Re: [boost] [xint] Third release is ready, requesting preliminary review

Subject: Re: [boost] [xint] Third release is ready, requesting preliminary review
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2010-05-03 08:28:13

Christopher Jefferson wrote:
> On 3 May 2010, at 12:39, Stewart, Robert wrote:
> > Chad Nelson wrote:
> >>
> >> algorithms that have to start with a copy of one or more of the
> >> passed-in parameters, but then need to modify it/them. The division
> >> algorithm requires this, just as one example off the top
> >> of my head.
> >
> > If your algorithm requires a copy, then COW should make it
> > slower because it will first manipulate the reference count
> > and because you must query in each mutating operation whether
> > to make a unique copy.
>
> But, you save the cost of copying a large object. COW has
> many disadvantages, but how can you claim it is slower when
> you require a copy?

Did you miss the "but then need to modify it/them" part?  The only reason for the copy was to have a mutable copy.  Thus, the COW overhead was useless in that example.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer, Core Software      using std::disclaimer;
Susquehanna International Group, LLP  http://www.sig.com

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