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

Author: Uri Blass

Date: 05:23:15 01/30/02

Go up one level in this thread


On January 30, 2002 at 08:08:18, Andrew Williams wrote:

>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?
>
>Are we sure that this blind spot is caused by null move? I tried switching
>off null move completely and it makes very little difference to what my program
>does in this position. My score still starts out at -1.something for black then
>goes to +1.something, then goes back to -1.something before drifting back up to
>around +0.9, all in the first 5 minutes of search (up to depth 20). Does anyone
>else find that null move doesn't make much difference here? Obviously using null
>move helps with the number of nodes, but it doesn't change the scores very much
>at all.
>
>Andrew

I am sure it is about null move.
It is not about the null move that you do.

It is about the special null move that Fritz does that is different than the
null move algorithm that most programs use.

Deep Fritz can see that Re6 has no threat so it simply does not analyze after
it.
I give Deep Fritz's analysis at the end of this post.


If your program analyze after Re6 inspite of the fact that it can see no threat
then it has different null move algorithm than Deep Fritz.

Note that after Re6 if it is black to move then black is losing.

I believe that the main line of Deep Fritz is simply Re6 null....

Fritz interface probably cannot show null moves in the main line so we do not
see it.

I checked Deep Fritz without null move and it has no problem to see the correct
evaluation.


New position
[D]8/8/1p1r1k2/p1pRN1p1/P3K1P1/1P6/8/8 b - - 0 1

Analysis by Deep Fritz:

1...Rxd5 2.Kxd5
  +-  (2.31)   Depth: 1/3   00:00:00
1...Re6
  +-  (2.69)   Depth: 8/15   00:00:00  4kN
1...Re6
  +-  (2.69)   Depth: 8/15   00:00:00  4kN
1...Re6
  +-  (2.69)   Depth: 8/15   00:00:00  4kN
1...Re6
  +-  (2.69)   Depth: 8/15   00:00:00  4kN
1...Re6
  +-  (2.69)   Depth: 8/15   00:00:00  4kN
1...Re6
  +-  (2.69)   Depth: 8/15   00:00:00  4kN
1...Re6
  +-  (2.69)   Depth: 8/15   00:00:00  4kN
1...Re6
  +-  (2.69)   Depth: 8/15   00:00:00  4kN
1...Re6
  +-  (2.69)   Depth: 8/15   00:00:00  4kN
1...Re6
  +-  (2.69)   Depth: 8/15   00:00:00  4kN
1...Re6
  +-  (2.69)   Depth: 8/15   00:00:00  4kN
1...Re6
  +-  (2.69)   Depth: 8/15   00:00:00  4kN
1...Re6--
  +-  (3.00)   Depth: 9/12   00:00:00  6kN
1...Re6--
  +-  (3.00)   Depth: 9/17   00:00:00  10kN
1...Re6!
  +-  (2.69)   Depth: 10/16   00:00:00  24kN
1...Re6--
  +-  (3.00)   Depth: 11/14   00:00:00  33kN
1...Re6--
  +-  (3.00)   Depth: 11/19   00:00:00  48kN
1...Re6!
  +-  (2.69)   Depth: 12/20   00:00:00  100kN
1...Re6--
  +-  (3.00)   Depth: 13/18   00:00:00  128kN
1...Re6--
  +-  (3.00)   Depth: 13/22   00:00:00  182kN
1...Re6--
  +-  (3.31)   Depth: 14/19   00:00:00  268kN
1...Re6--
  +-  (3.31)   Depth: 14/24   00:00:00  352kN
1...Re6--
  +-  (3.62)   Depth: 15/25   00:00:00  558kN
1...Re6--
  +-  (3.62)   Depth: 15/26   00:00:01  767kN
1...Re6!
  +-  (3.31)   Depth: 16/28   00:00:02  1585kN, tb=1
1...Re6--
  +-  (3.62)   Depth: 17/27   00:00:03  2460kN, tb=2
1...Re6--
  +-  (3.62)   Depth: 17/30   00:00:05  3277kN, tb=2
1...Re6--
  +-  (3.94)   Depth: 18/29   00:00:08  5510kN, tb=4
1...Re6--
  +-  (3.94)   Depth: 18/33   00:00:13  8616kN, tb=6
1...Re6--
  +-  (4.25)   Depth: 19/30   00:00:21  14184kN, tb=15
1...Re6--
  +-  (4.25)   Depth: 19/34   00:00:28  18812kN, tb=28
1...Re6!
  +-  (3.94)   Depth: 20/34   00:01:03  43098kN, tb=122
1...Re6--
  +-  (4.25)   Depth: 21/36   00:01:44  69910kN, tb=190
1...Re6--
  +-  (4.25)   Depth: 21/38   00:02:42  109188kN, tb=453
1...Re6--
  +-  (4.56)   Depth: 22/37   00:04:16  175277kN, tb=689

(Blass, Tel-aviv 30.01.2002)

Uri



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