Re: [Boost-Users] Threads and Smart Ptrs

From: Peter Dimov (pdimov_at_[hidden])
Date: 2002-02-16 14:09:08

From: "Colin Fox" <cfox_at_[hidden]>
> On Sat, 2002-02-16 at 10:50, Peter Dimov wrote:
> > From: "Colin Fox" <cfox_at_[hidden]>
> > > I got the CVS version of boost, which you suggested, and had my
program
> > > running all night last night. No problems so far. Perhaps this solves
> > > it.
> >
> > Let's hope so. I presume you're on a multiprocessor? Could you please
also
> > try my latest attempt, that uses lwm_linux.hpp on linux instead of the
> > generic lwm_pthreads.hpp? It's much faster than the pthreads version
when
> > there's no contention but there's no point being faster if it's
incorrect.
>
> Yes, I forgot to mention that - I'm developing on a dual processor box.

I kind of suspected that. This probably means that the atomic_* functions
don't synchronize memory (they are supposed to, but...)

> How do I try the latest attempt? Is that what's in CVS, or do I need
> something else?

Yes, it's in CVS. I've also added a test for thread safety,
libs/smart_ptr/shared_ptr_mt_test.cpp.

> Speed will become important, because eventually this is going to have to
> handle a fairly high thread & activity load. But I completely agree that
> correctness comes first. :)

Copying a shared_ptr is about 3.4 times faster with the specialized version,
but it depends on atomic_inc and atomic_dec_and_test as well, so it probably
won't work. Oh well.