Author: Robert Hyatt
Date: 05:28:10 10/08/98
Go up one level in this thread
On October 08, 1998 at 04:35:57, blass uri wrote: > >On October 08, 1998 at 04:28:13, Kai Lübke wrote: > >>On October 08, 1998 at 02:03:56, blass uri wrote: >> >>> >>>On October 07, 1998 at 23:33:53, James T. Walker wrote: >>> >>>>I gave Fritz 5.16 a position /p4K/P////k// W. I think that I have that figured >>>>out right. Anyway, Fritz announces #14 after about 16 sec. But when you go >>>>through the moves it announces #13 twice, #10 twice,#8 followed by #9 etc. It >>>>jumps from #6 to #4 no matter what move I make in that position. After that it >>>>counts on down to mate properly. It ends up with about a mate in 17. What >>>>causes this phenom ? Crafty with the same position announces #17 on the first >>>>move then while pondering it finds mate in 15. After that it counts down by one >>>>to mate. That seems fairly normal. >>>>Jim >>> >>>Fritz never knew to count >>>It was designed to play chess and not to count the number of moves to mate >>> >>>I think that this is because of hash tables >>>Maybe fritz found that some position leads to mate and remember it in the hash >>>tables as mate without the number of moves >>> >>>After it go to the same position again in the search it evaluates it as >>>checkmate without number of moves and this is the reason that it cannot count >> >>The "mate in 8, then on the next move mate in 9" stuff is something you often >>see in Fritz engines (Hiarcs and Junior have the same problems sometimes). >>Crafty has a special code that assures that a "mate in N" is never followed by >>a "mate in N+k" where k>=0. >>I'm just waiting for someone to find a position where Fritz will not be able to >>mate because of this... :-) >> >>--- >>Shep > >The main problem with fritz is that often the mate in N is only an illusion of >fritz. > >It is a bad idea to use a special code for fritz telling it to look after mate >in N only for mate in N-1 or less before solving this problem because the result >may be: no mate found. > >Uri I don't believe that fritz is ever *wrong* when it announces a mate. It might say mate in 10 when there is a mate in 6 that can be played. But I have *never* seen a program announce mate in N when there is no mate there, unless it is a new program with bugs. But *if* you find a mate in N, after your opponent plays a move, it will not hurt a thing to search until you find a mate in N-1... even if you can't find it time will stop you eventually, and in 99.99% of the times the N-1 mate is there and can be found within the time limit...
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