Author: vitor
Date: 02:01:02 05/29/99
Go up one level in this thread
On May 29, 1999 at 00:03:09, Robert Hyatt wrote: >On May 28, 1999 at 18:07:17, vitor wrote: > >>as far as i can tell, zobrist hashing seems to be an imperfect(but fast) hashing >>scheme, meaning it is possible that your program will mistake position X as >>position Y. >> >>so my question is: >>is zobrist hashing the current standard in computer chess? is it just an >>accepted risk or are there any perfect hashing schemes that are used? > > >The term "perfect hashing scheme" is an oxymoron. There is no such animal, >_by definition_. Because you are reducing an N-bit quantity (if I recall, >from a mathematical discussion a few years ago, a chess board can be >represented in something just over 160 bits [I have not followed the discussion >here as this isn't a burning issue with me]) to an M-bit quantity, where >N >> M. IE I hash using 64 bits everywhere... which means there is _no_ way >to represent a chess board accurately in only 64 bits... since the original is >> 64 bits... im probably using the wrong terminology. what i meant by perfect hashing is that every position gets a unique id key. without a unique key as in zobrist, a program might mistake a collision for a match.
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.