performance analysis producer_consumer.cc TEST_T5

[Dhruv Matani]

On Tue, 2004-02-17 at 22:29, Nathan Myers wrote:
> On Tue, Feb 17, 2004 at 09:30:44AM -0700, law@redhat.com wrote:
> > In message <4030DE6D.50607@redhat.com>, Will Cohen writes:
> >  >I looked over the code a bit more. The tight loop that the code spends 
> >  >most of its time is the result of the size() operation. The code is 
> >  >counting the number of elements in the list.   ...
> >
> > Funny, a one of the customers you visited a couple weeks ago has
> > complained repeatedly about not having an efficient means to get the
> > number of objects on a list....
> 
> std::list<>::size() is linear in N because the alternative would be
> to make splicing linear.  The latter is the more commonly called in 
> a loop.  (The splice operation on lists is among the most clever and
> appealing features of the STL.  I claim credit for naming it.)
> 
> If you're very interested in the size of the container, you'll use 
> a different data structure, or keep a separate count.  Note that 
> maintaining a count is also linear in N, it's just that the cost is 
> amortized over as many times as you look at it.

Why can't the library have a configure option to determine whether the
size() function will be O(N) or not. It would be easy to provide both
versions in the library AFAIK.




-- 
	-Dhruv Matani.
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