RE: [computer-go] Scalability Odd-Even Effect

["David Fotland" <fotland@xxxxxxxxxxxxxxx>]

Quiescence search is really important in go.  many Faces spends almost all
of its full board search in quiescence.

David

> -----Original Message-----
> From: computer-go-bounces@xxxxxxxxxxxxxxxxx 
> [mailto:computer-go-bounces@xxxxxxxxxxxxxxxxx] On Behalf Of chrilly
> Sent: Tuesday, January 18, 2005 7:48 AM
> To: computer-go
> Subject: Re: [computer-go] Scalability Odd-Even Effect
> 
> 
> With my evaluation function there was a strong effect of 
> odd/even search depth. With odd depth the program would play 
> unreasonable moves (because it could always play some 
> unreasonable attack as the last move).
> 
> Interesting. With a quiesence search it is the other way 
> round. Usually the moves at odd depths are more reasonable. 
> At least when the search is not too deep and the search tree 
> is relatively balanced. At very deep searches (e.g. Hydra 
> searches typically to depth 17-18) the effect disappears. 
> There are many extensions and selective pruning and the end 
> of the line is in many case not at the nominal search-depth.
> 
> I think that finding reasonable and efficient quiesence rules 
> is a very critical topic for using a chess-like search in Go. 
> In Chess it is relative trivial.  But the chess programm Bebe 
> had no quiesence at all. Bebe searched in 2 ply steps. I 
> experimented also in Hydra to skip the quiescence search. It 
> does not work too badly. The evaluation is relative 
> sophisticated and the search was surprisingly stable. But it 
> was less efficient than with a quiescence. Typically the 
> search with quiescence recogized tactical wins/losses 1-2 
> Plies earlier. The overhead for the quiesence is typical a 
> factor of 2. 1-2 Plies additional lookahead is worth appr. a factor 5.
> 
> The stability of the search is probably also related with the 
> deep search. Forcing lines are even extended further and a 
> lot of tactical instabilities are therefore already resolved 
> within the search tree.
> 
> Chrilly
> 
> 
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