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Subject: Re: 10 ply from starting position

Author: Robert Hyatt

Date: 15:07:35 07/13/02

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On July 13, 2002 at 12:32:39, Richard Bean wrote:

>On July 13, 2002 at 10:30:28, Robert Hyatt wrote:
>
>>>6      119060324      9417681
>>>The reason I differ from Steven Edwards for the number
>>>of unique nodes at ply 6 is that after the moves
>>>1. f4 e6/e5 2. Kf2 Qf6 3. f5 g5, no ep capture is possible,
>>>so I get 2 less unique nodes than him.
>>>
>>
>>This is _supposed_ to be _legal_ moves only.  I don't therefore see
>>why Steven would be counting an EP move that can't be made...
>
>I'm counting unique nodes at ply 6 - you can look
>at http://www.it.ro/ccc_search/ccc.php?art_id=147499
>and check that Andreas Stabel got 2 less nodes when he counted positions as
>unique only if ep captures were legal.
>
>What I'm really saying is: consider the positions after the moves
>
>1. f4 e6 2. Kf2 Qf6 3. f5 g5 - a
>1. f4 g5 2. Kf2 e6 3. f5 Qf6 - b
>1. f4 e5 2. Kf2 Qf6 3. f5 g5 - c
>1. f4 g5 2. Kf2 e5 3. f5 Qf6 - d
>
>I think Steven Edwards has counted this as four unique positions whereas
>I only count it as two, because 4. fxg6 is illegal in a and c and
>impossible in b and d.


OK.. first my "perft" implementation doesn't count "positions".  It simply
counts each time a valid move is "made".  So I don't have the problem you
are describing, because I don't try to compare the positions to see if they
are equal.  IE transpositions don't affect my counts at all...




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