🚀 go-pugleaf

Collins Williams (wmsc@aursx7.aur.alcatel.com) wrote:
: Hello all,

:   I would like to understand how to mess with
: gnu chess's opeing book.  As I undestand the makefile.  Existing book
: is run through gnuchessr and the gnuchess.data file is produced.

:   What information is stored in this file?  How does gnuchess decide
: wether to stay in book or to strike out on its own.  Can it ever stumble
: back into book?  What kinds of lines can or should I add to the book
: at by site to experiment with improving it?

If you look at book.c, you can see a structure called bookentry which
describes what is stored in gnuchess.data.  Basically, these are the
hashkey and hashboard for a position, a possible move, a hint (which
is a reply to the move), a count of how many times this position has
been seen in the book and a flag.

There is a variable called BOOKFAIL in gnuchess.h (currently set to 8)
which controls if gnuchess will ever refer to the book.  Once the program
leaves the book, if for the next 8 tries it can't find any move from
the book, gnuchess decides that the book is no longer useful and will
not refer to it anymore.  This mean that yes, the program can stumble
back into the book even if it leaves it.

As for what kinds of lines you want to add to the book, I think anything
goes.  Note that you can add poor moves in the book by indicating them with
a ?  (e.g. Ng5?).  Gnuchess will recognize the ? and the program will 
never play this move.

Kong Sian