解析性能（如，的TryParse，尝试捕获）

问题描述

我知道很多关于处理信息解析文本的不同方式。解析例如整数，可以预期什么样的表现。我想知道，如果有人对此有任何好的统计都知道。我要寻找从别人一些真正的数字谁也测试了这一点。

哪个这些优惠的最佳性能在哪些情况？

 解析（...）//如果崩溃的情况是极为罕见的0.0001％如果（SomethingIsValid）//解析之前检查值
    解析（...）的TryParse（...）//使用的TryParse尝试
{
    解析（...）
}
抓住
{
    //捕获任何抛出的异常
}
 

解决方案

总是使用 T.TryParse（字符串str出的T值）。抛出异常是昂贵的，应该尽量避免，如果你能处理这种情况的先验的。使用try-catch块性能拯救（因为你的无效数据率低）是例外的可维护性为代价处理和良好的编码实践的滥用。按照完善的软件工程开发实践，编写测试用例，运行你的应用程序，然后基准和优化。

Therefore you assign, arbitrarily like in carbon credits, that the performance of try-catch is worse and that the performance of TryParse is better. Only after we've run our application and determined that we have some sort of slowdown w.r.t. string parsing would we even consider using anything other than TryParse.

(edit: since it appears the questioner wanted timing data to go with good advice, here is the timing data requested)

Times for various failure rates on 10,000 inputs from the user (for the unbelievers):

Failure Rate      Try-Catch          TryParse        Slowdown
  0%           00:00:00.0131758   00:00:00.0120421      0.1
 10%           00:00:00.1540251   00:00:00.0087699     16.6
 20%           00:00:00.2833266   00:00:00.0105229     25.9
 30%           00:00:00.4462866   00:00:00.0091487     47.8
 40%           00:00:00.6951060   00:00:00.0108980     62.8
 50%           00:00:00.7567745   00:00:00.0087065     85.9
 60%           00:00:00.7090449   00:00:00.0083365     84.1
 70%           00:00:00.8179365   00:00:00.0088809     91.1
 80%           00:00:00.9468898   00:00:00.0088562    105.9
 90%           00:00:01.0411393   00:00:00.0081040    127.5
100%           00:00:01.1488157   00:00:00.0078877    144.6


/// <param name="errorRate">Rate of errors in user input</param>
/// <returns>Total time taken</returns>
public static TimeSpan TimeTryCatch(double errorRate, int seed, int count)
{
    Stopwatch stopwatch = new Stopwatch();
    Random random = new Random(seed);
    string bad_prefix = @"X";

    stopwatch.Start();
    for(int ii = 0; ii < count; ++ii)
    {
        string input = random.Next().ToString();
        if (random.NextDouble() < errorRate)
        {
           input = bad_prefix + input;
        }

        int value = 0;
        try
        {
            value = Int32.Parse(input);
        }
        catch(FormatException)
        {
            value = -1; // we would do something here with a logger perhaps
        }
    }
    stopwatch.Stop();

    return stopwatch.Elapsed;
}

/// <param name="errorRate">Rate of errors in user input</param>
/// <returns>Total time taken</returns>
public static TimeSpan TimeTryParse(double errorRate, int seed, int count)
{
    Stopwatch stopwatch = new Stopwatch();
    Random random = new Random(seed);
    string bad_prefix = @"X";

    stopwatch.Start();
    for(int ii = 0; ii < count; ++ii)
    {
        string input = random.Next().ToString();
        if (random.NextDouble() < errorRate)
        {
           input = bad_prefix + input;
        }

        int value = 0;
        if (!Int32.TryParse(input, out value))
        {
            value = -1; // we would do something here with a logger perhaps
        }
    }
    stopwatch.Stop();

    return stopwatch.Elapsed;
}

public static void TimeStringParse()
{
    double errorRate = 0.1; // 10% of the time our users mess up
    int count = 10000; // 10000 entries by a user

    TimeSpan trycatch = TimeTryCatch(errorRate, 1, count);
    TimeSpan tryparse = TimeTryParse(errorRate, 1, count);

    Console.WriteLine("trycatch: {0}", trycatch);
    Console.WriteLine("tryparse: {0}", tryparse);
}

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