Subj : Re: A question about atomic_ptr
To   : comp.programming.threads
From : Joe Seigh
Date : Wed Apr 13 2005 02:38 pm

On Wed, 13 Apr 2005 18:53:50 +0300, Peter Dimov <pdimov@gmail.com> wrote:

> Joe Seigh wrote:
>
>> atomic_ptr/local_ptr is a modified weighted reference counting
>> scheme.  local_ptr looks a lot like pure weighted reference counting.
>
> From looking at the source, local_ptr doesn't seem weighted to me. There is
> no weight member and copies just increment a shared reference count (the
> ephemeral count). But maybe I'm not looking at the latest version (the one
> on atomic-ptr-plus.sf.net is 0.0.2).
>
Copying an atomic_ptr to a local ptr is a tranfer of 1 weighted reference
count without updating the central reference count.  local_ptr orginally
weren't copyable since they only have a weight of 1 but I added some logic
 from atomic_ptr to atomic_ptr copying, it's just not as efficient.  The
extra logic obfuscates the weighted ptr logic somewhat so it's hard to
see.

-- 
Joe Seigh

.