The file `gnubg.weights' contains the trained neural net weights for most of @gnubg{}'s position evaluators. Like `gnubg.bd', it should be kept in either the current directory or the installed directory.
A binary variant of the weights file named `gnubg.wd' can also be used (this version can be loaded more quickly, but is not portable between different computer architectures). It will automatically be built during the compilation process, and used in preference to `gnubg.weights' if found.
You should be able to obtain a copy of the weights from wherever you found the @gnubg{} distribution. If you wish to start @gnubg{} without any weights (and train your own), you can use the @option{--no-weights} option (see see section Invoking @gnubg).