Posted 2018-September-02, 12:48
GIB, first few tricks, is simulating *double dummy* play, meaning it can see whether or not the heart finesse is going to work. It is playing sample deals looking at ALL the cards. Therefore (barring rare void diamond which may not show up given its limited sample size of analyzed deals to maintain performance), the diamond ace is a free play (neither hurting nor helping), because if the heart hook is on it will take it while if it is off it will refuse it (or take the backwards finesse for that matter, if Txx/tx with west) and take the club hook. So from GIB's point of view playing diamond ace is equal to playing a top heart honor preparing for a finesse, and among equal plays it will randomly choose one or the other. It is not until the point of no return (heart hook) that it can realize that DA was a mistake, since earlier it was assuming it was infallible at future guessing, seeing all the cards. If you are infallible at guessing, and no diamond void, basically why not cash the DA since it makes no difference? There's no logic in there, looking at all the cards, for it to decide the DA is bad, because it takes an equal # of tricks on all the deals compared to alternative plays.
It takes the single dummy reasoning advanced engine, which realizes it has to play for cards in particular spots later, and might get some of these wrong, to avoid these kind of errors, but it isn't kicking in soon enough, which is what we have been discussing. Whether advances in computer speed/memory are enough for it to kick in earlier and maintain performance for the multitude of users, is something for BBO developers to measure.
It also doesn't have the human reasoning that the club hook is very likely on, very hard for west to duck trick 1.