Author: Andrew Williams
Date: 11:47:42 06/13/04
Go up one level in this thread
On June 13, 2004 at 14:24:57, GeoffW wrote:
>Hi
>
>I was thinking how I would add pawn hashing to my program. Having read a little
>of the Crafty source I have a rough grasp of the idea, however there are a
>couple of things I am hazy on.
>
>Q1)
>I understand the pawn hash score stored must not contain any piece related
>scoring as that must be factored in later. In my program even the simple choice
>of which pawn position look up table is determined by the phase of the game, i.e
>it will be piece dependent. How would I get over that obstacle ? Score the pawns
>for end game, opening and middle in the hash, and choose which one to use later
>?
>
What I do is to hash in the game stage as well, so I could end up with three
separate entries in the pawn hash table for the same constellation of pawns.
>Q2)
>Crafty uses an 8 bit bitmap to store file for passers, this is ok for a bitboard
>program as it is probably trivial to find the exact location later. However for
>a non bitboard program it is non trivial to find the exact locations. Do I have
>any alternative but to store the passer locations in the hash ? That would be 16
>bytes just for the passed pawns for both sides?
>
If store two 8-bit words for each of:
passers
candidate passers
weak pawns
When I grab the entry from the table, I find the relevant pawns by walking up
the relevant file. I've not looked at crafty's approach, but it sounds like it's
the same.
>Hope my questions made sense I typed them quickly as the England match is about
>to start, must dash ...................
>
Me too!!
Andrew
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