CODEWITHSUNDEEP
iphoneobjective-ciosmemory-managementautomatic-ref-counting
Peter Kazazes
Peter Kazazes

Reputation: 3628

Memory issue or something else?

I'm running an application on my iPad that loads images into a carousel. In total there are 138 images. If I reduce that number to 100, the application loads fine. At 138, however, the application pauses, rather than crashes.

The viewDidLoad and first for statement are being reached, as indicated by a breakpoint. The issue lies in the second for statement.

    // loading images into the queue

loadImagesOperationQueue = [[NSOperationQueue alloc] init];
NSMutableArray *tmpArray = [[NSMutableArray alloc] initWithCapacity:14];

for (int i = 0; i < 137; i++) {
    [tmpArray addObject:[NSString stringWithFormat:@"cover_%d.jpg", i]];
}

for (int i = 0; i < 137; i++) {
    int index = arc4random() % [tmpArray count];
    NSString *imageName = [tmpArray objectAtIndex:index];
    [tmpArray removeObjectAtIndex:index];
    [(AFOpenFlowView *)self.view setImage:[UIImage imageNamed:imageName] forIndex:i];
}

I'm guessing that there is a memory issue, although since I'm using iOS 5 with ARC I shouldn't have to be doing any manual memory management.

Could it possibly be that there is just too much going on to hold in memory? It's 138 images @ ~146 KB per. That's roughly 20 MB, but I don't think that alone could cause the issue.

GDB quits without any useful output, actually no output at all. Running instruments reveals that when the pause takes place real memory usage is only at 6.11 MB, 77.4% CPU but 175 MB of virtual mem.

What I'm concerned about is the fact that there is no memory warning or even an actual crash, the thread just pauses and cannot be resumed or killed automatically, you have to kill it from within xcode.

Upvotes: 2

Views: 353

Answers (1)

sergio
sergio

Reputation: 69047

It looks pretty like your application gets killed because it takes too much memory. Indeed, 20MB is the limit that I have experienced, and this also corresponds to what you could find by googling it.

About the fact that you don't receive any memory warning, this happens because you are loading the images in memory in a tight loop that does not returns control to the main loop. So you don't have the chance to receive the message didReceiveMemoryWarning.

The solution is pretty simple, pre-load a number of images and as you move through the carousel, pre-load some more images, while also releasing the older ones. In reality, you don't need to have in memory more than 5 images at any time to keep the balls running. If you are concerned about not having to load the images almost each and every time, then you can increase that number.

Upvotes: 5

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