POWERBOOK 2005 on DVD
The Fritz Powerbook 2005 is an openings book and database that will run with Fritz or any Fritz compatible engine (Shredder, Junior, Tiger, Nimzo, etc.). You can also use it in ChessBase 7, 8 or 9 to conduct openings training and hone your repertoire.

The Fritz Powerbook 2005 contains 20 million openings positions, which were derived from 1 Million high-class tournament games. Together with each position all relevant information is stored: all moves that were played in the position, by players of what average rating, with what success and performance results. The games from which the Fritz Powerbook 2005 was derived are also included on the CD. This means that in any position of the opening tree, you can load and replay the games in which the position occurred.

The Fritz Powerbook 2005 represents the state of the art of current opening theory. It can be used to discover exciting new lines (e.g. never before played transpositions) and practice them against Fritz.

In the initial phase of a game, the program plays out of an “openings book”. This can consist of millions of openings positions, and for each of these, the program has full information on which moves were played, how often and with what results. The program stores its own experience with openings variations it has played. It learns from success and defeat.

The openings book is called the “tree” as the branching variations in the opening resemble the structure of a tree. The files that make up a tree are pretty large. The program requires about 80 bytes to store a position and all the information associated with it. You can leave the files on the program CD. However, in this case, the program will not be able to modify the book as it plays games (i.e., it cannot learn). Thus, it is advisable to copy them to your hard disk.

Some things to note:

• The size of the openings tree is limited only by the amount of disk space available. It is important to note that access to the information is always extremely fast, even if the files are truly gigantic.
• Existing openings trees can be easily extended, simply by importing games. This means that whenever a series of high quality games are available, the program can read them and extend its openings knowledge.
• The tree recognises all transpositions, even those that did not occur in the games from which the tree was generated. Sometimes you may be able to switch from one known position to another with a move that has never yet been played.
• The tree can handle reversed colours perfectly. For instance after 1.d3 d5 2.d4, the program is likely to reply 2...c5! and play the entire Queen’s Gambit as Black.
• The openings tree is not just an instrument to make the program strong, it is also a very powerful training tool for chess players. For this reason each move can be marked with chess symbols like “!” and “+=“.

Using the book window

In Fritz and ChessBase you consult the openings book by clicking on the “Openings book” tab at the top of the notation window.

This is what you see in the openings book tree:

• <Moves: (below tree icon) Sometimes a move will appear in grey, which means that it was never played, but leads to a position that results from some other line.
• Number of games: (N) The header displays the total number of games which led to the current board position. The N column displays the number of games in which each move was executed.
• %: Percentage score achieved by the move, always from the point of view of the colour to play. If the number of games is low, the percentage is given in grey because it does not have great statistical significance.
• Av: Elo average of the players of the move. If only a small percentage of the players had a rating, then the number is given in grey.
• Perf : Elo performance of the move. This is the rating a player would have achieved in a fictitious tournament, playing the move in all his games.
• Weights:The weights allocated to each move control the probability with which it will choose the move in a game. The value can range between –125 To +125. The values are initially set to zero, but may change when the program actually plays games in the individual variations. You could say that the program is learning from experience. The weights can be manually modified by right-clicking a move and selecting “Change weight”. If you reset all weights the program will use only the purely statistical information to select its moves.
• Prob and [%]:The first value is the purely statistical probability of the move, based on the number of times it was played and the results achieved in the games that went into the book. This is the probability of the move being played by the program as long as the weights have not been changed – either manually or by automatic learning. The value on the right [%] is the practical probability of the program playing the move. This is a product of the statistical evaluation and the weights. If you change the latter you can see how the [%] value (but not the “Prob”) changes. In Book options you can determine how much the weights influence the probability of play.

Display options

Right-click the book window to configure the display, i.e. enable or disable a number of elements of the tree window. These are the most interesting:

• Unplayed transpositions are moves that were not actually played in the games, which were merged into the tree, but which lead to another known position. This is a treasure trove for interesting moves which can come as a nasty surprise for your next opponent.
• Retro movesare the moves leading to this position from other positions in the trees.
• Statistics displays exact details for each move as a bar graphic at the bottom of the screen (as in the picture above). It shows in how many games the move occurred and what percentage of these games were won, drawn or lost. The graphics make it easy to take in the information at a glance.

Unplayed transpositions, retro moves The moves in grey (8...h6 and 8...Nc6) have never been played in the current position, but lead to positions that are part of openings theory. 8.0-0 and 8.Bd3-e2 are moves that lead to the current position.

How to navigate the tree

• Use the up/down cursor keys to move the headlight bar up and down.
• Use the right/left keys to move forward and backwards in the variations.
• Click a move with the mouse to move forwards in a variation.
• Right-click a move to annotate it.
• In the same menu you can exclude a move from tournament games. The move appears in red. Repeat the action to make it playable again.

	Right-click the book window to execute a number of commands, e.g.: retrieve the game in which the curren position occurred; sort the moves prune or delete the tree etc.
	Right-click a move to annotate it (with !, ?, +–, etc.); make it the main move in the current position; instruct Fritz never to play this in tournament mode; modifiy the weighting manually; delete the move or variation

Installing Powerbook 2004

In Fritz you click Edit – Openings book – Copy tree to hard disk. This will copy an openings tree from the CD to your hard disk, making access faster. Doing this also allows the program to learn from the games it has played and by reading databases.

Importing games to the openings book

Click Edit – Openings book – Import games. This very powerful function allows you to extend the openings book very quickly and with no technical hassle. You can, for instance, import all the games of the latest ChessBase Magazine, or only those from the lines you play. The games will be merged to a tree of positions. The length of the variations ist limited in two different ways: You can specify that every variation should be “n” moves long; or, more sensiblly, you can limit the variations relative to the ECO classification. This results in long variations for theoretical main lines (ECO classification position found late in the game) and short variations for side lines (i.e., early deviations).