Rudimentary ways to measure execution time of a method

Question

What object/method would I call to get current time in milliseconds (or great precision) to help measure how long a method took to execute?

NSDate's timeIntervalSinceDate will return NSInterval which is measured in seconds. I am looking for something finer grained, something similar to Java's System.currentTimeMillis.

Is there an equivalent version in objective-c/CocoaTouch?

Answer 1

For very fine-grained timings on OS X, I use mach_absolute_time( ), which is defined in <mach/mach_time.h>. You can use it as follows:

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

static double ticksToNanoseconds = 0.0;

uint64_t startTime = mach_absolute_time( );
// Do some stuff you want to time here
uint64_t endTime = mach_absolute_time( );

 // Elapsed time in mach time units
uint64_t elapsedTime = endTime - startTime;

// The first time we get here, ask the system
// how to convert mach time units to nanoseconds
if (0.0 == ticksToNanoseconds) {
    mach_timebase_info_data_t timebase;
    // to be completely pedantic, check the return code of this next call.
    mach_timebase_info(&timebase);
    ticksToNanoseconds = (double)timebase.numer / timebase.denom;
}

double elapsedTimeInNanoseconds = elapsedTime * ticksToNanoseconds;