> have you evaluated the improvement of strength on your 40-core pc cluster?
I already published a scalability analysis of Pachi on a single machine: http://comments.gmane.org/gmane.games.devel.go/20925 I wrote the multi-machine (message passing) code for Pachi. It uses slow tree parallelization as described in http://hal.inria.fr/inria-00512854/ On a single machine doubling the number of playouts gains approximately 100 elo and I did not observe reduced scalability at high number of playouts. On multiple machines, a doubling gains approximately 50 elo initially, but scalability quickly drops to a point where increasing the number of machines doesn't improve strength and can actually reduce it. This is consistent with the observations of the above paper inria-00512854. This analysis was done with a constant opponent (Fuego running on a single machine with 7 cores) in 19x19. 3662 games were played in total. pachi was running on up to 40 machines using 7 cores each. This is not Petr's cluster, but Petr also measured roughly 50 elo per initial doubling on his cluster. In practice pachi cannot currently make good use of more than 10 machines. I'm confident that over time we will learn how to push scalability further, but this will require new algorithmic insights. [image: pachi-scalability.png] Jean-loup
<<pachi-scalability.png>>
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