适用于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，以便做一些性能计时。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中的mach_absolute_time（）。 h header。

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

不要使用NSDate。当ntp完成它时，NSDate甚至不会保证不会倒退。

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，然后当NTP纠正这种漂移时，你会看到时钟突然向后退了几秒钟。时间使用非常糟糕.mach_time使用的计数器不会被NTP纠正，因此不能倒退，因此要好得多时间安排。）

(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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