Author: Robert Hyatt
Date: 05:45:45 10/08/98
Go up one level in this thread
On October 08, 1998 at 08:34:37, blass uri wrote: > >On October 08, 1998 at 08:28:10, Robert Hyatt wrote: > >>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. > >I did not see it announce a mate when there is no mate there but I saw it >announce mate in N when there is mate only in more than N >I remember that I tried a simple position of king and rook against king >(white king h1 rook g2 black king f3) and it announced mate in 10 when >I think that there is only a mate in 18 > >Uri it's actually a mate in 16... :) > >> >>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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