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Subject: Re: Zugzwang

Author: Mikael Bäckman

Date: 03:26:17 09/11/04

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On September 10, 2004 at 10:18:30, Mihaly Szalai wrote:

>From the game Jung - Szabados (1952)
>
>[D]8/6B1/p5p1/Pp4kp/1P5r/5P1Q/4q1PK/8 w - - 0 32
>
>32. Qxh4! Kxh4 33. Bf6+ g5 34. Bc3!!
>
>Hiarcs 9 have problems with it even after 20 minutes.
>
>Show it to your engine.
>
>Thanks
>Mihaly


I recently started playing around with verified nullmove pruning in Chepla. In
this position the difference between what I normally use (adaptive R=2/3) and
VNMP is huge: 6 plies!


With R=2/3:

  -0.18    2193k   3.0 Bh6+ Kxh6 Qxh4 Qe5+ Kg1 Qe3+ Kf1 Kg7 Qe4 Qxe4 fxe4 Kf6
                       Ke2 Ke5 11/25
  -0.17    3065k   4.3 Bh6+ Kxh6 Qxh4 Qe5+ Kg1 Kg7 Kf2 Kf7 Qe4 Kf6 Qxe5+ Kxe5
                       Ke3 g5 g3 12/26
  -0.12    6047k   8.5 Bh6+ Kxh6 Qxh4 Qe5+ Kg1 Qe3+ Kf1 Qc1+ Kf2 Qd2+ Kf1 Qd3+
                       Kg1 Kg7 Qe7+ Kh6 Kf2 g5 Qe4 Kg7 13/29
   0.16    9534k  13.0 Qh3xh4+! Kxh4 Bf6+ g5 Bc3 Qf2 Be5 Qd4 Bxd4 g4 13/22
   1.16    9558k  13.0 Qh3xh4+! Kxh4 Bf6+ g5 Bc3 Qf2 Be5 Qd4 Bxd4 g4 13/21
   4.29   10216k  13.8 Qh3xh4+ Kxh4 Bf6+ g5 Bc3 Qf2 Be5 Qg1+ Kxg1 g4 f4 g3 f5
                       Kg5 f6 Kg6 Kf1 Kf7 Ke2 Ke6 14/26
   4.29   12905k  16.7 Qh3xh4+ Kxh4 Bf6+ g5 Bc3 Qf2 Be5 Qg1+ Kxg1 g4 f4 g3 f5
                       Kg5 f6 Kg6 Kf1 Kf7 Ke2 Ke6 15/28


With VNMP:

  -0.19       4k   0.0 Bh6+ Kxh6 Qxh4 Qe5+ Kg1 Kg7 Kf2 5/11
  -0.27      15k   0.0 Bh6+ Kxh6 Qxh4 Qe5+ Kg1 Kg7 Kf2 Kf7 6/15
  -0.27      53k   0.1 Bh6+ Kxh6 Qxh4 Qe5+ Kg1 Qe3+ Kh2 Kg7 Qe4 Qc3 7/17
   0.06     115k   0.2 Qh3xh4+! Kxh4 Bf6+ g5 Bc3 Qf2 Be5 Qd4 Bxd4 g4 fxg4 7/18
   1.06     117k   0.2 Qh3xh4+! Kxh4 Bf6+ g5 Bc3 Qe5+ Bxe5 g4 fxg4 hxg4 g3+ Kg5
                       Kg1 7/17
   3.86     158k   0.3 Qh3xh4+ Kxh4 Bf6+ g5 Bc3 Qf2 Be5 Qg1+ Kxg1 g4 Kf2 Kg5
                       f4+ Kf5 Ke3 8/22
   3.86     359k   0.6 Qh3xh4+ Kxh4 Bf6+ g5 Bc3 Qf2 Be5 Qg1+ Kxg1 g4 Kf2 Kg5
                       f4+ Kf5 Ke3 9/27
   4.10     996k   1.6 Qh3xh4+ Kxh4 Bf6+ g5 Bc3 Qf2 Be5 Qg1+ Kxg1 g4 f4 g3 f5
                       Kg5 f6 10/26



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