On Monday 21 April 2008 14:11:51 Richard Jones wrote:
> On Mon, Apr 21, 2008 at 02:27:36PM +0200, Berke Durak wrote:
> > On Mon, Apr 21, 2008 at 1:17 PM, Jon Harrop <jon@ffconsultancy.com> wrote:
> > > Quad cores are already the norm.
> > >
> > > An *eight* core Dell Precision T7400 now costs only £1,171. Our desktop
> > > machines will be replaced with these eight core machines before the end
> > > of this year.
> >
> > Well it's worse than what I thought then.
>
> Your threaded code is going to look really stupid when you have NUMA
> machines with dozens of cores.  Why are we optimizing for a case (SMP)
> which will only be around for a few years.  Arguably SMP isn't even
> around now ... the AMD machine on which I'm typing this is firmly NUMA
> with a good 10% penalty for accessing memory owned by the other
> socket.

10% is nothing compared to the orders of magnitude cost of message passing.

> > A concurrent GC should be developed.  But I think you can compete in
> > some "niches" without a concurrent GC.
>
> Why should a concurrent GC be developed?  Threaded code is a nightmare
> to write & debug, and it's only convenient for lazy programmers who
> can't be bothered to think in advance about how they want to share
> data.  OCaml supports fork, event channels & shared memory right now
> (and has done for years) so there is no penalty to writing it
> properly.

Ten years ago that was:

  "Why should we use gargage collection? Garbage collectors are a nightmare to 
implement and debug and are only useful for lazy programmers who cannot be 
bothered to deallocate values themselves. C++ has reference counting right 
now and there is no penalty for using it properly."

-- 
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
http://www.ffconsultancy.com/products/?e