Author: William Penn
Date: 17:54:45 12/28/04
Statistics errors in opening books created with Shredder8/Fritz-GUI ------------------------------------------------------------------- I have been creating opening books for quite awhile with the Shredder 8 CB/Fritz-GUI. [I'm talking about the same GUI that comes with Fritz 8, Junior 8, etc. - not the "Classic" Shredder GUI. Too bad such ambiguities exist, but hopefully that is clear enough.] The procedure (from the chessboard window in the GUI) is: 1) File menu, New, Openings book... (creates a new opening book) 2) Edit menu, Openings Book, Import Games... (imports games from any desired database) The resulting opening book can be displayed in the Book Pane. That is available by default as one of the tabs in the Notation pane, along with the Notation and Scoresheet tabs. Or it can be displayed separately by selecting "Extra Book Pane" from the Window menu, Panes... For any given position on the chessboard, the opening book shows the number of games, percentage scored, average rating, performance, and probabilities - overall, and for each of the possible moves in the position from the database involved. A histogram (bar graph) can also be displayed at the bottom of the Book Pane with the number of white wins, draws, black wins, percentages, etc. Much to my dismay, I have just discovered that the data and statistics shown are inaccurate. There must be a bug somewhere. While the total number of games in a given position appears to be correct in all cases, the other statistics & data for the variations is incorrect. For example there may actually only be one (1) game in the database for a particular move from the position, but the Book Pane may say that there are 3 games, or 5 games, etc. with corresponding incorrect statistics. Search of the database involved for that position proves that the displayed statistics are incorrect, which is easy to do when only a few games are involved. This error always displays more games than actually exist in the database. Exactly where the "extra" games come from is a mystery, because they do not exist in the database. It could be some kind of tree-building error when the games are imported. Or it could be an error in how the data is displayed (more of a GUI-based error). I don't know which. I also don't know if the error relates to the Length designated when importing games. That dialog box which appears asks you to select an Absolute length or an ECO-relative length of 1-100. This determines how big the tree is. The larger the Length selected, then the bigger (more MB or GB) the resulting opening book. I usually choose a Length in the range of 15-35, depending on the size of the database. I also don't know if the error relates to the size of the database involved. Most of my databases are large, the largest over 3,000,000 games. Or perhaps there is some limit on the size of the resulting book files, but I don't know. At this point, I also don't know exactly how bad the error is. If it's only a handful of games, it wouldn't matter very much when the sample of games in a given position is large. The uncertainties involved makes the resulting statistics practically worthless, pending further research. Too bad, because it could be quite valuable if accurate based on the database involved. At this point, I'm not aware of any way to avoid this bug. Does anyone know how it can be avoided? My apology for saying "I don't know" so often, but alas there is no detailed documentation or instructions for these operations insofar as I'm aware. You just have to discover them on your own, then try to get lucky, I guess. Alas that is typical of Chessbase documentation. They assume you already know everything. WP
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