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Subject: Re: High branching factor games

Author: Uri Blass

Date: 02:23:56 11/27/02

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On November 27, 2002 at 04:58:36, Russell Reagan wrote:

>On November 27, 2002 at 03:52:37, Ricardo Gibert wrote:
>
>>Consider backgammon. Despite the element of chance, alpha beta is still
>>applicable. Also, because if the element of chance, the game has a very high
>>branching factor. You must account for all possible rolls in addition to all the
>>possible legal moves with the checkers.
>>
>>The best backgammon programs play better than the best humans despite the high
>>branching factor. Humans do not really try to calculate all the possibilities,
>>so a program that searches just 3 ply ahead can outplay strong humans.
>>
>>The other oddity about backgammon is that the use of neural nets has actually
>>been effective for evaluation. This contrasts with the results in chess.
>>
>>If you are interested in reading more about this you can check out the following
>>site: http://www.bgsnowie.com/snowie/snowie.dhtml
>
>
>So is it fair to say that backgammon, despite having a high branching factor, is
>still playable by computers because it is a relatively simple game? For example,
>in backgammon, you say 3 ply is sufficient. Go programs can get 3 ply, but it's
>far from sufficient.

The number of plies is not the important factor.

In chess computers can get more plies in the endgame but it does not help them
to be relatively better against humans in the endgame.

I think that the main problem in go is that it is hard to define the evaluation
function.

I expect chess programs to get at least master level in chess even if you
increase the size of the board to 100*100.

Humans may have big problems in this game because it may take them time to
calculate if a move is legal.

in 8*8 the eye can see immediately that the rook cannot go from c1 to d8
in 100*100 board it is not going to be trivial to see that the rook cannot go
from y27 to z78

Uri



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