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Subject: Re: Crafty-IsiChess,CCT4,r11 ==> A move to avoid?

Author: Uri Blass

Date: 15:01:34 01/29/02

Go up one level in this thread


On January 29, 2002 at 16:54:20, Dann Corbit wrote:

>On January 29, 2002 at 16:43:28, Roy Eassa wrote:
>
>>On January 29, 2002 at 16:36:23, Thomas Mayer wrote:
>>
>>>Hi Roy,
>>>
>>>>>Wow, Fritz 7b is blind to this one.  It does not see in advance that 37...Nxe5
>>>>>is good for Black (it thinks Black is down more than 3 pawns).  Must be
>>>>>null-move / zugzwang, right?
>>>>
>>>>
>>>>To be more specific, in the following position Black can play ...Re6 and be in
>>>>very good shape (certainly not behind).  However, Fritz 7b evaluates this
>>>>position as being better for White by about 5 pawns:
>>>>
>>>>[d] 8/8/1p1r1k2/p1pRN1p1/P3K1P1/1P6/8/8 b - - 0 2
>>>
>>>strange... Quark fully disagrees and thinks that black is little bit better...
>>
>>
>>Quark is right.  Fritz is wrong.
>>
>>I guess this is a very good example of a blindness caused by using null move.
>>
>>My question is, do all zugzwang positions confound null move, or only some?
>
>Since Thomas uses NULL MOVE in Quark, it makes you wonder what could be causing
>the blind spot for Fritz?  Using it past the time when it is appropriate
>perhaps?

I guess that Fritz and Quark do not use the same null move algorithm
I guess that Fritz prunes also in the main line when it see no threat and can
have a main line of only one move when it see no threat when part of the other
null movers do not do it.

Note that the more interesting position is the position 2 plies before Ne5

Here is some analysis on a slow p200 of another null mover
I guess that a lot of null movers will never find Nxd5 and only one ply after
Nxd5 they are going to find that one is better.

It seems that they do not assume that the opponent can reply with no moves to
the main line when Fritz does assume it so they will understand the position
after 1...Nxd5 when Fritz is not going to understand it.

New position
[D]8/8/1p1r1k2/p1pPN1p1/P3KnP1/1P6/8/3R4 b - - 0 1

Analysis by Crafty 18.07:

1...Ke7
    (0.32)   Depth: 1/5   00:00:01
1...Ke7 2.Kf5
    (0.32)   Depth: 2/5   00:00:01
1...Ke7 2.Kf5 Nxd5 3.Kxg5
    (0.42)   Depth: 3/7   00:00:01
1...Ke7 2.Nc4 Rf6 3.d6+ Kd7 4.Nxb6+
  +-  (1.93)   Depth: 4/9   00:00:01
1...b5 2.axb5 Kg7 3.Nc6
  +-  (1.86)   Depth: 4/9   00:00:01
1...Ne2
  +-  (1.46)   Depth: 4/9   00:00:01
1...Ne2 2.Rf1+ Kg7 3.Rf7+ Kh6 4.Rf8
    (1.02)   Depth: 4/9   00:00:01
1...Ne2 2.Rf1+ Kg7 3.Nc4 Ng3+ 4.Ke5 Rxd5+ 5.Kxd5 Nxf1 6.Nxb6
    (0.96)   Depth: 5/10   00:00:01
1...Rd8 2.Nc4 Rb8 3.d6 Re8+ 4.Kf3
    (0.79)   Depth: 5/10   00:00:01
1...Rd8 2.Nc4 Rb8 3.d6 Re8+ 4.Kf3
    (0.39)   Depth: 6/12   00:00:01  19kN
1...Rd8 2.Rh1 Rxd5 3.Rh6+ Kg7 4.Rxb6 Rd4+ 5.Kf5
    (0.36)   Depth: 6/12   00:00:01  23kN
1...Rd8 2.Rh1 Rxd5 3.Rh6+ Ke7 4.Rxb6 Rd4+ 5.Kf5 Nd5
    (0.36)   Depth: 7/14   00:00:01  36kN
1...Rd8 2.Nc4 Ne2 3.Rf1+ Kg7 4.Rf3 Nd4 5.Rh3 Re8+ 6.Ne5
    (0.80)   Depth: 8/18   00:00:03  141kN
1...Ne2 2.Rf1+ Ke7 3.Rf7+ Ke8 4.Rf3 Nd4 5.Rh3 Ke7 6.Re3
    (0.65)   Depth: 8/18   00:00:05  243kN
1...Ne2 2.Rf1+ Ke7 3.Nc4 Ng3+ 4.Ke5 Rxd5+ 5.Kxd5 Nxf1 6.Kc6 Nh2 7.Kxb6 Nxg4
8.Nxa5
    (0.93)   Depth: 9/18   00:00:08  397kN
1...Rd8 2.Nc4 Ne2 3.Ke3 Nd4 4.Nxb6 Re8+ 5.Kd3 Nxb3 6.d6
    (0.75)   Depth: 9/18   00:00:09  507kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2 4.d6 Nd4+ 5.Kg3 Rd8 6.Rd3 Rd7 7.Re3
    (0.66)   Depth: 10/21   00:00:16  857kN
1...Ne2 2.Rf1+ Ke7 3.Rf7+ Ke8 4.Rg7 Nc3+ 5.Kf5 Rxd5 6.Ke6 Kf8 7.Rxg5 Ke8
    (0.62)   Depth: 10/21   00:00:22  1280kN
1...Ne2 2.Rf1+ Ke7 3.Rf7+ Ke8 4.Rh7 Rf6 5.Nc4 Nd4 6.Ke5 Rf3 7.Nxb6 Re3+ 8.Kf6
Rxb3
    (1.06)   Depth: 11/23   00:00:46  2705kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2 4.Nxb6 Nd4+ 5.Kg3 Nxb3 6.d6 Nd4 7.Rf1+ Ke6 8.Re1+
Kf7 9.Rxe8 Kxe8
    (0.89)   Depth: 11/23   00:00:59  3438kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2 4.d6 Nd4+ 5.Kg3 Rd8 6.Rh1 Kg6 7.d7 Nxb3 8.Rb1 Nd4
9.Rxb6+
    (0.90)   Depth: 12/27   00:01:22  4772kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2 4.d6 Nd4+ 5.Kg3 Rd8 6.Rh1 Nxb3 7.Rf1+ Ke6 8.Rb1 Nd4
9.Rxb6
    (1.01)   Depth: 13/29   00:02:22  8091kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2 4.d6 Nd4+ 5.Kg3 Rd8 6.Rh1 Nxb3 7.Rb1 Nd4 8.Rxb6 Ke6
9.Rb7
    (1.01)   Depth: 14/31   00:04:23  15034kN




Uri



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