application crash after low memory warnings - iphone

Question

my iphone application crash after raising 4 warnings of low memory, instruments is showing no memory leaks but in memory allocation live Bytes goes up to 4.7mb and Over all Bytes goes upto 79.0 MB and application crash at this point
any help will be highly appreciated
for (int i = 0; i<3; i++)
{
UIImage *rendered_image;
UIGraphicsBeginImageContextWithOptions(sub_view.bounds.size, NO, 0.0);
[appdelegate.arrimages removeAllObjects];
[appdelegate.arranimations removeAllObjects];
NSString *oldgroup = [[NSString alloc] init];
NSString *currentgroup = [[NSString alloc] init];
for(int i=0; i<[sub_view.data count]; i++)
{
oldgroup = (i>0) ? [sub_view.group objectAtIndex:(i-1)] : [sub_view.group objectAtIndex:i];
currentgroup = [sub_view.group objectAtIndex:i];
/*
IF DIFFERENT GROUP NAME RECEIVED
1-GET NEW INSTANCE OF IMAGE
2-SAVE PREVIOUS IN ARRAY
*/
if (![oldgroup isEqualToString:currentgroup])
{
rendered_image = UIGraphicsGetImageFromCurrentImageContext();
[self SaveImagesOfAnimation:[self compressImageDownToPhoneScreenSize:rendered_image]];
[appdelegate.arranimations addObject:[sub_view.anim objectAtIndex:i]];
UIGraphicsEndImageContext();
UIGraphicsBeginImageContextWithOptions(sub_view.bounds.size, NO, 0.0);
}
id element = [sub_view.data objectAtIndex:i];
color = [sub_view.fillColor objectAtIndex:i];
[color setFill];
[element fill];
[[UIColor blackColor] setStroke];
[element stroke];
}
rendered_image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
[self SaveImagesOfAnimation:[self compressImageDownToPhoneScreenSize:rendered_image]];
}

Answer 1

Increasing memory use without a leak implies that you're storing data that you never release, and you're still holding a reference to it.
This usually means that one of the data structures that will grow automatically when you put more data in it, like NSMutableArray, is to blame. They will happily hold all the data you add to them and the memory profiler won't find any leaks since items put in the NSMutableArray are - by definition - never released and not detected as leaks since there's a reference to them from the array.
Edit: For the general way to solve this if you have no obvious places to look, see the comment from #Costique at the top;
Instruments can also show the kind of objects you've allocated and
the exact stack traces, so you should be able to quickly figure it
out.