Computer Chess Club Archives


Search

Terms

Messages

Subject: Re: regular hash key & pawn hash key together--good idea?

Author: David Blackman

Date: 01:51:27 09/16/99

Go up one level in this thread


On September 16, 1999 at 04:00:43, Tom Kerrigan wrote:

>If you have a program with 64 bit hash keys, is it a good idea to devote n bits
>to pawns and the rest to pieces and side-to-move?

If you need a pawn hash for fast pawn eval, and a full hash for transpositions
etc, then calculating them both into one 64 bit quantity probably makes things a
bit faster. However it increases the probability of various kinds of false
matches.

I think it will probably work out ok, but be careful. You might want calculate
an additional 64 bits just for testing purposes so you can count how many false
matches you get from the first 64. This would be turned off when you have to run
fast of course.

>I was thinking a good balance may be 24 bits for pawns, but I have no data to
>back this up. Does anybody else?
>
>-Tom

Pawns make up about half the pieces on the board, and a little less than half
the information content (because there are 2 sorts of pawns and 10 sorts of
other pieces), so i guess about 24 to 30 bits for the pawns is the right
proportion.



This page took 0 seconds to execute

Last modified: Thu, 15 Apr 21 08:11:13 -0700

Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.