[Computer-go] Kas Cup - results and prizes

Francois van Niekerk flash.slash at gmail.com
Sat Aug 11 00:59:00 PDT 2012

I did exactly this experiment with Oakfoam and I termed the potential
loss of strength, given a fixed number of playouts and a different
amount of parallel hardware, the "parallel effect." You can look at my
work on parallelisation here:
http://leafcloud.com/publications/mcts-parallelisation/ and

I found that while root parallelisation can scale well, it was not
close to the scaling of tree parallelisation for multi-core systems.
Francois van Niekerk
Email: flash.slash at gmail.com | Twitter: @francoisvn
Cell: +2784 0350 214 | Website: http://leafcloud.com

On Sat, Aug 11, 2012 at 9:46 AM, David Fotland <fotland at smart-games.com> wrote:
> I'm happy with MFGO's scaling.  I'm running a scaling test now, 4 threads vs
> 8 threads, fixed 32K total playouts per move, 19x19, no pondering.  Ideally
> the win rate should be 50%, since the total playouts are the same.  Has
> anyone tried this kind of scaling experiment, and is willing to share
> results?
> David
>> -----Original Message-----
>> From: computer-go-bounces at dvandva.org [mailto:computer-go-
>> bounces at dvandva.org] On Behalf Of Petr Baudis
>> Sent: Friday, August 10, 2012 12:47 PM
>> To: computer-go at dvandva.org
>> Subject: Re: [Computer-go] Kas Cup - results and prizes
>> On Fri, Aug 10, 2012 at 09:26:31AM -0700, David Fotland wrote:
>> > Because my current approach seems to work just as well (or maybe
>> > better), and I haven't had time to code up a shared try and tune it up
>> > to validate that assumption.  Chaslot's paper indicates perhaps that
>> > not having a shared tree is stronger.  My guess is that they are about
>> > the same, so it's not worth the effort to change.
>> In Pachi, having a shared tree makes all the difference when scaling up
>> to more threads. See the graph (really awful one, sorry, it's old!) at
>>       http://pachi.or.cz/root-vs-shared.png
>> If you have some information sharing near the root, I imagine it might
>> be similar to Pachi's distributed engine performance (or just slightly
>> better). But that is still far behind in scaling compared to the shared
>> tree in our experience.
>> P.S.: There are two important things, virtual loss (not necessarily 1
>> simulation but possibly more) and mainly lockless updates. The latter
>> also means that sane code should be really easy to modify to use single
>> shared tree instead of multiple trees.
>>                               Petr "Pasky" Baudis
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