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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