Optimize function with creating NSDictionarry - ios

Question

I am trying to optimize function which returns NSMutableDictionary like this :
-(NSMutableDictionary *)getValuses{
NSNumber *n1 = [NSNumber numberWithInt:-1];
NSNumber *n2 = [NSNumber numberWithInt:-1];
NSNumber *n3 = [NSNumber numberWithInt:-1];
NSNumber *n4 = [NSNumber numberWithInt:-1];
NSNumber *n5 = [NSNumber numberWithInt:-1];
if (self.k1)
n1 = self.k1;
if (self.k2)
n2 = self.k2;
if (self.k3)
n3 = self.k3;
if (self.k4)
n4 = self.k4;
if (self.k5)
n5 = self.k5;
NSMutableDictionary * dictionary = [[NSMutableDictionary alloc]initWithObjectsAndKeys:n1,[NSNumber numberWithInt:2],n2,[NSNumber numberWithInt:3],n3,[NSNumber numberWithInt:4],n4,[NSNumber numberWithInt:5],n5,[NSNumber numberWithInt:6], nil];
return dictionary;
}
I run this function in loop more than 1 000 000 times, so any optimisation is good. It works but I want it to work significantly faster.

Answer 1

do you really need dictionnary with -1 values ?
you can avoid all the "if/then" stuff (I heard it can be quite slow for a cpu) if you just do
NSMutableDictionary * dictionary = [[NSMutableDictionary alloc]initWithObjectsAndKeys:k1,[NSNumber numberWithInt:2],k2,[NSNumber numberWithInt:3],k3,[NSNumber numberWithInt:4],k4,[NSNumber numberWithInt:5],k5,[NSNumber numberWithInt:6], nil];
// then you can do things like this
id obj = [dictionary objectForKey:#2];
if (obj)
NSLog(#"dict with good values");
else
NSLog(#"old dict with -1");

Answer 2

-(NSMutableDictionary *)getValuses{
NSNumber *n1 = [NSNumber numberWithInt:-1];
NSMutableDictionary * dictionary = [[NSMutableDictionary alloc]initWithObjectsAndKeys:(self.k1)? self.k1:n1,[NSNumber numberWithInt:2],(self.k2)? self.k2:n1,[NSNumber numberWithInt:3],(self.k3)? self.k3:n1,[NSNumber numberWithInt:4],(self.k4)? self.k4:n1,[NSNumber numberWithInt:5],(self.k5)? self.k5:n1,[NSNumber numberWithInt:6], nil];
return dictionary;
}
try the above code....

Answer 3

You can try something like this (not tested):
-(NSMutableDictionary *)getValuses {
NSNumber *n = [NSNumber numberWithInt:-1];
NSMutableDictionary * dictionary =
[[NSMutableDictionary alloc] initWithObjectsAndKeys:
self.k1 ? self.k1 : n,[NSNumber numberWithInt:2],
self.k2 ? self.k2 : n,[NSNumber numberWithInt:3]...
return dictionary;
}

Answer 4

You can reduce the number of NSNumber objects created, and you can use the new literal syntax to at least make the code shorter & easier to read. You can also halve the number of property accesses. Whether any of this will have a big impact on performance you'll have to find out.
-(NSMutableDictionary *)getValuses
{
NSNumber *n = #(-1);
return #{ #2: (self.k1 ?: n), #3: (self.k2 ?: n), #4: (self.k3 ?: n),
#5: (self.k4 ?: n), #6: (self.k5 ?: n)
};
}
(The expression a ?: b is shorthand for a ? a : b but a will only be evaluated once, hence the halving of the number of property accesses.)

Answer 5

Try this! dispatch_appy method is for create loops and execute the code inside in concurrent queues. This is a better way of executing big loops.
dispatch_apply blocks - Apple Documentation
I didn't compile it but it should work. Hope it help to give you a clue. Good luck!
-(NSMutableDictionary *)getValuses{
//add the values here
NSMutableArray *array = [#[self.k1,self.k2,self.k3,self.k4,self.k5]mutableCopy];
NSMutableDictionary * dictionary = [#{}mutableCopy];
//this kind of block is better for big loops...
size_t count = array.count;
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_apply(count, queue, ^(size_t i) {
id value = [array objectAtIndex:i];
[dictionary setObject:value?value:(#-1) forKey:#(i)];
});
return dictionary;
}