Author: Rick Bischoff
Date: 11:20:54 07/30/03
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On July 30, 2003 at 13:09:32, Robert Hyatt wrote: >On July 29, 2003 at 03:44:42, Rick Bischoff wrote: > >>Hi all, >> >>I am getting the following statistic from my program: >> >><pre> >> 0/18 0 1426407 Ke6 h3 Kd5 Rg2 Kc5 h4 Kb5 h5 Ka5 h6 Ka6 >>move found: 85570 not found: 118 >></pre> >> >>Which means of the 88570 times the hashtable didn't have a good value, it still >>had a good move to try first; the other 118 times it didnt have a good value, >>it had an illegal move... Is this the kind of percentage you all see in your >>engines? > > >I don't like the "illegal move" issue. How can you possibly store an illegal >move in the hash table? > >You have a good move to store if you back up a score that is > alpha, which >might mean you are backing up a PV, or a fail-high. You don't have a good >move if you are backing up alpha, because _every_ move failed low and there is >no way to know which is best... > >But storing an illegal move is something that should not happen. If you back >up alpha, set the hash move to zero. Dr. Hyatt, Indeed that is what I do-- I was getting illegal moves from the way I encode moves.. However, it is still possible that an illegal move is in the hash if two positions share the same key and map to the same key.
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