How to improve NSDictionary's performance

I've got a lot of objects, every one has some tags, which are stored in NSDictionary. I've also got a loop, in which I'm iterating through all objects and do some stuff depending on object's tags. Method objectForKey: worsens performance a lot, if there are too many calls of it. How can I improve the performance? I've tried, for example, set "strong" instead of "copy" into @property, but that did not solve problem. Thanks!

EDITED:

Here is some kind of code, it is much more simple than the one in my project, of course. The Profiler says that the hot spots are in objectForKey:, not in doSomeStuff:. Can It be because of amount of its calls? Tags have got few objects, about 10 for each object, but the amount of objects is rather large

.h:

@interface MyObject : NSObject
 
 @property (nonatomic, readwrite, strong/*copy*/  ) NSDictionary *tags;
 
 -(void)doSomeStuff;
 
 @end
 

.m:

@implementation MyObject
 {
     NSDictionary *tags; // about 10 values for each object
 }
 
 @synthesize map;
 
 -(NSDictionary *)tags
 {
     return tags;
 }
 
 -(void)setTags:(NSDictionary *)newTags
 {
     tags = [newTags copy];
 }
 
 -(void)doSomeStuff;
 
 @end
 

using:

NSArray *objects = ... // a lot of items, > 1000
 NSArray *rules = ... // NSArray of objects with property NSArray* Strings, about 50 strings
 
 for (MyObject *object in objects)
 {
     for (NSArray *rule in rules)
     {
         for (NSString *ruleString in rule.Strings)
         {
             // there is a more complicated check in my project, so you may imagine that there are 10 calls of objectForKey:, with different keys
             if ([object objectForKey:ruleString] isEqualToString:@"yes"])
             {
                 [object doSomeStuff];
             }
         }
     }
 }
 

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