爲什麼Regex CompileToAssembly的性能比編譯正則表達式和解釋正則表達式慢？

Question

我正在使用以下代碼來測試編譯正則表達式的CompileToAssembly性能，但結果不合適。請讓我知道我錯過了什麼。謝謝！！！

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); 
    } 

以下是結果：

RegexOptions.Compiled: 3908ms 
CompiledToAssembly: 59349ms 
Interpreted: 5653ms 

Answer 1

你的代碼中有一個問題：靜態字段初始運行前靜態方法運行。這意味着level4已在Main()運行之前分配。這意味着level4引用的對象是而不是在CompileToAssembly()中創建的類的實例。

請注意，Regex.CompileToAssembly的示例代碼顯示了編譯正則表達式及其在兩種不同程序中的消耗。因此，您計時爲「CompiledToAssembly」的實際正則表達式可能是您在早期測試中編譯的不同正則表達式。

另一個需要考慮的因素是：將程序集加載到內存中並將其加載到機器代碼的開銷可能足夠大，以至於需要超過1,000,000次迭代才能看到好處。

Answer 2

您正在調試器（Visual Studio）下運行。它會阻止裝載程序集時發生JIT優化。嘗試在沒有調試器的情況下運行（ctrl-f5）。