IOS测试程序运行耗时

iOS设备相对于电脑，内存和处理能力有限，所以一段代码或者程序运行的时间需要时刻注意，这里提供两种获取精确时间的方法。

方法一：使用系统时间

1 NSDate* tmpStartData = [[NSDate date] retain];
2 //You code here...
3 double deltaTime = [[NSDate date] timeIntervalSinceDate:tmpStartData];
4 NSLog(@">>>>>>>>>>cost time = %f ms", deltaTime*1000);

方法二：

 1 #import <mach/mach_time.h>
 2
 3 uint64_t start = mach_absolute_time();
 4 //You code here...
 5 uint64_t end = mach_absolute_time();
 6 uint64_t elapsed = end - start;mach_timebase_info_data_t info;
 7 if (mach_timebase_info (&info) != KERN_SUCCESS)
 8 {
 9     printf ("mach_timebase_info failed\n");
10 }
11 uint64_t nanosecs = elapsed * info.numer / info.denom;
12 uint64_t millisecs = nanosecs / 1000000;
13 NSLog(@">>>>>>>>>>cost time = %ld ms", millisecs);