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Subject: Re: 0x88 vs 144 (or 12x12)

Author: Dann Corbit

Date: 23:09:55 10/25/02

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On October 26, 2002 at 00:42:16, Russell Reagan wrote:

>In reading one of those old posts, Christophe Theron was talking about how he
>did his pawn evaluation in a pawn hash table. I'm curious if this is a good
>idea. There are obviously far fewer pawn formations than there are chess
>positions. It seems unsound, but then again so did a transposition table using a
>hash table implementation at first thought.

Pawn hash is an old idea and almost all of the good programs do it.

Score the pawn formation separately...

Usually, the king is included in the pawn hash as well, since their relationship
is very important.

You don't score the pawn attacks at this stage... Just look for things like:
1.  Passed pawns
2.  Doubled pawns (and tripled pawns)
3.  Pawn islands
4.  Opening in pawns shelter for the king
5.  Isolated pawns

None of that stuff changes for all the things the other pieces on the board do,
so you can hash it.

Small subset of programs using Pawn hash:
Amateur
Amy
Arasan
AX
Baron
Beaches
Bestia
Betsy
BremboCE
Butcher
Crafty
Crux
Delfi
Esc
Freyr
Gargamella
Lambchop
Leila
Madeleine
Monsoon
ExChess
Gerbil
GnuChess
Gullydeckel
KNIGHTD3
Pepito
Resp
Sjeng
SSEChess
TAO
The Crazy Bishop

Lots more besides these, I imagine -- I got tired of looking



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