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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