I think this is?one of those?design decisions that nobody takes on faith. We all wind up testing it both ways and in various combinations.
An additional advantage of using the number of visits is that branches at the root become mathematically eliminated and can be pruned away. It often also allows the search to be stopped early. It can save a lot of time for forced moves. - Dave Hillis -----Original Message----- From: Michael Williams <michaelwilliam...@gmail.com> To: computer-go <computer-go@computer-go.org> Sent: Sat, 6 Jun 2009 5:07 pm Subject: Re: [computer-go] Tweak to MCTS selection criterion Another strategy to be considered is to not allow the thinking to cease until the maximum win rate and the maximum visit count agree on the same move. Obviously this requires some extra code to make sure you don't lose on time, etc.? ? Brian Sheppard wrote:? > When a UCT search is completed, the usual selection criterion is? > "choose the move that has the most trials." This is more stable? > than choosing the move that has the highest percentage of wins,? > since it is possible to have an unreliably high percentage if the? > number of trials is small.? > > I have a small tweak to that criterion. Pebbles uses "choose the? > move that has the most wins." This rule selects the same move as? > the conventional criterion in almost every case. The reason why? > Pebbles' rule is superior is revealed in the case where the moves? > differ.? > > When Pebbles chooses a different move than the conventional criterion,? > it is because Pebbles move has more wins in fewer trials. When that? > happens, Pebbles move would inevitably become the move with the most? > trials if searching were to continue. So there is actually no downside.? > Of course, the upside is minor, too.? > > For validation, Pebbles has been using both strategies on CGOS games.? > At present, the conventional selection strategy has won 341/498 = 68.47%.? > Pebbles strategy has won 415/583 = 71.18%. This isn't statistically? > conclusive or anything (0.7 standard deviations; we would need 4 to 8? > times as many trials for strong statistical evidence). But Pebbles'? > strategy should be better by a small amount, and it has been, so I? > present it to you with confidence.? > > Best,? > Brian? > > _______________________________________________? > computer-go mailing list? > computer...@computer-go.org? > http://www.computer-go.org/mailman/listinfo/computer-go/? > ? _______________________________________________? computer-go mailing list? computer...@computer-go.org? http://www.computer-go.org/mailman/listinfo/computer-go/?
_______________________________________________ computer-go mailing list computer-go@computer-go.org http://www.computer-go.org/mailman/listinfo/computer-go/
