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Opening Book

367 bytes added, 15:28, 7 July 2019
Rewrite first 2 options
* All positions
Some [[Databases|databases]] use a list of common opening lines (The first two options are probably easier to implement. They are usually stored in PGN as text files), while others hold a list such as files of PGN format (for openings lines) or EDP format (for last positions (usually stored in EDP files) that arise in common openings. The first two options most advantage is that by using text form they are probably easier to implement readable, understandable and understand editable by human. However, while the third has main disadvantage is that they may take too much space as well as time for searching. If we store openings "continuously" (all possible opening positions) both data size and searching time become too huge. In practice, those opening books are usually very small with some important advantages, especially lines or positions only. They cannot be used for real game playing but for computer chess enginestesting.
The third has some important advantages, especially for computer chess engines. Opening databases built on all positions are usually more space efficient and overcome the problem of [[Transposition|transpositions]]. Often these positions are stored as hash value to allow fast access. Some opening database formats store with each position as well some information about it. (e.g. number of times occurred, number of games won by white/black / drawn with this position, average/maximum Elo of players playing to this opening position, chess program's success with the position). So when a chess program has to decide on a move, it will look up all positions that could arise after moving in the database and then make a decision upon the information given with each position.
=Generation=

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