不要试图损害性能/ catch块时异常不抛出？ [英] Do try/catch blocks hurt performance when exceptions are not thrown?

问题描述

在与我们遇到了一大段code的来了一个尝试{} 块内的微软员工一个code审查。她和一个IT重新presentative建议这会对code性能的影响。事实上，他们建议大部分code应该是try / catch块之外，那只有重要路段应进行检查。微软员工加入并表示即将到来的白皮书警告不要不正确try / catch块。

During a code review with a Microsoft employee we came across a large section of code inside a try{} block. She and an IT representative suggested this can have effects on performance of the code. In fact, they suggested most of the code should be outside of try/catch blocks, and that only important sections should be checked. The Microsoft employee added and said an upcoming white paper warns against incorrect try/catch blocks.

我环顾四周，发现它<一个href=\"http://msmvps.com/blogs/peterritchie/archive/2007/06/22/performance-implications-of-try-catch-finally.aspx\">can影响优化，但它似乎当一个变量的作用域之间共享才适用。

I've looked around and found it can affect optimizations, but it seems to only apply when a variable is shared between scopes.

我不要求有关code的维护，甚至处理正确的异常（有问题的code需要重新分解，毫无疑问）。我还没有提到使用异常流量控制，这是在大多数情况下，显然是错误的。这些都是重要的问题（有些是更重要的），而不是这里的重点。

I'm not asking about maintainability of the code, or even handling the right exceptions (the code in question needs re-factoring, no doubt). I'm also not referring to using exceptions for flow control, this is clearly wrong in most cases. Those are important issues (some are more important), but not the focus here.

如何try / catch块影响性能的时候例外的不的抛出？

How do try/catch blocks affect performance when exceptions are not thrown?

编辑：我加入悬赏。还有有趣的反应，但我想获得一些更多的投入。

I'm adding a bounty. There are interesting responses, but I would like to get some more input.

推荐答案

检查一下。

static public void Main(string[] args)
{
    Stopwatch w = new Stopwatch();
    double d = 0;

    w.Start();

    for (int i = 0; i < 10000000; i++)
    {
        try
        {
            d = Math.Sin(1);
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.ToString());
        }
    }

    w.Stop();
    Console.WriteLine(w.Elapsed);
    w.Reset();
    w.Start();

    for (int i = 0; i < 10000000; i++)
    {
        d = Math.Sin(1);
    }

    w.Stop();
    Console.WriteLine(w.Elapsed);
}

输出：

00:00:00.4269033  // with try/catch
00:00:00.4260383  // without.

在毫秒：

449
416

新的code：

for (int j = 0; j < 10; j++)
{
    Stopwatch w = new Stopwatch();
    double d = 0;
    w.Start();

    for (int i = 0; i < 10000000; i++)
    {
        try
        {
            d = Math.Sin(d);
        }

        catch (Exception ex)
        {
            Console.WriteLine(ex.ToString());
        }

        finally
        {
            d = Math.Sin(d);
        }
    }

    w.Stop();
    Console.Write("   try/catch/finally: ");
    Console.WriteLine(w.ElapsedMilliseconds);
    w.Reset();
    d = 0;
    w.Start();

    for (int i = 0; i < 10000000; i++)
    {
        d = Math.Sin(d);
        d = Math.Sin(d);
    }

    w.Stop();
    Console.Write("No try/catch/finally: ");
    Console.WriteLine(w.ElapsedMilliseconds);
    Console.WriteLine();
}

新的结果：

   try/catch/finally: 382
No try/catch/finally: 332

   try/catch/finally: 375
No try/catch/finally: 332

   try/catch/finally: 376
No try/catch/finally: 333

   try/catch/finally: 375
No try/catch/finally: 330

   try/catch/finally: 373
No try/catch/finally: 329

   try/catch/finally: 373
No try/catch/finally: 330

   try/catch/finally: 373
No try/catch/finally: 352

   try/catch/finally: 374
No try/catch/finally: 331

   try/catch/finally: 380
No try/catch/finally: 329

   try/catch/finally: 374
No try/catch/finally: 334

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