"two hyperthreads SHARE some of the same hardware"
On Sat, Aug 11, 2012 at 9:34 PM, Michael Williams <[email protected]> wrote: > Because two hyperthreads some of the same hardware. And some of that > hardware is required to do the spinning. Just a thought. > > Found this with a quick search: > http://archives.postgresql.org/pgsql-patches/2003-12/msg00345.php > > > On Sat, Aug 11, 2012 at 8:45 PM, Hideki Kato <[email protected]> wrote: >> Michael Williams: >> <CAB0EdYWgs=gjsnt9rmkj8-utlg72nyxnafvd-8iq_pjjf_j...@mail.gmail.com>: >>>I wonder if spin-lock hurts hyperthreading. >> >> Why do you think so? If a spin-lock accesses memory and waits, >> simply another thread runs. That's all. >> >> Hideki >> >>>On Sat, Aug 11, 2012 at 7:22 PM, Hideki Kato <[email protected]> wrote: >>>> Petr Baudis: <[email protected]>: >>>>>On Sat, Aug 11, 2012 at 12:52:12AM -0700, David Fotland wrote: >>>>>> Yes, root parallelization with some sharing. >>>>>> http://www.personeel.unimaas.nl/G-Chaslot/papers/parallelMCTS.pdf said it >>>>>> was good and I tried it and it works well. >>>>> >>>>>The paper is not so relevant now, since the standard method of most >>>>>programs is lockless tree parallelization, which is not covered. >>>>>The locking overhead is quite significant, I'd expect, as locking >>>>>instructions can AFAIK take hundreds of cycles. >>>> >>>> With spin-lock or hardware test-and-set instructions, locking overhead >>>> is very small. >>>> >>>>>That said, root parallelization overperforming sequential simulations >>>>>is something I never managed to reproduce and that seems rather >>>>>surprising to me. It might have something to do with the way priors >>>>>are done in the tree or some other engine-specific factors. >>>> >>>> I believe IBM Power processor's architecture may caused the super-linear >>>> acceralaton. >>>> >>>> Hideki >>>> -- >>>> Hideki Kato <mailto:[email protected]> >>>> _______________________________________________ >>>> Computer-go mailing list >>>> [email protected] >>>> http://dvandva.org/cgi-bin/mailman/listinfo/computer-go >>>_______________________________________________ >>>Computer-go mailing list >>>[email protected] >>>http://dvandva.org/cgi-bin/mailman/listinfo/computer-go >> -- >> Hideki Kato <mailto:[email protected]> >> _______________________________________________ >> Computer-go mailing list >> [email protected] >> http://dvandva.org/cgi-bin/mailman/listinfo/computer-go _______________________________________________ Computer-go mailing list [email protected] http://dvandva.org/cgi-bin/mailman/listinfo/computer-go
