Re: limiting CPU usage

FROM : Murat Konar
DATE : Fri Nov 30 22:07:33 2007

On Nov 30, 2007, at 12:19 PM, Alexander Cohen wrote:

> What im doing is pretty simple. I have a loop that for each 
> iteration, opens an image, gets some info, then closes it down 
> ( using CG of course ). Everything is released correctly and there 
> are no leaks. BUt after a while, the system gets unresponsive.


But *when* are things being released?

A common problem when running in a loop is that objects that are 
autoreleased (so-called temporary objects) aren't actually 
deallocated until the end of the current run-loop. Often, these 
temporary objects aren't ones you've created; they're created as a 
side effect of code that you're calling.

You can avoid the build-up of temporary objects by using your own 
auto-release pool thusly (typed in Mail, this is just pseudo code to 
illustrate the concept):

NSAutoreleasePool * autoreleasePool = [[NSAutoreleasePool alloc]init];

while (keepLooping)
{
    do stuff...

    if (number of loops since the last time we released the 
autoreleasePool is above some threshold)
    {
        [autoreleasePool release];
        autoreleasePool = [[NSAutoreleasePool alloc]init];
    }
}

[autoreleasePool release];


How often you release the autorelease pool depends on how memory 
heavy your operations are.

_murat