Re: [boost] [xint] Performance of fixed-size large integers

Subject: Re: [boost] [xint] Performance of fixed-size large integers
From: Ivan Le Lann (ivan.lelann_at_[hidden])
Date: 2011-03-05 07:04:40

Le samedi 05 mars 2011 à 01:43 -0800, Artyom a écrit :
> 
> 
> 
> ----- Original Message ----
> > From: Dave Abrahams <dave_at_[hidden]>
> > To: boost_at_[hidden]
> > Sent: Sat, March 5, 2011 12:21:50 AM
> > Subject: Re: [boost] [xint] Performance of fixed-size large integers
> > 
> > At Fri, 4 Mar 2011 13:58:36 -0800 (PST),
> > Artyom wrote:
> > > 
> > > I  personally think that COW approach would be very useful for most
> > > of  users while move is "nice-to-have".
> > 
> > That's interesting, but it doesn't  help me form my own opinion.  Maybe
> > if you told us on what basis you  came to that conclusion, it would be
> > more helpful.  Have you done any  tests to see how easily/quickly a
> > type implemented with move emulation works  as compared to one
> > implemented with COW?  Have you got concrete  examples?
> > 
> 
> 
> I'm not talking about performance I'm talking about what users would do.
> 
> How many developers would write:
> 
>    {
>      ...
>      foo.set_value(boost::move(some_big_int));
>      // some big int goes out of scope
>    }
> 
> Over
>   
>    {
>      ...
>      foo.set_value(some_big_int);
>      // some big int goes out of scope
>    }
> 
> In case you really need a copy of the value and not reference/const reference.
> 
> We should remember that not all Boost audience is familiar
> with "movable" concept. Even good C++ programmers
> do not really live on the edge and use the-state-of-the-art tools.
> 

The opposite view also stands: Move will benefit to most C++
classes/functions while only those who have designed their classes to
use COW can afford not to use Move. Designing a COW class is more
complex than a Move enabled one.

My KISS understanding of move is that it's telling me: use functional
programming style, so that you don't need std::move.
Of course, this is not always possible, but I think that this limits the
scope of your (valid) point.

Ivan