ARC vs MRC（従来のretain/release）に関するベンチマークと考察。
様々な速度比較が行われているがほとんど差は無い。
ARCが遅くなると思われるケース
// this is typical MRC code:
{
id object = [array objectAtIndex:0];
[object doSomething];
[object doAnotherThing];
}
// this is what ARC does (and what is considered best practice under MRC):
{
id object = [array objectAtIndex:0];
[object retain]; // inserted by ARC
[object doSomething];
[object doAnotherThing];
[object release]; // inserted by ARC
}// this is typical MRC code:
-(void) someMethod:(id)object
{
[object doSomething];
[object doAnotherThing];
}
// this is what ARC does (and what is considered best practice under MRC):
-(void) someMethod:(id)object
{
[object retain]; // inserted by ARC
[object doSomething];
[object doAnotherThing];
[object release]; // inserted by ARC
}
最後はそんなに速度が気になるならCで書けよ、みたいな（それを言ったら見も蓋もないが..）。