Dr. David Kirkby wrote:

This suggests to me that the results of computer analysis of positions
get skewed if the ***same*** set of GM games are used both to create
an opening book in a chess analysis program AND as a reference
database in scid, chessbase or whatever.

Most of the programs I've seen may choose opening moves based on
frequency, but they don't typically use the book information in the
search (other than perhaps to order move - which would be a subtle form
of influence indeed).

So the analysis the computer returns is probably tactically sound unless
the database person has tried to get clever.

Currently GNU Chess has a fairly crude method for using it's book games,
which picks the best scoring moves, with a popularity cut off (b4 has an
excellent score but hasn't been played enough). This very crude
algorithmn occaisonally throws a wobbly, but against myself it often
leaves it with a winning advantage by the time it leaves booksigh.

Whilst GNU Chess now thinks (in it's opponents time only) in the
openings - this is purely to prevent it from reaching a middle game with
no analysis - which cost it a blitz game against a FIDE master where it
made a really bad blunder due to having such a complex position it was
unable to complete even a preliminary search of the position in time.

Contary to "folk wisdom" computers often do fairly well without an
opening book, and I'm tempted to go the complete opposite and just use
opening books as a source of move ordering information for the search
algorithmn. But I think the time penalty against players with carefully
prepared books may be too large.

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