Xcode has excellent instrumentation tools for profiling your code. But sometimes you want to compare the performance of 2 versions of the same code performing the same task. Here's a bit of code I use to print out how long it takes to run a block of code:

void moTime1(void(^block)(void), NSString* s) {
    NSDate* start = [NSDate date];
    block();
    NSLog(@"%@ %f", s, [[NSDate date] timeIntervalSinceDate:start]);
}

Here's how you use it to compare the performance of 2 pieces of code:

moTime1(^{
    runVersion1();
}, @"version 1");

moTime1(^{
    runVersion2();
}, @"version 2");

And it should print something like:

> version 1 0.100000
> version 2 0.001000

While not terribly accurate, you can see at a glance that version 2 is 2 orders of magnitude faster.

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