The main advantage is the time used: the "naked" engine spent about 30% of the total thinking time in the opening, while the first engine was still in the Cerebellum book.
Having 1.4 time advantage factor ( 100%/(100%-30%) ), means about 0.5 doublings in time. So, if a book has an added value compared to just saving time in the opening, it should perform better than 0.5 doublings advantage, if not, equal or less.
I played games at two time controls on one thread:
First time control:
STC
Code: Select all
15''+ 0.15''
Score of BrainFish_Book vs BrainFish: 295 - 55 - 650 [0.620]
Elo difference: 85.04 +/- 12.34
1000 of 1000 games finished.
Second time control:
LTC
Code: Select all
3600''+ 36'' (1 hour + 36 seconds increment)
Score of BrainFish_Book vs BrainFish: 5 - 3 - 92 [0.510]
Elo difference: 6.95 +/- 19.21
100 of 100 games finished.
http://s000.tinyupload.com/?file_id=037 ... 8209928033
The doubling at this long time control is about 50 Elo points. The book advantage given by time saved while in the book should be again about 0.5 doublings, but it is almost beyond error margins that this is not achieved in LTC, never mind earlier STC 0.65 doublings result. In fact the result here is about 0.15 doublings (7 Elo points / 50 Elo points). The only explanation would be that the exit from the book is not very favorable compared to "naked" no-book engine at LTC (it seems favorable at STC). And the only real advantage is the time saved. Also, all the measures like Elo, Normalized Elo and Wilo show dramatically decreasing performance of the book with long time control.
It should be noted that Cerebellum is a "computer" Stockfish-analyzed book, maybe hand-tuned books using different criteria (say databases) behave a bit differently.