Author: Dan Homan
Date: 12:23:02 11/05/99
Go up one level in this thread
On November 05, 1999 at 12:39:20, David Eppstein wrote: >This and the many other null-move-killer positions regularly posted here seem to >show that crafty's simplistic check (avoid null move when side to move has only >one non-queen piece) could stand some improvement. What better algorithms are >other programs using to tell when a position might be zugzwang? I vaguely >remember a commercial programmer (Christophe or Ed?) making a cryptic comment >about double-null-move solving this problem, but I didn't understand what that >might mean. This is an interesting idea, so I just now put a *very* simple verification search into my null move algorithm. Basically, if a null move cut is about to happen, I just search the position normally - no null move - but still to reduced depth to check if there are an zug problems. Seems to work well on this position.... Below are the results from my program with null move - ON - but with the simple verification search I described above. Compare this to the results with null move - OFF (a couple of messages above). I find b5+ a few plys later (due to the reduced depth of the verification search), but I can go *much* faster. I'll keep tinkering with this verification search... - Dan BTW: With null move - ON, but no verification search, I don't find this move up to ply 13 (completed at 71 seconds). White-To-Move[1]: setboard 4q/p5p/k5P/8/1PN4K/8/1N2B/8 w - - White-To-Move[1]: analyze Analysis mode: Enter commands/moves as ready. 1. -0.29 0 5 1. b5+ 1. 0.69 0 20 1. Ne5+ 1. 0.74 0 38 1. Bh5 1. 0.83 0 39 1. Bd3 1. 0.83 0 47 1. Bd3 2. -0.09 0 97 1. Bd3 Qe7+ 2. 0.68 0 387 1. Ne3+ Kb7 2. 0.76 0 661 1. Ne5+ Kb6 2. 0.76 0 664 1. Ne5+ Kb6 3. 0.77 0 1126 1. Ne5+ Kb7 2. Bf3+ 3. 0.77 0 1746 1. Ne5+ Kb7 2. Bf3+ 4. 0.72 0 2877 1. Ne5+ Kb7 2. Nbd3 Qd8+ 4. 0.72 0 4944 1. Ne5+ Kb7 2. Nbd3 Qd8+ 5. 0.67 0 13867 1. Ne5+ Kb6 2. Nbd3 Qe7+ 3. Kg4 5. 0.67 0 19104 1. Ne5+ Kb6 2. Nbd3 Qe7+ 3. Kg4 6. 0.70 0 29093 1. Ne5+ Kb6 2. Nbd3 Qb5 3. Kg4 a5 6. 0.70 0 43143 1. Ne5+ Kb6 2. Nbd3 Qb5 3. Kg4 a5 7. 0.72 0 65244 1. Ne5+ Kb6 2. Nbd3 Qb5 3. Kg4 a5 4. ba5+ 7. 0.72 0 91558 1. Ne5+ Kb6 2. Nbd3 Qb5 3. Kg4 a5 4. ba5+ 8. 0.72 1 130795 1. Ne5+ Kb6 2. Nbd3 Qb5 3. Kg4 a5 4. ba5+ Kc7 8. 0.72 1 199550 1. Ne5+ Kb6 2. Nbd3 Qb5 3. Kg4 a5 4. ba5+ Kc7 9. 0.73 2 300281 1. Ne5+ Kb6 2. Nbd3 Qb5 3. Kg4 a5 4. ba5+ Kc7 5. Bf3 9. 2.33 2 321411 1. b5+ Qxb5 2. Nd3 Qxc4+ 3. Nf4 Qxe2 4. Nxe2 Kb6 5. Nd4 9. 2.33 2 442444 1. b5+ Qxb5 2. Nd3 Qxc4+ 3. Nf4 Qxe2 4. Nxe2 Kb6 5. Nd4 10. 5.47 3 654531 1. b5+ Qxb5 2. Nd3 Qb8 3. Nc5+ Kb5 4. Ne5+ Kc5 5. Nd7+ Kd6 10. 5.47 5 970055 1. b5+ Qxb5 2. Nd3 Qb8 3. Nc5+ Kb5 4. Ne5+ Kc5 5. Nd7+ Kd6 11. 5.48 6 1087464 1. b5+ Qxb5 2. Nd3 Qb8 3. Nc5+ Kb5 4. Ne5+ Kc5 5. Nd7+ Kd6 6. Nxb8 11. 5.48 9 1730070 1. b5+ Qxb5 2. Nd3 Qb8 3. Nc5+ Kb5 4. Ne5+ Kc5 5. Nd7+ Kd6 6. Nxb8 12. 5.38 19 3297119 1. b5+ Qxb5 2. Nd3 Qb1 3. Nc5+ Kb5 4. Na3+ Kc5 5. Nxb1 a5 6. Nc3 Kb4 12. 5.38 28 5215214 1. b5+ Qxb5 2. Nd3 Qb1 3. Nc5+ Kb5 4. Na3+ Kc5 5. Nxb1 a5 6. Nc3 Kb4 13. 4.24 52 8607734 1. b5+ Qxb5 2. Nd3 Qxc4+ 3. Nf4 Qxe2 4. Nxe2 Kb6 5. Kg5 a5 6. Nd4 a4 7. Nf5 13. 4.24 90 13186425 1. b5+ Qxb5 2. Nd3 Qxc4+ 3. Nf4 Qxe2 4. Nxe2 Kb6 5. Kg5 a5 6. Nd4 a4 7. Nf5
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