMilliseconds); sw.Reset(); sw.Start(); for (int i = 0; i < itr; i++) { match = reg.Match(str); } sw.Stop(); Console.WriteLine("Interpreted: {0}ms", sw.ElapsedMilliseconds); Console.ReadLine(); } public static void CompileToAssembly() { RegexCompilationInfo expr; List<RegexCompilationInfo> compilationList = new List<RegexCompilationInfo>(); // Define regular expression to detect duplicate words expr = new RegexCompilationInfo(@"(stats|pause\s?(all|\d+(\,\d+)*)|start\s?(all|\d+(\,\d+)*)|add\s?time\s?(all|\d+(\,\d+)*)(\s\d+)|c(?:hange)?\s?p(?:asskey)?|close)(.*)", RegexOptions.Compiled, "DuplicatedString", "Utilities.RegularExpressions", true); // Add info object to list of objects compilationList.Add(expr); // Apply AssemblyTitle attribute to the new assembly // // Define the parameter(s) of the AssemblyTitle attribute's constructor Type[] parameters = { typeof(string) }; // Define the assembly's title object[] paramValues = { "General-purpose library of compiled regular expressions" }; // Get the ConstructorInfo object representing the attribute's constructor ConstructorInfo ctor = typeof(System.Reflection.AssemblyTitleAttribute).GetConstructor(parameters); // Create the CustomAttributeBuilder object array CustomAttributeBuilder[] attBuilder = { new CustomAttributeBuilder(ctor, paramValues) }; // Generate assembly with compiled regular expressions RegexCompilationInfo[] compilationArray = new RegexCompilationInfo[compilationList.Count]; AssemblyName assemName = new AssemblyName("RegexLib, Version=1.0.0.1001, Culture=neutral, PublicKeyToken=null"); compilationList.CopyTo(compilationArray); Regex.CompileToAssembly(compilationArray, assemName, attBuilder); } ``` following are the results: ``` RegexOptions.Compiled: 3908ms CompiledToAssembly: 59349ms Interpreted: 5653ms ```