为什么 Regex CompileToAssembly 的性能比已编译的 regex 和 Interpreted Regex 慢？

Question

我正在使用以下代码针对已编译的正则表达式测试 CompileToAssembly 性能，但结果不合适。请让我知道我错过了什么。谢谢！！！

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);
    }

结果如下：

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

Answer 1

您的代码有一个问题：静态字段初始化程序将在运行静态方法之前运行。这意味着在Main() 运行之前已经分配了level4。这意味着level4 引用的对象不是在CompileToAssembly() 中创建的类的实例。

请注意，Regex.CompileToAssembly 的示例代码显示了正则表达式的编译及其在两个不同程序中的使用情况。因此，您作为“CompiledToAssembly”计时的实际正则表达式可能是不同的正则表达式您在之前的测试中编译的。

另一个需要考虑的因素：将程序集加载到内存并将其 jit 到机器代码的开销可能非常大，以至于您需要超过 1,000,000 次迭代才能看到好处。

Answer 2

您正在调试器 (Visual Studio) 下运行。它将防止在加载程序集时发生 JIT 优化。尝试不使用调试器运行 (ctrl-f5)。