Author: Uri Blass
Date: 22:37:02 02/10/02
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On February 10, 2002 at 21:36:22, Brian Katz wrote: >This is wierd. >Whether Black promotes to a queen or under promotes to any other piece, the >position will be identical after the white rook recaptures. After the rook >recaptures on a1, it gives mate in 19 after Black plays 64...Kg7. However, if >you actually play 64...Kg7, Fritz then announces mate in 16. >Then it changes that and gives mate in 35 after 64...h5. >I find that simply 65.Ra6+ Kg7 66.Ke5 Kf7 67.Rd6 Ke7 68.b6 h4 or ANY is mate in >4 moves. 69.b7 Kf7 70.b8=Q Ke7 71.Qc7+ Kf8 72.Rd8 mate. >This was in the infinite analysis mode. >Isn't this just wasted processing time? Finding mates in over 260 moves, in the >event that the winning side does not play the best moves just seems to get in >the way of more valuable analysis. Granted,in the given position there is no >risk of losing due to searching to deeply into pointless lines,but, does this >happen during the course of the whole game. >I guess increasing the selective search may correct that somewhat. >Brian I doubt if fritz7 searchs so deep. I tend to believe that it does not and the bug is simply in counting the number of plies to mate. Maybe it is using hash tables and the hash tables tell it that some position is mate in at most 7 it later gets into this position from another position and find that the second position is mate in 8 and later in another line in the search it gets to the mate in 8 position to see mate in 13 in another position and continue in this way. I do not believe that all 529 plies are in the same line that it searches from the root. Uri
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