Re: upper limit on retain count

FROM : John Stiles
DATE : Tue Apr 19 17:45:10 2005

You know, the computer only has 4 billion bytes of memory, and even the 
most trivial of objects is 8 bytes (it needs an isa and a refcount).
FWIW, to answer the original question:
- refcounts are 32-bit ints
- I am not 100% sure, but I believe they cap at 4 billion (as opposed 
to overflowing)

At any rate, just the process of trying to retain an object billions of 
times is going to take a whole lot of CPU time, so it's probably best 
to avoid it.
It *is* possible to make objects that can be released over and over 
again without ever being freed. This might make your life easier. (I 
think you override the class and make -retainCount return UINT_MAX.)


On Apr 18, 2005, at 10:05 PM, Daniel Jalkut wrote:

> This is an interesting question, but I think you need to ask yourself 
> a question. When you get to the point where you're clearly pushing the 
> limits of a system's design, maybe you be doing it another way?
>
> I would be suspicious of any design that requires an object to be 
> retained by billions of other objects.  Is it possible that your 
> "ownership" model is such that the billion objects can contain an 
> unretained reference instead of a retained one?  If this is a 
> situation where objects need to "back-reference" container or owner 
> objects, then it often makes sense to make those references unretained 
> to avoid circular ownership problems.
>
> It seems unlikely that a billion objects could all have a legitimate 
> claim of ownership over an object within one iteration of the run 
> loop.  Maybe you can elaborate on your situation if you think it's 
> well warranted...
>
> Daniel
>
> On Apr 18, 2005, at 1:43 PM, Ivan S. Kourtev wrote:
>

>> Hello,
>>
>> I wasn't able to find any documented upper limits on retain count on 
>> 32-bit machines (or in general).  I am interested in knowing this 
>> because I foresee a situation where I may have objects with retain 
>> counts of hundreds of millions of billions and more.  So the two 
>> questions I have are:
>>
>> (1) is there a documented limit to the retain count?
>> (2) is there a documented behavior once the retain count max is 
>> reached?
>>
>> Thanks,
>>
>> --
>> ivan
>>
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