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Subject: Re: So is this a BUG in Fritz 7b?

Author: Uri Blass

Date: 13:06:39 01/31/02

Go up one level in this thread


On January 31, 2002 at 15:26:40, Roy Eassa wrote:

>On January 31, 2002 at 15:19:16, Uri Blass wrote:
>
>>On January 31, 2002 at 12:41:11, Roy Eassa wrote:
>>
>>>On January 30, 2002 at 18:52:06, Vincent Lejeune wrote:
>>>
>>>>On January 30, 2002 at 18:07:38, Chessfun wrote:
>>>>
>>>>>On January 30, 2002 at 17:18:21, Roy Eassa wrote:
>>>>>
>>>>>>On January 29, 2002 at 16:13:45, Roy Eassa wrote:
>>>>>>
>>>>>>>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
>>>>>>
>>>>>>Re: So is this a BUG in Fritz 7b -- something that should be fixed?  Something
>>>>>>that could easily be fixed without negatively impacting anything else to any
>>>>>>measurable degree?
>>>>>
>>>>>
>>>>>Not just Fritz 7b, infact most Fritz versions see white clearly winning.
>>>>>
>>>>>Sarah.
>>>>
>>>>Yes, simply because :
>>>>1)white is in zugzwang
>>>>and
>>>>2)Fritz use null-move
>>>>and both are not compatible with each other.
>>>
>>>
>>>But other programmers' engines use null move and they do NOT have the same
>>>problem with this position (due to refinements in their null move handling, as I
>>>understand it).
>>>
>>>Thus this is essentially a Fritz BUG that can be fixed, thereby making Fritz
>>>stronger (IMO).
>>
>>No it is not.
>>It is a design decision of the Fritz programmers to use slightly different null
>>move algorithm.
>>
>>many of the other programs also blunder before this move and Crafty blundered in
>>the game because of it's null move algorithm.
>>
>>Uri
>
>
>I have never seen a position where a move immediately wins a piece and changes
>the evaluation from -5 to +1, yet a top program cannot see it.
>
>Until now.
>
>That should be classified as a bug, IMHO.



Here is an anlaysis of shredder 2 plies before on p200
Shredder5.32 cannot see the winning material move except depth 1 when shredder
believes that Nxd5 is losing a piece.

It is not winning a piece but I am almost sure that it is possible to change the
position such that shredder is going to miss winning a piece.

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

Analysis by Shredder 5.32:

1...Rxd5 2.Rxd5 Ne2 3.Rxc5 bxc5 4.Nd7+
    (0.83)   Depth: 1/2   00:00:00
1...Rxd5 2.Rxd5 Nxd5 3.Kxd5 c4
  +-  (2.10)   Depth: 1/2   00:00:00
1...Rxd5 2.Rxd5 Nxd5 3.Kxd5 c4
  +-  (3.80)   Depth: 1/2   00:00:00
1...Nxd5 2.Rxd5 Re6 3.Kd3 Rxe5 4.Rd6+ Re6 5.Rxe6+ Kxe6 6.Ke4 Kd6 7.Kf5 b5 8.axb5
c4 9.bxc4 a4 10.Kxg5
  +-  (3.50)   Depth: 1/2   00:00:00
1...Nxd5 2.Rxd5 Re6 3.Kd3 Rxe5 4.Rd6+ Re6 5.Rxe6+ Kxe6 6.Ke4 Kd6 7.Kf5 b5 8.axb5
c4 9.bxc4 a4 10.Kxg5
  +-  (3.50)   Depth: 1/2   00:00:00
1...b5 2.axb5 a4
  +-  (2.31)   Depth: 1/2   00:00:00
1...b5 2.axb5 a4
  +-  (1.76)   Depth: 1/2   00:00:00
1...b5 2.axb5 a4
  +-  (1.76)   Depth: 1/2   00:00:00
1...Ke7 2.Nc4 Rh6
    (0.60)   Depth: 1/2   00:00:00
1...Ke7 2.Nc4 Rh6
    (0.83)   Depth: 1/2   00:00:00
1...Ke7 2.Rd3
    (0.79)   Depth: 2/4   00:00:00
1...Ke7 2.Nc4 Nh5 3.gxh5 Rd8
    (1.05)   Depth: 3/6   00:00:00
1...Ke7 2.Nc4 Rh6
    (1.35)   Depth: 3/6   00:00:00
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2
    (0.83)   Depth: 3/6   00:00:00
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2
    (0.83)   Depth: 3/6   00:00:00
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2
    (0.83)   Depth: 4/8   00:00:00
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2
    (0.83)   Depth: 5/10   00:00:00
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2
    (0.83)   Depth: 6/12   00:00:00
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2
    (0.83)   Depth: 7/14   00:00:00  1kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2
    (0.83)   Depth: 8/16   00:00:00  2kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2
    (0.83)   Depth: 9/18   00:00:00  3kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2
    (0.83)   Depth: 10/20   00:00:01  4kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2
    (0.83)   Depth: 11/22   00:00:01  5kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2
    (0.83)   Depth: 12/24   00:00:01  7kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2
    (0.83)   Depth: 13/25   00:00:01  11kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2 4.Nxb6 Nd4+ 5.Kf2 Re2+ 6.Kf1
    (0.78)   Depth: 14/26   00:00:26  770kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2 4.Nxb6 Nd4+ 5.Kf2 Re2+ 6.Kf1 Re4 7.Nd7+ Ke7 8.Nxc5
Rxg4 9.Kf2 Kd6
    (0.70)   Depth: 15/27   00:01:43  3473kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2 4.Nxb6 Nd4+ 5.Kf2 Ke7 6.Re1+ Kd8 7.Rxe8+ Kxe8 8.Ke3
Nxb3 9.Kd3 Ke7
    (0.79)   Depth: 16/28   00:04:45  9204kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2 4.Nxb6 Nd4+ 5.Kf2 Re2+ 6.Kf1 Re4 7.Nd7+ Ke7 8.Nxc5
Rf4+
    (0.80)   Depth: 17/29   00:10:16  22197kN
1...Rd8 2.Nc4 Re8+ 3.Kf3 Ne2 4.Nxb6 Nd4+ 5.Kf2 Re2+ 6.Kf1 Re4 7.Nd7+ Ke7 8.Nxc5
Rf4+
    (0.72)   Depth: 18/30   00:23:32  48689kN
1...Rd8 2.Rh1 Nxd5 3.Rh6+ Kg7 4.Rg6+ Kf8 5.Re6 Nc3+ 6.Kf5 b5 7.axb5 Nxb5 8.Kxg5
Nd4 9.Rb6 Ke7
    (0.70)   Depth: 19/31   01:25:41  188426kN
1...Rd8 2.Rh1 Nxd5 3.Rh6+ Kg7 4.Rg6+ Kh7 5.Re6 b5 6.axb5 Nc3+ 7.Kf5 Nxb5 8.Kxg5
Nd4 9.Re7+ Kg8 10.Rb7 Rf8
    (0.83)   Depth: 20/32   02:29:33  331868kN
1...Rd8 2.Rh1 Nxd5 3.Rh6+ Kg7 4.Rg6+ Kf8 5.Nc4 Nc3+ 6.Kf5 b5 7.axb5 Nxb5 8.Kxg5
Rd5+ 9.Kf6 Rd3 10.Nxa5 Nd4
    (0.85)   Depth: 21/33   04:49:30  638246kN
1...Rd8 2.Rh1 Nxd5 3.Rh6+ Kg7 4.Rg6+ Kh7 5.Re6 b5 6.axb5 Nc3+ 7.Kf5 Nxb5 8.Re7+
Kg8 9.Nd7 Nd4+ 10.Kg6 c4 11.bxc4 Ne6
    (0.92)   Depth: 22/34   09:07:25  1191993kN
1...Rd8 2.Rh1 Nxd5 3.Rh6+ Kg7 4.Rg6+ Kf8 5.Nc4 Nc3+ 6.Kf5 b5 7.axb5 Nxb5 8.Kxg5
Nd4 9.Rb6
    (1.05)   Depth: 23/35   25:17:48  3275496kN




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