我对处理信息解析文本的不同方法了解很多。例如,对于解析整数,可以期待什么样的性能。我想知道是否有人知道这一点。我正在从测试过的人那里寻找一些实数。
在哪种情况下,哪一个提供最佳性能?
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 }
始终使用 T.TryParse(string str,out T value) 。抛出异常的代价很高,如果可以 先验地 处理异常,则应避免抛出异常。使用try- catch块来“节省”性能(因为无效数据速率较低)会滥用异常处理,但会牺牲可维护性和良好的编码习惯。遵循良好的软件工程开发实践,编写测试案例,运行应用程序,然后进行基准测试并进行优化。
“我们应该忘记效率低下的问题,大约有97%的时间是这样: 过早的优化是万恶之源 。但是,我们不应该在那3%的临界水平上放弃自己的机会。” -Donald Knuth
因此,就像在碳信用额度中一样,您任意分配try-catch 的性能 较差 ,而TryParse的性能则 更好 。只有在运行了应用程序并确定我们有某种类型的wrt字符串解析速度减慢之后,我们才考虑使用TryParse以外的任何方法。
(编辑:由于提问者似乎希望定时数据与好的建议一起使用,因此这是请求的定时数据)
用户(对于非信徒)10,000个输入上的各种故障率的时间:
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 /// <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); }