[steve2005]

if you are not going to repeat the finesse it makes sense to play Ace and another trump to
avoid a ♦ ruff

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thank pilowsky for diagram

[smerriman]

The diagram shows you in South. Are you GIB

OK, I assume you were disconnected, and a basic GIB took over. GIB doesn't make assumptions about what a play does or doesn't show; finessing is the best at trick one, but on the next trick it considers East ducking from Kx just as likely as anything else.

Matt Ginsberg's original paper specified that it should calculate conditional probabilities of whether opponents have certain cards based on whether a certain play earlier on would have been an error, to handle situations like this. But apparently it made the program way too slow, and it was taken out (on reflection, not too surprisingly; if GIB often struggles to deal any hands that match a bidding sequence, and believes you way too much when you do something a tiny bit unusual, imagine if you restrict it further by removing a whole heap every time someone plays a non-optimal card..)