ordered sets operations on lists..

[Steve Holden]

Felipe Almeida Lessa wrote:
> Em Dom, 2006-02-12 às 23:51 -0500, Steve Holden escreveu:
> 
>>The basic answer is that so far no developer has felt it worthwhile to 
>>expend time on adding these optimizations.
> 
> 
> I always thought these small optimizations could lead Python to be
> faster overall. I remember about this every time I see CPython vs.
> IronPython benchmarks (.NET and Mono do some nice optimizations at
> compile and run times).
> 
Indeed it is true that on some benchmarks IronPython is faster than 
CPython. I suspect this was helped by the fact that IronPython is Jim's 
third implementation of Python (I believe he was familiar with CPython 
before he started on Jython, formerly known as JPython).

The fact remains that until someone writes the code it can't be included 
in the implementation. Performance optimization, unfortunately, doesn't 
have the same glamorous cachet as more esoteric language features.
> 
>>>Also, IIRC Psyco does optimize these constant expressions. Or am I
>>>wrong?
>>>
>>
>>Psyco does some very advanced things, but it does them all at run-time. 
>>Unless I misunderstand (not unheard of), there are no circumstances 
>>under which Psyco will improve run-time for a piece of code that is only 
>>executed once.
> 
> 
> Sorry, I think I should have been clearer. Yes, Psyco only helps at
> runtime (when the function is called), but those constant folds only
> practically help on parts of the code that are called many times anyway,
> right?
> 
Right. Technically constant folding is a win for a single execution, but 
only if you don't take the slightly-increased compile time into account :-)

regards
  Steve
-- 
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