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Very Hot Topic (More than 25 Replies) My trusty engine tells me Chess Truth (Read 48959 times)
Zwischenzugzwang
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Re: My trusty engine tells me Chess Truth
Reply #31 - 11/26/11 at 19:39:51
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It's easy to dismiss computers as they don't understand appr. one zillion positions, but sometimes they are not so bad. I have one question for the engine specialists in this forum:

In his new book "Understanding Chess Middlegames", John Nunn writes in the foreword (p. 7):

Quote:
(...) I first analysed the examples in depth with computer assistance (Deep Fritz, Deep Rybka and the free engine Houdini, depending on the type of position) and used this analysis as a basis for my general description of the course of the game (...) (my highlighting)


Which engine would you use for what type of position?

Thanks in advance, and best regards,

Zwischenzugzwang
  

What do people mean when they say "Chess is the pawn of the soul"?
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Vass
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Re: My trusty engine tells me Chess Truth
Reply #30 - 11/22/11 at 07:51:19
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I think the engine's program is written economically in a way that can be described as "following the principles".. In this special case (promoting to bishop) the engine is told to consider promoting to B (instead of to queen) only if the opponent is entering into a stalemate right after a direct queen promotion. And if not a stalemate right after the promotion then a new-promoted queen is considered to be better than a new-promoted bishop, which in most of the cases (maybe 99.9 %) is true. A problem arises in this particular case when (in 0.01% maybe) a special position like this one is arranged. Anyway, I still can't figure how the strength of the engine is affected by this arrangement of the engine's "thinking process".. Maybe these + ELO points are gained because of the fact that this particular engine is "thinking" faster in some positions than the other engines which are not modified by this rule.. Who knows? Only the engine programmers maybe..  Cool
  
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Zwischenzugzwang
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Re: My trusty engine tells me Chess Truth
Reply #29 - 11/22/11 at 06:06:51
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Markovich wrote on 11/22/11 at 01:22:39:
I suspect the cost of refusing to calculate bishop promotion other than in technical endings is very slight.


But how else would ignoring a possibility increase the playing strength (assuming that this is really the consequence of not considering this sort of underpromotion)?
  

What do people mean when they say "Chess is the pawn of the soul"?
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Markovich
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Re: My trusty engine tells me Chess Truth
Reply #28 - 11/22/11 at 01:22:39
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As I recall there are one or two technical endings wbere poromotion to bishop figures in. But here Rybka no doubt relies on tablebases (so that she does indeed "recognize" this possibility). I suspect the cost of refusing to calculate bishop promotion other than in technical endings is very slight.
  

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Zwischenzugzwang
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Re: My trusty engine tells me Chess Truth
Reply #27 - 11/21/11 at 06:03:31
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So the ignorance of the "bishoping" rule was intended? And that was done to gain some rating points (probably by cutting down the resulting trees a little bit)? Funny if it works.

Chess coaches of the world, please pay attention to this!
Teach your students that a pawn is not allowed to promote to a bishop!!
   Wink

In this particular case, it doesn't spoil the problem, as, because of its symmetry, the bishop promotion is only relevant if Black is promoting to a bishop too. As Rybka doesn't see this possibility, it doesn't need to take bishoping into account for White either.

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Zwischenzugzwang
  

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Vladimir
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Re: My trusty engine tells me Chess Truth
Reply #26 - 11/21/11 at 03:20:15
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Zwischenzugzwang wrote on 11/19/11 at 09:21:17:
A little oddity:

Chessbase shows (in "Kavalek in Huffington: Joys of Chess: From Krabbé to Hesse") the following problem:

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(Leonid Yarosh - White mates in 4 moves, Shakhmaty v SSSR, 1983 [GM Lubomir Kavalek/Huffington Post])

The point is, that, after 1.a7!, whichever piece Black promotes his pawn to, White mates within the given number of moves by promoting to the same piece.

Of course, every chess engine (I tested Fritz 11, Hiarcs 13, Houdini 1.5, Stockfish 2.0.1) solves the problem in a fracture of a second. Oddly enough, only Rybka (all versions I have) has a problem with the variation 1...axb1B: It doesn't find the solution 2.axb8B. Does Rybka have a blind spot and doesn't know the underpromotion to a bishop?  Smiley

Best regards,

Zwischenzugzwang


It's well-known that Rybka does not iterate bishop underpromotions in its search. It will allow them as legal moves if played against it, but it will not search them in its tree.

Despite a fair bit of flak from the community, apparently Rajlich's ultra-pragmatic design choice reportedly gained 2 or 3 Elo points from the reduction.

From a consumer viewpoint, the gain is negligible, and there's something not very aesthetic about an engine being entirely unable to solve a problem even if it searched until the end of time just because it didn't fully support the rules of chess. Nevertheless, it is true that bishop underpromotions are sufficiently rare that one could say they pretty much only exist in contrived positions.

At any rate, it is what it is.
  
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Vass
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Re: My trusty engine tells me Chess Truth
Reply #25 - 11/19/11 at 12:14:07
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Very interesting!.. Maybe Rybka doesn't know that white can promote the pawn into a third bishop?!?  Huh
  
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Zwischenzugzwang
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Re: My trusty engine tells me Chess Truth
Reply #24 - 11/19/11 at 09:21:17
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A little oddity:

Chessbase shows (in "Kavalek in Huffington: Joys of Chess: From Krabbé to Hesse") the following problem:

* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
*
(Leonid Yarosh - White mates in 4 moves, Shakhmaty v SSSR, 1983 [GM Lubomir Kavalek/Huffington Post])

The point is, that, after 1.a7!, whichever piece Black promotes his pawn to, White mates within the given number of moves by promoting to the same piece.

Of course, every chess engine (I tested Fritz 11, Hiarcs 13, Houdini 1.5, Stockfish 2.0.1) solves the problem in a fracture of a second. Oddly enough, only Rybka (all versions I have) has a problem with the variation 1...axb1B: It doesn't find the solution 2.axb8B. Does Rybka have a blind spot and doesn't know the underpromotion to a bishop?  Smiley

Best regards,

Zwischenzugzwang
  

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Vass
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Re: My trusty engine tells me Chess Truth
Reply #23 - 11/15/11 at 11:13:44
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Engines good at tactics.. Really?

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If you're tired of looking at your engines' solutions 1.Kh1 (1.Kh2) or 1.f3 as the superior moves for white in this position...just try to wake up your beloved engine with 1.Bxh6!   Shocked Then after the obvious 1...gxh6 2.Qxh6 Ng6 (the knight on h4 was hanging badly) it usually starts counting on 3.Nf5  Roll Eyes  But enter 3.Re1! and...whoa, suddenly your machine is seeing everything.  Cheesy
  
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trw
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Re: My trusty engine tells me Chess Truth
Reply #22 - 11/03/11 at 19:46:17
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Markovich wrote on 11/03/11 at 16:48:54:
trw wrote on 11/03/11 at 14:08:56:
one of my favorite games is still this: http://www.chessgames.com/perl/chessgame?gid=1048284
A game which computers still don't understand the forced win for white. It came up as a 'test your strength' puzzle on chessgames.com Everyone cheated and declared the position drawn by writing down their computer's analysis. While Shirov did  not play the best defense, the game is heavily analyzed by Gelfand in his 300 best games book. All the computer moves are refuted by Gelfand's analysis to wins. No draw!

But is that true? The last comments on your link seem to suggest that Black draws after all. I haven't looked much at the chess of it.

Nope, white wins no matter what. The commentators on the game as I said are believing their chess engine -- which was the point of this thread.
  
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Re: My trusty engine tells me Chess Truth
Reply #21 - 11/03/11 at 16:48:54
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trw wrote on 11/03/11 at 14:08:56:
one of my favorite games is still this: http://www.chessgames.com/perl/chessgame?gid=1048284
A game which computers still don't understand the forced win for white. It came up as a 'test your strength' puzzle on chessgames.com Everyone cheated and declared the position drawn by writing down their computer's analysis. While Shirov did  not play the best defense, the game is heavily analyzed by Gelfand in his 300 best games book. All the computer moves are refuted by Gelfand's analysis to wins. No draw!

But is that true? The last comments on your link seem to suggest that Black draws after all. I haven't looked much at the chess of it.
  

The Great Oz has spoken!
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Re: My trusty engine tells me Chess Truth
Reply #20 - 11/03/11 at 15:53:26
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And look at this one! Aronian - Volokitin:

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After the game Aronian makes the remark: Bxh6! with excellent play for white.
Just try to give this to Houdini!..  Cheesy
Never trust your engine!.. Trust your mind!..  Lips Sealed
  
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Re: My trusty engine tells me Chess Truth
Reply #19 - 11/03/11 at 15:08:16
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First one 1 Re2(?)!! Second one 1 Kd1, "+25.94" ...
  
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Vass
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Re: My trusty engine tells me Chess Truth
Reply #18 - 11/03/11 at 14:54:39
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The same thing, but little exaggerated:
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Shocked
  
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Vass
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Re: My trusty engine tells me Chess Truth
Reply #17 - 11/03/11 at 14:47:30
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[quote author=6D6E6462030 link=1319957182/16#16 date=1320330168]My Houdini is weird! In the first position it plays 1 ...Qh6, giving it as winning and making me think it's [i]possible[/i] it's gone for this having evaluated it as actually stronger than 1 ...g3 2 h3 Bh3. Then, if I input 1 ...g3 it then sees 2 h3 Bh3 immediately (playing 2 hg in fact), but when I input 2 h3 as well, it plays 2 ...Nc8. Weird! ...[/quote]
  ;D
A paradox:
[fen]8/8/2k5/5p2/p1p1pPp1/PpPpP1Pp/1P1P3P/QNR1RNK1 w - - 0 13



[/fen]
If you put this position to Houdini...what evaluation do you think it gives? (Suppose the last black move is b4-b3..) From +4.0 (for Qa1-a2) to +25.0 or so..  :D
  
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