Re: Objective-C and Smalltalk; speed of message send

[Adrian Robert]

On Aug 18, 2004, at 3:49 PM, Marcel Weiher wrote:

> Whoa, an NSDictionary is a pretty heavy-weight item, especially 
> compared to a simple 2D array!  Why not stick with the 2D array, if I 
> may ask?  After all, one of the point of Objective-C is that it *is* 
> C.
>
> >  We decided to use NSStrings as the keys.
>
> Also potentially fairly heavy, though a common choice.  I remember 
> people complaining about NSString's performance compared to char* when 
> Foundation was introduced.  However, NSString is really for "human 
> readable" text, whereas char* is often more for "tokens", or really 
> just byte-sequences.
>
> >  To maintain a backwards bridge, we took the old 2D access indices 
> > and turned them into a string. And then stored/set them in the 
> > NSMutableDictionary via those. The performance was not impressive.
>
> I wouldn't expect it to be.  NS(Mutable)Dictionary is pretty slow.  
> One issue is that it copies its keys.  Arrrggghh.

While it's good to have the raw C capabilities there for extreme cases, 
it's NOT much good having a nice, high-level API if it's so slow you 
end up dropping back to mid-level C (with all of its tedium and 
error-proneness) much of the time.  I'm going to get in trouble here 
for talking instead of sending code ;), but it seems like the class 
NSString and at least the plist classes NSDictionary and NSArray ought 
to be as optimized as well as they can possibly be.  These are used 
everywhere in the libraries and in applications, and effort in this 
direction should pay off handsomely.  I'm sure much has been done 
already, but perhaps there is still some reasonably low-hanging fruit 
remaining?

I realize there are things that just have to be done for correct 
behavior (e.g., hash key copying), but I just don't see how any 
Smalltalk environment should be able to match Objective-C in 
performance for a straightforward application of strings and 
dictionaries.  We ought to look at these implementations (if any have 
source available) and see what techniques they are using.