Author: Bob Durrett
Date: 06:08:17 07/23/03
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On July 23, 2003 at 02:32:48, Odd Gunnar Malin wrote: >On July 22, 2003 at 18:24:38, Bob Durrett wrote: > >> >>If all chess engines utilize their hash tables in much the same way, might there >>be some benefit in standardizing the tables and standardizing the way data is >>stored in them? Could a way be found to switch engines but keep the same hash >>table and it's contents? >> > >The important values in the hashtable are evaluation-score together with a depth >(ply) parametre for a position. If this should be reused in another engine the >evaluation score must be the same for the same position. Are you sure about that? I always felt that the biggest difference between engines was in the pruning. i.e. one engine may consider lines/positions pruned away by another. For example, one engine may consider certain positions to be important and store the information about those positions in it's hash table. Then if that hash table were "frozen" and subsequently the engine switched, after which the new engine "unfroze" the hash table and started using it and it's data, then the new engine might not consider some of the positions important because the new engine prunes out the lines which created those hash table entries. The whole motivation for this idea was to somehow prompt the new engine to consider results it would not otherwise have found. It is not clear, however, whether the new engine would even "see" this information. >Eg. the only difference >between engines are speed. >This is of course not wanted and even when you adjust a parametre in the same >engine you have to clear the hash table before a new search. > >Within the same engine you could freeze the hashtable if you want to use the PC >for another job or run another engine. I only know of Winboard engines that can >do this (it is in the protocol). This frozen hashtable could be saved to a file >for later use, but maybe only a feature for a corr. player. I don't know any >engine with this ability. > >Odd Gunnar The "frozen hashtable" idea is interesting! : ) Bob D.
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