Author: Robert Hyatt
Date: 19:54:44 04/25/00
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On April 25, 2000 at 14:25:08, José Antônio Fabiano Mendes wrote: >On April 24, 2000 at 23:15:23, Robert Hyatt wrote: > >>On April 24, 2000 at 22:34:28, Dann Corbit wrote: >> >>>On April 23, 2000 at 18:13:42, Robert Hyatt wrote: >>> >>>>On April 23, 2000 at 17:15:52, Michael Fuhrmann wrote: >>>> >>>>>Why would a program ever underpromote to a rook? Saw Crafty do this recently. >>>>>(In this particular case, it had no impact on the outcome of the game.) >>>> >>>> >>>>1. it is necessary at times. IE if you promote to queen, you stalemate your >>>>opponent. if you promote to rook, you can still win without stalemating him. >>>> >>>>2. In the case of chess engines, it is pretty common to see this. The most >>>>common reason is that the =R is not a check, when the =Q is a check, or the >>>>rook allows fewer checks later in the tree. So by promoting to a rook, it >>>>avoids some tactic that it really can't avoid... IE this is a horizon effect >>>>situation.. >>> >>>Are there any cases where you would promote to bishop or rook to achieve >>>stalemate for yourself? (e.g. you are far behind in material (say down two >>>queens or more), and the only legal move is the pawn promotion or something of >>>that nature) >> >> >>Sounds hard.. but I'll bet there is a problem composer out there that might >>construct such a position... > >http://www.xs4all.nl/~timkr/chess2/minor.htm [comprehensive!] I just _knew_ there was someone weird enough to do this. :) Harry Nelson and Lazlo Lindner (I am not sure about the spelling) were good friends and were always posing ridiculous positions to Cray Blitz. One was the famous 218 move position that blew the move vector out (the assembly language had an assumption of three 64 word segments to the move list only, which was barely not enough for that oddball case. They also used to try the 'straightjacket' positions that were composed... ie "what is the longest sequence of forced moves for both sides that ends in mate for one." So the g8=B+ draw is not surprising. :)
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