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Subject: Re: Tablebase statistics

Author: Mike Hood

Date: 11:18:30 04/07/02

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On April 07, 2002 at 07:27:48, Sergei Smith wrote:

>Which 5-man tablebases are used most ?
>Some tablebases hardly ever get used and just take vauable disk space.

It's not really a question of which tablebases are "used" most, it's a question
of which are "needed" most. ie, If an endgame is difficult for a computer to win
with its computational algorithms, there should be a tablebase to help it. For
instance, KBN-KN will very rarely come about in real games, whether they are
human-human, human-computer or computer-computer. However, if such a game does
crop up a program that doesn't use tablebases will screw up with 99% certainty.
On the other hand, the endgame KR-K (or KRP-K) is a common endgame, but a
computer program will have no trouble finding mate without using tablebases.

Another factor is that tablebases aren't just used when the endgame position is
on the board. The 5-piece table bases are often used when there are 10 or more
pieces on the board, if the program's search tree sees a path that exchanges
pieces.

Now let me attempt a very general answer:

The tablebases Kxxx-K are less useful than the tablebases Kxx-Kx. There are only
a few extreme positions where Kxxx-K isn't a win, and chess programs should be
able to handle these endgames.

Everything with pawns is very useful (KxP-Kx and Kxx-KP)

The rest is more or less common sense. If it's an endgame you think is easy, the
chances are that computer programs will share your opinion. For instance, the
tablebases KQQ-Kx (even where x=Q) are less useful. The same is true for KQx-KN
and KQx-KB.

But having said this... if in doubt, keep all the tablebases. The complete
collection of 3/4/5-piece tablebases is 7 GB, which isn't much considering the
size of today's hard drives.




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