[Computer-go] Kas Cup - results and prizes

Jean-loup Gailly jloup at gailly.net
Tue Aug 14 12:08:42 PDT 2012


> I understand how you update the counters lock-free, but
> surely you must have a lock to protect adding a new node to the tree?

We have a single atomic test-and-set instruction to expand a node (add
only once. It is not a blocking mutex. If a thread finds that the node is
not yet expanded but some other thread is already allocating new children,
it simply
goes on, starting a playout at this point.

> Do this impact scaling at some point?

Maybe above 24 cores, but we couldn't measure this. Pachi scales perfectly
up to 24 cores
in single-machine mode. See the reference given by Pasky earlier in this
Fig. 9 of http://pasky.or.cz/go/pachi-tr.pdf

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