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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