Flattening an opening book

An opening book created from a PGN file will contain many lines which will never be played by Amy since they occur only once in the book. You can remove these lines by flattening the book. This process removes all entries which occur less frequently than some threshold.

Example 3.2. Flattening an opening book

White(1): flatten 5
Flattening book with threshold 5
Read 183189 entries, wrote 5272 entries

The flatten command produces a file Book2.db. This file can be used instead of the standard opening book Book.db.