High resolution timing in Cocoa

Note: This blog is deprecated. @synthesize zach has moved to a new home, at zpasternack.org. This blog entry can be found on the new blog here. Please update your links.

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For profiling app performance, it's necessary to accurately time your code. The best way to do this is to use mach_absolute_time. In conjunction with mach_timebase_info, you can get extremely high resolution timing to ease performance benchmarking.

I've wrapped this functionality up in a little class to make it super easy to use.

// MachTimer.h
#include <mach/mach_time.h>

@interface MachTimer : NSObject
{
    uint64_t timeZero;
}

+ (id) timer;

- (void) start;
- (uint64_t) elapsed;
- (float) elapsedSeconds;
@end

// MachTimer.m
#import "MachTimer.h"

static mach_timebase_info_data_t timeBase;

@implementation MachTimer

+ (void) initialize
{
    (void) mach_timebase_info( &timeBase );
}

+ (id) timer
{
#if( __has_feature( objc_arc ) )
    return [[[self class] alloc] init];
#else
    return [[[[self class] alloc] init] autorelease];
#endif
}

- (id) init
{
    if( (self = [super init]) ) {
        timeZero = mach_absolute_time();
    }
    return self;
}

- (void) start
{
    timeZero = mach_absolute_time();
}

- (uint64_t) elapsed
{
    return mach_absolute_time() - timeZero;
}

- (float) elapsedSeconds
{
    return ((float)(mach_absolute_time() - timeZero)) 
        * ((float)timeBase.numer) / ((float)timeBase.denom) / 1000000000.0f;
}

@end

You'd use it like this:

MachTimer* aTimer = [MachTimer timer];
[self performSomeOperation];
NSLog( @"performSomeOperation took %f seconds", [aTimer elapsedSeconds] );

I've used this code for iOS and Mac OS apps, and it works great.