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Subject: Re: Ply Results

Author: Andreas Herrmann

Date: 14:07:23 05/28/03

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On May 28, 2003 at 16:25:54, William H Rogers wrote:

>I'll give you only one or two examples.
>Initially there are 20 possible moves for white and assuming that the Kings pawn
>makes the first move then there are 20 possible moves for black.
>That equals 20*20=400 moves for a two ply search.
>Continuing on with the same opening moves now there are 29 possible moves for
>white once again, that equals 400 * 29 = 11,600 moves for three plys.
>Then numbers grow from that point up. Set up a board and try it yourself.
>His statement is that at two plys there are a total of 420 moves. He is getting
>confused by adding the original 20 to the new 400 possible moves that already
>include the original 20, and he carries this flawed logic throughoput his
>equations. It is a simple matter of doing the math...
>I hope this helps to see the errors of his ways. In all other respects his page
>looks real good, and I am sure that some people will benifit from it.
>Bill

There is nothing wrong. Please read his description. If you count only the
frontier nodes, than you got the perft value. If you add all moves from ply 1 to
n then you got the total moves count.
And his perft values are verified by a lot of engines, which supports the perft
command. You can verify this for excample with Crafty, Yace, Gaviota, Pepito and
a lot of other engines.

Andreas






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