Author: Robert Hyatt
Date: 10:26:16 11/24/97
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On November 24, 1997 at 12:46:11, Ernst A. Heinz wrote: >On November 24, 1997 at 11:55:51, Chris Whittington wrote: >> >>Negative evals mean they just choose Na5 by chance as the least bad >>possibility. They don't have the knowledge, but they got lucky in this >>position. > >Not true, Chris. > >DarkThought understands that everything except Na5 *looses* and it also >understands that the resulting position is a draw as soon as the white >king gets into the corner. *But* Black need not let him get there -- by >aimlessly moving around with his king, bishop, and eventually his pawns. >Consequently, the position will be drawn *very far* in the future due to >the 50-moves rule. > >>Draw evals with a long and valid main line mean they really understand. > >Well, this main line should be well over 100 plies because Black still >has >some pawn moves ... > >Ah yes, I totally agree with you that it looks very complicated and >maybe >even foolish to try to assess the resulting position as drawn "at a >glance". > >=Ernst= In light of my testing, I'd simply call this a "broken" test position and throw it out. Anything but the knight sac loses outright, and most programs that can reach reasonable depth see this. I'd bet Fritz finds it quite quickly as well. But the solution is wrong, because the goal of the test was to test knowledge to see if a program could recognize that this is a draw. To do so requires an evaluation of 0.00, not -3. something, because there are plenty of -3 positions that are still dead lost. The point here, then, is only to search deeply enough to see that this move is the only way to avoid scores of -4 and worse. I ran it on Cray Blitz and it found this in 8 seconds, and liked the knight sac from then on. But the score never went above -3.8 or so, although I only let it search to depth=21. It averaged about 9.7 million nodes per second for comparison, but never had a clue that this was drawn, just that it was playing the only move that didn't lose within its horizon. (I don't have the output in front of me, but believe it found the knight sac at depth=16 or perhaps 17. I can rerun it if this is important... I don't count such "solutions" since I know that for every such lucky correct find, there are hundreds where such a knight sac only makes things easier for the opponent...
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