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Posts Tagged ‘Graz Defense’

The Limits of Computer Analysis… or Human Analysis?

Monday, January 4th, 2010

On Saturday I posted about an adventure I had in the Graz Defense. Chris Morgan and I played our game. When we reached move 9. Be3, the position looked like this:

After 9. Be3

After 9. Be3.

I briefly looked at my alternatives, but had pretty much committed to 9. …Bxe3 when I saw the Bishop would be coming at me with the d3 pawn move.

I ended up losing that game, but got the privilege of running over the game afterwards with Chris and Joe Alford. (Analysis with Joe is quite a treat – he’s about the strongest player in Bloomington, if not the strongest.)

The conclusion of Joe and Chris was that this was pretty much the penultimate strategic moment. All of us agreed that the Bishop trade didn’t look like the best move. Among other factors with the recapture White gets to have the f file opened for him, and the Black Queen’s post on f6 is even less secure than it was.

There are viable alternatives for Black (some of which I didn’t really explore as fully as I should have.) It’s a simple enough question: Take or defend. Defensive moves involving my Bishop included 9. …Bb6, 9. …Ba7, 9. …Bd6, 9. …d6. We pretty much decided that was the priority, as well.

So I come home, upload the game to my database and start looking at it. Although I believe in the soundness of our analysis, I called up my analysis engine on the position. And it eventually chose as it’s first line…. Bxe3!?

I went ahead and plugged in all of the candidate moves, and used all three chess engines I’ve installed to this computer to analyze the position to between 12 and 14 ply. Almost all the engines agreed on 9. …Bxe3. Here’s a table showing the various candidate moves and their positional evaluations:

Human or Computer: Which is right? Responses to 9. Be3
Computer responses are postition evaluation/search ply depth. Closer to zero in position evaluation is better for Black.
Move Crafty 20.14Fritz 6Rybka 2.2n2Human RankdB Game Notes
Bxe3.12/13.28/13.14/13Last/Worst
Bd6.71/13.34/12.39/13Second Choice
Bb6.46/13.50/14.25/14First ChoiceNote 1
Ba7.41/15.25/13.20/13Alternate/Equal to Bb6Note 2
d6.50/13.34/11.19/12Near prime, tied second maybe.Note 3
Note 1: ½-½ Pena Gomez,M-Espineira Gonzalez,P/Poio 2001
Note 2: 1-0 Judd,M-Harding,H/Cleveland 1871
Note 3: ½-½ Makarova,O-Kozhamberdin,B/Orsk 2000

Note: The full game, along with Rybka 2.2’s analysis of that position and some of my other notes can be found here.

Now, to be sure, Fritz 6 in the table above finds 9. …Ba7 just micro-fractionally the best choice. Yet the one game my database yielded to me shows a win for White after 9. …Ba7, too.

There are other limits here as well: Note that we are talking about ultra-fractional points of a pawn in advantage. (.14 = 14 hundrethds of a Pawn in equivalent material advantage. OK, in all fairness the numerical evaluation doesn’t have to equal the same points we would use in calculating material advantages. But it is close, and Fritz’s difference was .03, and Rybka’s difference between first and worst is .25 – that’s small!) If the programs were forced to make the move at the point I stopped their analysis, taking the Bishop would have been their route.

What to make of this?

On the one hand, this could be the stuff that a Grandmaster might take seriously. (GM wants a draw in a particular round in a tournament, so finds this line where a human playing White would presume Black will not exchange. Yet by making the Bishop trade Black manages to pull out a draw – though it would take much more analysis than I’ve given to one move to reach that conclusion.)

But on the other hand, it is equally one of those times when you recognize your own limits as a player. Which means it’s time to switch the computer off and switch on your brain. I still agree with my fellow humans: I should have played one of the alternate moves there.

(And, for potential nit-pickers, yes the advice might be: Don’t play the Graz Defense! ;) )

When you play OTB, it won’t be Fritz, Rybka, or Crafty playing your opponent. It will be you. If you ever reach this position as Black, do you take or do you defend? This is one of those times when you choose the line that will best help you….

….Enjoy your Chess!

“Graz” for the Lesson!

Saturday, January 2nd, 2010

A cold night, Chess game for analysis on the Computer, and the Blackhawks-Blues hockey game on TV. Could it be any better? :) Bonus: ‘Hawks are winning! :D

I’ve been very busy the last couple of days with this and that. Tomorrow morning a major Tools of the Trade / review on eNotate – been in various drafts for awhile, plus needing to get photos done.

I played one 20 minute game as Black this morning at Colley’s. It was a Ruy Lopez, Morphy Defense, that I continued into the Graz Defence. The Graz is a response to the Ruy Lopez that many scholastic and club players regard as cool, but isn’t as hot as it may look. (I didn’t know the name for it until some research this evening.)

The moves are: 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 b5 5.Bb3 Bc5. The position that results looks like this:

The Graz Defense

Graz Defense: 1. e4 e5 2. Nc3 Nf6 3. Bb5 a6 4. Ba4 b5 5.Bb3 Bc5

The 3. …a6 marks a Morphy Defense, named after Paul Morphy. It is called, “putting the question to the Bishop,” as the Bishop must either capture the Knight or retreat. This is fairly solid.

4. …b5 may look like a natural extension when the Bishop retreats to a4. “Hey, I put the question once, why not kick the Bishop again?” But when Black sidesteps with 5. Bb3, this puts the Bishop about where White would like it to be: Aiming square at the f7 pawn.

There can be some hope here, if Black can eventually shift the f3 Knight and then manage a c5-c4 pawn push, Black can smother White’s Bihsop. But Black has already lost one tempo in b5, and White has effectively gained a tempo from the Bishop dance.

Eventually I lose this game, but I can say “Gracias!” (or just “Graz!” ;) ) for the lesson I got in the game itself.

I also was able to postmortem this game with one of Bloomington’s strongest players and my opponent. There’s some more interesting things about the game I played, but I need to check with my fellow humans before committing to what I wrote up. (I may have misremembered something we analyzed… But since I was using eNotate to record the game, the notation of it was solid. :) )