iPhone 的高分辨率计时器? [英] High-resolution timer for iPhone?

问题描述

我正在寻找 iPhone 的高分辨率计时代码，以便进行一些性能计时.我想写这样的代码:

I'm looking for high-resolution timing code for iPhone, in order to do some performance timings. I'd like to write code like this:

HighResolutionTimer* myTimer = [[HighResolutionTimer alloc]init];
[myTimer start];
[self doSomeLengthyOperation];
NSLog( @"doSomeLengthyOperation took %f seconds", [myTimer elapsedTime] );

推荐答案

查看 mach/mach_time.h 头文件中的 mach_absolute_time().

Look into mach_absolute_time() in the mach/mach_time.h header.

不要使用 NSDate.当 ntp 做它的事情时，NSDate 甚至不能保证偶尔不会倒退.

Don't use NSDate. NSDate isn't even guaranteed to not go backwards occasionally, when ntp does its thing.

(设备可能有时钟漂移.如果iOS设备快速漂移几秒钟，那么当NTP纠正这个漂移时，你会看到时钟突然倒退几秒钟.非常不利于计时.mach_time使用一个计数器永远不会被 NTP 纠正，因此不能倒退，因此在时间上要好得多.)

(Devices can have clock drift. If the iOS device drifts fast a few seconds, then when NTP corrects this drift, you will see the clock suddenly go backwards a few seconds. Very bad for timing use. mach_time uses a counter that doesn't ever get corrected by NTP, thus can't go backwards, thus is far better for timing.)

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