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

Author: Miguel A. Ballicora

Date: 15:13:47 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?

It depends on the implementation, I guess. Gaviota uses nullmove but it
has no problem to see that Re6 is not winning for white and soon it sees
that it is good for black by a small margin. In other words, it sees that the
knight falls. Gaviota does not prune after nullmove, it reduces depth.
So, zugswang problems are delayed only 2 plies.
I bet that YACE performs well in this position. Dieter explains some time ago
that it has a way to control it, that will be similar to Gaviota's.

The best position to try I think is this:

[D]8/8/1p1r1k2/p1pPN1p1/P3KnP1/1P6/8/3R4 w - - bm Nxd5;

Gaviota's analysis:

+-----------------+
| . . . . . . . . |
| . . . . . . . . |
| . x . r . k . . |
| x . x o N . x . |
| o . . . K n o . |
| . o . . . . . . |
| . . . . . . . . |
| . . . R . . . . |
+-----------------+

Analyze
move_entered: <EMPTY>
Error {unknown command}: Analyze
analyze
        25   1:      0.0    +0.11  Rd6-d8
       521   2:      0.0    -0.13  Nf4-e2   Rd1-d3
      1245   3:      0.0    -0.08  Rd6-d8   d5-d6    Rd8-e8
      2143   4       0.0    -0.08  Rd6-d8   Rd1-h1   Nf4xd5   Rh1-h6
                                   Kf6-g7   Rh6-g6   Kg7-h7   Rg6xg5
      2304   4:      0.0    -0.08  Rd6-d8   Rd1-h1   Nf4xd5   Rh1-h6
                                   Kf6-g7   Rh6-g6   Kg7-h7   Rg6xg5
      4463   5       0.1    -0.09  Rd6-d8   Ne5-c4   Rd8-b8   d5-d6
                                   Rb8-e8   Ke4-f3
      7996   5:      0.1    -0.09  Rd6-d8   Ne5-c4   Rd8-b8   d5-d6
                                   Rb8-e8   Ke4-f3
     13848   6       0.1    -0.08  Rd6-d8   Rd1-h1   Nf4xd5   Rh1-h6
                                   Kf6-g7   Rh6-g6   Kg7-h7   Rg6xg5
                                   <EMPTY>  <-transp
     19745   6:      0.2    -0.08  Rd6-d8   Rd1-h1   Nf4xd5   Rh1-h6
                                   Kf6-g7   Rh6-g6   Kg7-h7   Rg6xg5
                                   <EMPTY>  <-transp
     33018   7       0.3    +0.00  Rd6-d8   Ne5-c4   Rd8-e8   Ke4-f3
                                   Re8-h8   Kf3-e4   Rh8-e8
     42578   7:      0.4    +0.00  Rd6-d8   Ne5-c4   Rd8-e8   Ke4-f3
                                   Re8-h8   Kf3-e4   Rh8-e8
     96173   8       0.9    +0.04  Rd6-d8   Ne5-c4   Rd8-e8   Ke4-f3
                                   Nf4-e2   Rd1-d3   Ne2-d4   Kf3-g2
                                   Re8-b8   Rd3-h3
    117458   8:      1.1    +0.04  Rd6-d8   Ne5-c4   Rd8-e8   Ke4-f3
                                   Nf4-e2   Rd1-d3   Ne2-d4   Kf3-g2
                                   Re8-b8   Rd3-h3
    165897   9       1.5    +0.02  Rd6-d8   Ne5-c4   Rd8-e8   Ke4-f3
                                   Nf4-e2   Rd1-d3   Ne2-d4   Kf3-g2
                                   Re8-b8   Rd3-h3   Kf6-e7   Rh3-h7
                                   Ke7-f6
    261939   9:      2.4    +0.02  Rd6-d8   Ne5-c4   Rd8-e8   Ke4-f3
                                   Nf4-e2   Rd1-d3   Ne2-d4   Kf3-g2
                                   Re8-b8   Rd3-h3   Kf6-e7   Rh3-h7
                                   Ke7-f6
    567511  10       5.2    -0.02  Rd6-d8   Ne5-c4   Rd8-e8   Ke4-f3
                                   Nf4-e2   Rd1-f1   Kf6-g7   Nc4xb6
                                   Ne2-d4   Kf3-g2   Re8-e2   Rf1-f2
                                   Re2xf2   Kg2xf2   Nd4xb3
    917542  10:      8.4    -0.02  Rd6-d8   Ne5-c4   Rd8-e8   Ke4-f3
                                   Nf4-e2   Rd1-f1   Kf6-g7   Nc4xb6
                                   Ne2-d4   Kf3-g2   Re8-e2   Rf1-f2
                                   Re2xf2   Kg2xf2   Nd4xb3
   1940657  11      18.1    -0.13  Rd6-d8   Ne5-c4   Rd8-e8   Ke4-f3
                                   Nf4-e2   Nc4xb6   Ne2-d4   Kf3-f2
                                   Nd4xb3   Rd1-d3   Nb3-c1   Rd3-c3
                                   Re8-e2   Kf2-f3   <EMPTY>  <-transp
   6014668  11      56.5    +0.13  Nf4xd5   Rd1xd5   Rd6-e6   Ke4-f3
                                   Re6xe5   Rd5-d6   Re5-e6   Rd6xe6
                                   Kf6xe6   Kf3-e4   Ke6-e7   Ke4-f5
                                   Ke7-d6   Kf5xg5   Kd6-e5
   6102322  11:     57.4    +0.13  Nf4xd5   Rd1xd5   Rd6-e6   Ke4-f3
                                   Re6xe5   Rd5-d6   Re5-e6   Rd6xe6
                                   Kf6xe6   Kf3-e4   Ke6-e7   Ke4-f5
                                   Ke7-d6   Kf5xg5   Kd6-e5
  11085576  12     104.1    +0.15  Nf4xd5   Rd1xd5   Rd6-e6   Ke4-f3
                                   Re6xe5   Rd5-d6   Re5-e6   Rd6xe6
                                   Kf6xe6   Kf3-e4   Ke6-e7   Ke4-f5
                                   Ke7-d6   Kf5xg5   Kd6-e5   Kg5-g6

The pv is crappy because Gaviota does not understand Pawn
endgames.

Miguel






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