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

From: Alexander Gutenev (gutenev_at_[hidden])
Date: 2008-07-31 15:22:41

> 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

It depends, I think. Assume shared_ptr is used as an easy way to deal with 
polymorphic objects, like putting them into std::vector. Then most of the 
pointers would be unique. So vector data size is doubled, but this is not 
the most overhead. The most overhead is counter and deleter objects, those 
objects are larger than a single pointer, and each of them is stored in 
dedicated heap block.
If shared_ptr is used really to share objects, then doubling pointer size 
may cause more overhead than counter and deleter.