Double-checking your opening - part two

DOUBLE-CHECKING YOUR OPENING -- PART TWO

by Steve Lopez

This involves using an often overlooked program feature: "Explain all moves". It's often passed over (or even derided) as a "beginner's feature", but it actually has other uses besides a means of getting very cursory move information.

Going back to our example game from the previous column, you'll remember that White was the first player to leave "book" having done so at move thirteen. Let's load the game into the Fritz interface and click on Black's twelfth move (the move just prior to the point at which White varied from established theory). You may recall that White's variance was the move 13.Nxd5. Let's fire up the "Explain all moves" feature and see where that move appears in the list of all legal moves:

Keep an eye on the information bar at the bottom of the screen; at some point it's going to say "Done -- Explain All Moves". Then take a look at where the move you (or your opponent) played actually ranks on the list. You see, "Explain all moves" shows the chess engine's move preferences in order from best (at the top of the list) to worst (at the bottom). Remember that we're not after the text explanations here -- we just want to see where the move that was actually played ranks on the list. After a ten ply search, the chess engine thinks that 13.Nxd5 is the third-best move and that either 13.e6 or 13.Qe2 were better moves (and, in light of this, it's not too surprising that those were the only two "book" moves we discovered in the opening tree of established theory).

Now this is just a cursory analysis (it would be better to get a search depth somewhere in the teens -- and we'll do this in a moment using ChessBase 9) but it's provided us with some important clues about our choice of 13.Nxd5. It's now up to us to look at the board position and determine why those two other moves were better. The software won't do this for you -- you'll need to look at the alternative moves and figure out their benefits (and, as a cursory analysis of my own, the immediate 13.e6 threatens the d7-Knight as well as threatens to disorganize Black's Kingside pawns even worse than is already the case, while 13.Qe2 supports the e-pawn's advance and puts pressure on Black's King which is still stuck on the e-file).

We've seen two ways to use the Fritz interface to get more information about the point at which one player veered away from known theory. Now let's fire up ChessBase 9 and look at some more techniques.

Load the game in question by double-clicking on it. Next you'll want to go to the Window menu, select "Panes", and then choose "Extra book pane" from the submenu. You'll want to resize the panes to get a comfortable viewing area for the board and both the Notation and Book panes:

Now we're going to assume that our last two tips (performed in the Fritz interface) never happened and that we're starting out "cold" on this project. Our first step is to determine the point at which one of the players left "known theory". This is pretty easy to do. Just use the VCR buttons below the chessboard or the cursor keys on your keyboard to step through the game a move at a time. Keep an eye on the opening book pane as you do this and it'll be easy to spot the point at which one of the players made a "non-book" move:

Check it out -- as soon as 13.Nxd5 was played, the opening book pane went blank. This tells us that 13.Nxd5 was the point at which one player (White in this case) went "out of book".

Note that this method is more labor-intensive than the "quick and dirty" method we used in the previous ChessBase Workshop column (in which we used the game analysis features to point out the "last book move"). But there are some solid benefits to this method -- as you're stepping through the moves and watching the opening book pane you can see some great statistical information at each point along the way: the number of times various moves occurred in practical play as well as their statistical success rates. This will give you an idea of where your (and your opponent's) moves ranked within the realm of known theory. It might also give you some good ideas about how you might play the opening differently the next time around.

We've now established that the "critical point" in the opening of this game occurred when Black played 12...exf5 and White varied from known theory on his next move. So let's mark 12...exf5 as a "critical position". Right-click on that move and select "Special annotation" from the popup menu, then "Critical opening position" from the submenu. This will color the move 12...exf5 in blue to serve as a reminder that this was the last "book" move played in the game. Be sure to use "Replace game" to save this change (if you want to do so).

When we clicked on 12...exf5, the opening book pane changed to show us White's "book" responses to that move:

There are two responses listed: 13.e6 and 13.Qe2: one game was a White win, the other was a victory for Black. It's really important to note here that statistics don't tell the whole story. The final result of the two games may or may not be directly dependent on White's choice at move thirteen (but it's a pretty safe bet that they weren't). The only way to be sure is to actually look at the two games in question.

How do we find them? That's easy. With the move 12...exf5 highlighted, click on an empty spot in the opening book pane (e.g. not on one of the listed moves) and select "Search games" from the popup menu. You'll see the Notation pane automatically switch to the "Reference" tab display. ChessBase 9 will now search your reference database (which we learned how to designate in the previous column) and provide a list of games containing the board position after 12...exf5:

Now the first thing that you'll notice is that the search found three games instead of the expected two. Why? You'll remember that we loaded Mega Database 2005 as our reference database; this isn't the same database from which our opening book (Powerbook 2005) was created -- there are more games in Mega 2005 than in the Powerbook database. So that's why we have an extra game displayed in the search results list.

Now that we've done the search, we can play through these three games and see exactly how they played out. Take your time when you play through them and think about the moves. All of this will increase your understanding of the positions that follow Black's choice of 12...exf5.

One of the really neat things you can do with these games is to merge them together by dragging and dropping. Open your game and one of the reference games in separate windows, use Window/Arrange/--- to place the games side by side, and then drag and drop the reference game onto your game. Do this for each of the reference games, use "Replace game" to save the work, and you now have a sort of "annotated" (really "opening referenced") version of your game:

Earlier in this article we looked at using "Explain all moves" in the Fritz interface to show you how your chosen move ranked in the "opinion" of a chess engine. You can do something similar in ChessBase 9. Using our example game, we'd click on 12...exf5 to highlight it, then fire up our default chess engine in "Infinite analysis" mode (the engine will analyze until we stop it). In this case, it's best to let the engine reach a double-digit search depth, as well as an odd number of plies in the depth (because some chess engines get somewhat tactically "blind" at even numbers of plies). Use the "plus" buttons to increase the number of variations displayed.

Just as with "Explain all moves", the engine pane will display the variations ranked in order of preference from best to worst:

You'll notice in the illustration that the "Depth" value reads "12" -- which is not an odd number. No, I didn't make a mistake. I allowed the chess engine to complete the eleventh ply; since ply eleven was finished, the display naturally incremented to a value of "12".

We notice that White's thirteenth move (13.Nxd5) ranks as second on the engine's list of preferred moves. So it's possible that the move isn't "bad" -- it's just not "book". Now that we've made this determination, we can easily pop the engine's analysis into the gamescore. Right-click in the engine pane and select the command "Copy all to notation" from the popup menu. The engine's variations will be inserted into the gamescore:

There are lots of other ChessBase 9 features that we could also use in our research, such as "Opening report" and "Find novelty". But these two columns (last week's and this one) should give you plenty of ideas on how to "double-check" your opening move choices. We've learned how to identify the point at which one player "left book" and, more importantly, how to pull up extra games from a database and additional information from a chess engine that will help to increase our understanding of the positions that arise from the "book" moves as well as our "non-book" choice.

Chess games are seldom won or lost in the opening, but our choices in that stage of the game can certainly affect our middle- and endgames. Taking a closer look at those choices, and at the choices stronger players have made, can help us make better opening move selections, increase our understanding of the ideas behind the openings we play, and hopefully help us to improve our results.

Until next week, have fun!

© 2005, Steven A. Lopez. All rights reserved.