Author: Robert Hyatt
Date: 06:21:58 06/23/98
Go up one level in this thread
On June 23, 1998 at 06:21:36, Ernst A. Heinz wrote: >On June 23, 1998 at 03:58:26, Ulrich Tuerke wrote: > >>On June 22, 1998 at 16:11:47, John Stanback wrote: >> >>>This is a nice position for testing/debugging transposition >>>tables and draw by 50 move rule. I modified Zarkov to allow >>>it to search beyond 100 plies, but it didn't find the draw. >>>Then I added 1 line of code to store positions which were >>>scored by the 50 move rule or draw by repetition in the >>>transposition table before returning from search(). Now it >> >>I'm afraid this can imply some problems for the search. Assume >>that you have flagged a position as a "draw" in your transposition >>table because the 50 move rule had applied. If this position is later >>reached at a lower depth via a transposition, then the hash table >>would return a "draw". But may be, it really isn't because at lower >>depth the search might be still below the 50 move threshold ? >>This could result in real foolish moves returned from the t-table. >>IMHO, similar remarks hold for the draw by repetition case. >> >>I think that I had once detected problems through storing these >>kinds of positions in the hash table. Now, I don't store them. >> >>Did I get somehing wrong ? > >I do not think you got something wrong -- I completely agree with you. > >=Ernst= It's a problem, but it is just as bad to ignore this. If you have to choose between errors with, and errors without, why not take the performance gain? I store everything and haven't seen any ugly effects doing so that I don't see if I disable such. Dave Slate always said "don't store draws". Ken Thompson said "store everything". I go along with the latter...
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