Author: Bruce Moreland
Date: 09:39:03 06/23/98
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On June 23, 1998 at 03:58:26, Ulrich Tuerke wrote: >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 ? No, but you didn't get everything right, either. Draw scores don't just affect one node, they can propagate up the tree, and they can cause other nodes to have a different value, without that value necessarily being the draw score. So as long as you have a transposition table that doesn't take into account the path used to get to a node, there will always be problems. And taking into account the path used to get to a node defeats the purpose of a transposition table. So if you don't store 50-move and rep draws at the point you encounter them, maybe this will make things work better, but you can't say, "whew, it is perfect now", either. bruce
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