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Subject: Re: Which programs can access 6-piece tablebases...

Author: Uri Blass

Date: 05:05:15 02/21/05

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On February 21, 2005 at 06:30:57, Tony Werten wrote:

>On February 21, 2005 at 04:12:55, Uri Blass wrote:
>
>>On February 21, 2005 at 03:54:03, Dieter Buerssner wrote:
>>
>>>On February 20, 2005 at 18:51:41, Dieter Buerssner wrote:
>>>
>>>>On February 20, 2005 at 18:40:34, Guido wrote:
>>>>
>>>>>You are right but if I remember well there is a mate in 127 and a loss in 127 in
>>>>>kppkp and another score to add is illegal position.
>>>>>So for kppkp it is necessary at least 9 bits. You could use the illegal position
>>>>>score meaning loss in 127, as illegal positions are not possible in the game.
>>>>
>>>>Hi Guido! IIRC, 8 bits was just enough for kppkp and all 256 numbers were used.
>>>>kppkp wtm has mate in 127, btm has lost in 127, together with draw and broken
>>>>positions, this exactly fits the 256 states possible in one byte.
>>>
>>>Oops, you were right, it seems. I forgot about loss in zero. Sorry for my
>>>useless post. BTW. the max positions here give fast Q-endgame, which is draw due
>>>to 50 moves rule.
>>>
>>>Dieter
>>
>>I do not understand.
>>
>>Do you say that computers with the old tablebases evaluate the max position as >a draw instead of mate and that they are right because of the 50 move rule?
>>
>
>Nope, they evaluate the max position as a win instead of a draw and they are
>wrong because of the 50 move rule :)
>
>Tony
>
>>Uri

I do not understand.

How they can evaluate it as win when the table is broken because of 257 values.
Do they say mate in 0 instead of mate in 127?

Note that from movei point of view mate in 0 can be considered by tablebase as
broken position with no change in playing strength.

I think that using tablebases to find if position is mate is very expensive way
that is not needed.

Uri



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