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Subject: Re: hanging pieces in rebel

Author: Robert Hyatt

Date: 09:33:53 01/17/04

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On January 17, 2004 at 02:38:24, rasjid chan wrote:

>On January 16, 2004 at 16:31:17, Robert Hyatt wrote:
>>On January 16, 2004 at 12:07:00, Tord Romstad wrote:
>>>On January 16, 2004 at 10:02:39, Robert Hyatt wrote:
>>>>I would worry about overflow there.
>>>>IE e4 could be attacked by pawns on d3 and f3, a bishop at d5 with a queen
>>>>behind it (4 so far), plus two rooks and two knights.  That's 8.  It just
>>>>overflowed to zero.  Not to mention the promotion problems where there is a
>>>>third knight or bishop or second queen...
>>>It is not so dangerous if you are just a bit careful about where and how
>>>you use the information.  I use it mostly in the evaluation function, in
>>>order to compute stuff like mobility, space and king safety.  That one
>>>or two squares on the board are evaluated incorrectly once every hundred
>>>nodes or so usually does not have any catastrophic consequences.
>>>You are of course right that an SEE based on this simple kind of attack
>>>tables is not reliable enough to be used to replace a qsearch.  For this
>>>purpose, I use a much slower and more accurate SEE.
>>I was more worried about the actual overflow.  IE if this is a char, 8 attackers
>>appears to be zero.  If it is packed into a word, then 8 attackers wraps into
>>the next char to the left and corrupts that...
>I think there is no overflow. His BIT0 is the LSB. 8 attacker overflows to
>pawn attacking so almost it will be true. having 2 queen almost mean game
>decided. Extra Knights or Bishop has other simple solution.

The game might not be so decided if your extra queen screws up evaluation and
capture analysis.  :)

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