ChessBase and Correspondence chess -- part 5

Trees have been discussed at length in past columns; I'll mention a few points first as a quick refresher. An opening tree is simply a means of looking at a whole lot of games at one time (since the games are merged together) with the additional benefit of a "bean count" which provides success/failure statistics for each move in the tree.

There are three ways to generate an opening tree. We've already seen one of these: a tree is created as part of the Opening Report process (in fact, many sections of the opening report are derived from that tree; it's essentially the same material presented in a different organizational manner). A second way is to generate a tree "on the fly", creating a temporary tree (one which disappears back into the ether as soon as you close the tree's window).

The first step in creating a temporary tree is to highlight a bunch of games from a list. This might be a database's game list, the Clipboard, or a search results window. The simplest way to select every game in a list is to single-click on the first game in the list (to highlight it) and then hit CTRL-A on your keyboard; this will highlight every game in that list (even the ones you can't see until after you've scrolled the list down). Then you hit SHIFT-ENTER to start the process of creating a tree from those games. (If there are a lot of games in the list [i.e. thousands] you may receive a "confirmation dialogue" asking if you wish to proceed; just click "OK" to continue the process). How long will it take? That depends, of course, on the number of games and the speed of your processor; it takes sixty to ninety seconds to create a temporary tree from about twenty-five thousand games on my relatively slow PIII 800 MHz machine.

And please do note the use of the word "temporary" when describing this tree; as soon as you close the tree's window, it's gone.

That point brings us to the third method of creating a tree. You can create a permanent tree; it's "permanent" in the sense that it still exists on your hard drive when you exit the tree, but you can always delete it later if you wish. The first step in creating the tree is to make an empty tree somewhere on your hard drive. In the main database screen in ChessBase (the window that shows icons for your databases), go to the File menu, select "New", and then "Database" from the submenu.

Now it gets a wee bit tricky. Click the black arrow button at the righthand side of the "Save as Type" field, then be sure to select "Books (*.CTG)" from the pulldown list of file types (you might recall from past columns that we use the terms "opening tree" and "opening book" interchangably). Name your tree whatever you choose and select the folder in which it will reside (refer to the previous column in this series in which we created a game database; the processes are practically identical), then click the "Save" button to save the new empty tree:

A new icon will appear in your database window and will already possess a "tree" symbol (ChessBase recognizes that a .CTG file is an opening book/tree and it automatically attaches the "tree" picture to the icon):

Now one big question remains: how are we going to get games into this tree? As always with ChessBase, there's more than one way to skin a cat. You can take any list of games, hit CTRL-A to highlight the list, right-click on any of the highlighted games, then select "Edit" and "Copy" from the popup menu/submenu. Then you can right-click on the icon for your empty tree, and select "Edit" and "Paste" from the popup menu/submenu. Or, if you've created a database of just the games that are relevant to your game's opening, you can just drag and drop the database's icon onto the icon for the new opening tree.

In either case, you'll get the following dialogue:

This allows you more control over the tree's contents than if you'd created a temporary tree "on the fly". You get to choose a span of the database's games to merge into a tree (the defaults are "1" and the highest-numbered game in the database). You can also choose a "cut off" value for the length of lines/variations in the tree; note that this number is given in plies or "half-moves", so the default value of "20" results in lines that are ten moves long for each player (but see the next paragraph).

Also note that you have a choice between "Absolute length" and "ECO relative length". Absolute length means that each variation will be cut off at the same point; the default value of "20" means that every variation in the tree will be ten moves long. If you select ECO relative length, main line variations will likely be longer than whatever you set as the default length, while seldom-played sidelines will often be shorter than your chosen default length. Using an Alekhine Defense database (referring back to our example game from previous columns in this series) and selecting "ECO relative" with a default length of "20" gave me some main line variations that were nearly sixty plies long (three times the default value I'd selected) because they contained frequently-played "known" theory (ergo, it was important for me to be aware of these moves).

A last toggle lets you include variations from annotated database games in the tree. Although such variations won't be considered for statistical purposes, they'll still appear as possible candidate moves as you step through the tree.

After you've made your selections, click "OK" and ChessBase will create the tree for you. Once again the length of time required will be dictated by your processor speed, the number of games you're merging together, the length and type you've selected for the lines to be included, and whether or not you've opted to add variations to the tree. In all cases of tree creation (temporary and permanent), you'll see a progress bar dialogue appear on your screen:

The only reason to ever use the "Stop" button would be if you suddenly realize that you've bit off more than you can chew: you're trying to merge too many games on too slow a computer and it's going to take an eon or three to complete the process. That's when you'll want to click "Stop"; otherwise just let the process rock on to full completion.

I received an interesting e-mail from a ChessBase user a few weeks ago. He inquired about dragging and dropping new games into an existing tree: "How do I know whether or not any of the games are duplicates of games already in the tree?" Answer: you don't. So I recommend deleting the old tree and creating a new one later after adding the new games to your database and then eliminating duplicates on the database. After creating the new tree, just do the CTRL-A or drag & drop thing to get the games from the updated database into the new, blank tree.

I've hit you with a lot of information in this column over the last few weeks. So before we proceed with our sample correspondence game, we'll have a "checklist" of the things we've covered so far (with some extra explanatory notes and recommendations) in the next ChessBase Workshop. Until then, have fun!

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© 2007, Steven A. Lopez. All rights reserved.