我对处理解析文本信息的不同方法了解很多.例如,对于解析整数,可以期望什么样的性能.我想知道是否有人知道这方面的任何好的统计数据.我正在寻找一些经过测试的人的真实数字.
在哪些情况下,哪些提供最佳性能？
Parse(...) // Crash if the case is extremely rare .0001%
If (SomethingIsValid) // Check the value before parsing
Parse(...)
TryParse(...) // Using TryParse
try
{
Parse(...)
}
catch
{
// Catch any thrown exceptions
}
user7116.. 62
始终使用T.TryParse(string str,out T value).抛出异常是昂贵的,如果你能够先验地处理这种情况,应该避免.使用try-catch块来"保存"性能(因为您的无效数据速率很低)是滥用异常处理,但代价是可维护性和良好的编码实践.遵循合理的软件工程开发实践,编写测试用例,运行应用程序,然后进行基准测试和优化.
"我们应该忘记小的效率,大约97%的时间说:过早的优化是所有邪恶的根源.但我们不应该放弃我们在那个关键的3%的机会"-Donald Knuth
因此,您可以在碳信用额中任意分配try-catch 的性能更差,并且TryParse的性能更好.只有在我们运行我们的应用程序并确定我们有某种减速wrt字符串解析之后,我们才会考虑使用除TryParse之外的任何东西.
(编辑:因为看起来提问者希望时间数据有良好的建议,这里是要求的时间数据)
来自用户的10,000个输入(针对非信徒)的各种失败率的时间:
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 /// Rate of errors in user input ///Total time taken 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; } /// Rate of errors in user input ///Total time taken 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); }
亚里士多德从来没有通过实验来弄脏手.惭愧,羞耻.你需要断言一些事情显然是真的.这是互联网的方式! (2认同)
Kev.. 8
虽然我没有亲自描述不同的方式,但这个章节有:
http://blogs.msdn.com/ianhu/archive/2005/12/19/505702.aspx
始终使用T.TryParse(string str,out T value).抛出异常是昂贵的,如果你能够先验地处理这种情况,应该避免.使用try-catch块来"保存"性能(因为您的无效数据速率很低)是滥用异常处理,但代价是可维护性和良好的编码实践.遵循合理的软件工程开发实践,编写测试用例,运行应用程序,然后进行基准测试和优化.
"我们应该忘记小的效率,大约97%的时间说:过早的优化是所有邪恶的根源.但我们不应该放弃我们在那个关键的3%的机会"-Donald Knuth
因此,您可以在碳信用额中任意分配try-catch 的性能更差,并且TryParse的性能更好.只有在我们运行我们的应用程序并确定我们有某种减速wrt字符串解析之后,我们才会考虑使用除TryParse之外的任何东西.
(编辑:因为看起来提问者希望时间数据有良好的建议,这里是要求的时间数据)
来自用户的10,000个输入(针对非信徒)的各种失败率的时间:
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 /// Rate of errors in user input ///Total time taken 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; } /// Rate of errors in user input ///Total time taken 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); }
虽然我没有亲自描述不同的方式,但这个章节有:
http://blogs.msdn.com/ianhu/archive/2005/12/19/505702.aspx
Try-Catch总是会慢一些.TryParse会更快.
IF和TryParse是相同的.
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