Re: [boost] [iterator] huge differences in compile time between iterator_facade and iterator helpers

From: Thomas Witt (witt_at_[hidden])
Date: 2005-10-26 11:53:23

Joaquín Mª López Muñoz wrote:
> 
> MSVC++ 6.0:
>   iterator_facade: ~7 sec.
>   bidirectional_iterator_helper: less than 1 sec.
> GCC 3.2
>   iterator_facade: 4.9 sec.
>   bidirectional_iterator_helper: 2.5 sec.

FWIW my results with gcc4 on darwin are in line with what you see from 
gcc 3.2

> 
> My questions:
> 1. Maybe the test program is flawed and has some (unseen by me)
> bias in favor of bidirectional_iterator_helper?

Well it is certainly biased in that it is simple ;-).

> 2. If not so, why is iterator_facade so very expensive? Is there
> any way to alleviate the problem?

iterator_facade covers more ground than the iterator helpers. 
Forinstance it deals with new iterator categories and iterators that 
don't fit the C++03 categories well. That being said as long as you 
don't need this functionality ...

There is a chance of a future revision of facade improving compile 
times. But this won't happen any time soon.

> 
> As it stands, I'm not so sure it's a good idea to adopt
> boost::iterator_facade:

To be honest I don't know either. As long as you don't need the extended 
functionality of iterator_facade you might be better of staying with the 
helpers for now.

HTH

Thomas

-- 
Thomas Witt
witt_at_[hidden]