Author: Erik Robertsson
Date: 15:19:34 11/30/01
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On November 30, 2001 at 11:13:45, Robert Hyatt wrote: >On November 30, 2001 at 07:25:42, Erik Robertsson wrote: > >>I´ve been trying to correct some bugs wich occur when storing mate values in the >>hashtable. >> >>If the position is evaluated as a mate value at the end of an iteration in the >>iterative deepening, I stop searching and execute the best move. In some >>positions however, I find that due to finding positions in the hashtable it can >>result in the engine alternating between two different mate variations ending in >>a quite embarrassing draw by repetiton. >> >>I've tried to solve this by not automatically stop the iterative deepening >>unless I've found a shorter mate than found in the previous move. Is there a >>better way of solving this? I remember reading something about this some year >>ago, but cannot find it. >> >>I use the draft = *infinity* for mates wich are not bounds which should result >>in that most positions with mate should be in the ht in the next search. Maybe >>it has something to do with the bounds, but I´ve tried Crafty's MATE-300 bound >>and it sometimes result in getting the evaluation of the position as MATE-300. >> >>This has kept me awake a few nights, please help or I will go insane. > > >Are you correcting the mate scores before you store them in the hash >table? If you do this, there should never be a problem, with one exception. >It is easy for a program to find a non-optimal mate score and store it in the >hash table. And that can cause some confusion. But if you search with the >rule that says "I will not stop until either time runs out or I find a mate >in N-1 (where N was the mate score from the last real move played in the >game)." > >If you do both of those, you should not have any problems. But you _must_ >correct the mate score to be "mate in N from this ply" rather than "mate in >N from the root position".
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