iOS 计算代码块执行时间

#import <mach/mach_time.h> // for mach_absolute_timedouble MachTimeToSecs(uint64_t time){    mach_timebase_info_data_t timebase;    mach_timebase_info(&timebase);    return (double)time * (double)timebase.numer /  (double)timebase.denom / 1e9;}- (void)profileDoSomething{      uint64_t begin = mach_absolute_time();    [self doSomething];    uint64_t end = mach_absolute_time();    NSLog(@"Time taken to doSomething %g s", MachTimeToSecs(end - begin));}

方法二：

方法一：使用系统时间NSDate* tmpStartData = [[NSDate date] retain];//You code here...double deltaTime = [[NSDate date] timeIntervalSinceDate:tmpStartData];NSLog(@">>>>>>>>>>cost time = %f ms", deltaTime*1000);

第二种方法同样精确！！！！！！！