Re: [Boost-users] [intrusive_ptr] Counting implementation

From: Gennadiy Rozental (rogeeff_at_[hidden])
Date: 2008-07-31 12:51:50

Alexander <gutenev <at> gmail.com> writes:

> 
> > On Wednesday 30 July 2008 16:03 pm, Alexander Gutenev wrote:
> >> I want to use intrusive_ptr as a smart pointer to have reference counting
> >> without shared_ptr overhead.
> >
> > I'm curious, could you be more specific about how your implementation has 
> > less
> > overhead than shared_ptr?  Do you mean it uses less memory?  Compiles 
> > faster?
> > Runs faster?
> 
> Less memory.
> The overhead of shared_ptr is allocation of another object which has 
> reference count and deleter object. It is allocated in a separate block, 
> hence memory overhead - that's the most noticeable when I have a lot of 
> pointers to small objects.

You confuse thing a bit I believe. The over head is not caused so much by the
extra object itself as by the pointer to this object that have to reside inside
every shared_ptr doubling it's size effectively.

Gennadiy