Author: Pham Minh Tri
Date: 16:35:46 05/24/01
Go up one level in this thread
On May 24, 2001 at 09:01:52, José Carlos wrote: >On May 24, 2001 at 08:57:43, Robert Hyatt wrote: > >>On May 24, 2001 at 08:55:15, Pham Minh Tri wrote: >> >>>On May 24, 2001 at 08:14:37, Gian-Carlo Pascutto wrote: >>> >>>>On May 24, 2001 at 07:50:32, Pham Minh Tri wrote: >>>> >>>>>Hi, >>>>>I heard that the hash technique could apply to opening book. Could someone >>>>>explain to me how to use and what is the benefit? >>>>>Thank very much in advance, >>>>>Pham >>>> >>>>Quite simple. Instead of storing positions or sequences you store >>>>the hashes of the positions. >>>> >>>>The benefit is space. If you were storing sequences you will also >>>>spot transpotions now. >>>> >>> >>>Could you explain more detail? I still do not understand. The 64 bit hash key is >>>always bigger than 16 bit of a move representation, and the random numbers may >>>make the hash key after moving totally different from the old one, so how to >>>save space? >>> >>>And another question: does this technique need more computing (to match and >>>extract) than the normal technique (use other kind of database)? >>> >>>Thanks, >>> >>>>-- >>>>GCP >> >>To build the book, make the first move in the book line, say e4. Store the >>hash signature _after_ that move is made. Then for other first moves (say d4) >>do the same. >> >>When you want to use the book, generate all legal moves, make each one, one >>at a time, and after making one, check to see if the current hash signature >>matches a signature in the book file. If so, this move is a "book move". > > And (to Pham) do not forget to use _always_ the same random numbers to >generate the hash keys :) > The biggest benefit of this technique is that it makes trivial to handle >transpositions. > > José C. Thanks for suggestions. But I guess that: 1) Hash technique makes opening books 4 times bigger than the old one in which I save only sequences of moves (because 64 bit hash key for a move is 4 times as big as 16 (or 14) bit of a move). 2) It is slower than the old one because I have to generate all legal moves, do them, then match, instead of matching only. Do I miss something?
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.