BBO Discussion Forums: Nice unblock, too bad it didn't work - BBO Discussion Forums

At first I thought it was funny that both defenders played their club honours under mine to allow me to make two underserved overtricks. But presumably they played each other for ♣9. So well done GIB, this is the kind of play which human opps don't figure out, at least not at the local club in Hamilton East. Too bad it didn't work this time.

helene_t, on 2018-October-20, 04:37, said:

Do you happen to have the tournament number? I think I played that hand yesterday, but if not, GIB made the same play in the same suit.

I must be missing something. With a hand full of good spades, what reason does East have to unblock?

helene_t, on 2018-October-20, 04:37, said:

GIB frequently randomly unblocks or tosses winners/high cards. Usually it has no bridge reason and usually it costs a trick. There are no indicators that this wasn't just a random play of a high card.

wbartley, on 2018-October-20, 10:28, said:

If East plays low, declarer simply runs the ten and guarantees 10 tricks. Playing the Q is required to hold declarer to 9 tricks.
Switch the positions of the 8 and 9, and unblocking both the Q + J is required to beat the contract.

johnu, on 2018-October-20, 13:02, said:

GIB usually randomly throws away an honour when it figures it can't cost, and most of the time it is correct double dummy. Mistakes are usually in interpretation of the bidding, or when it makes it tougher for partner. Given it's the right play here and is easy for GIB to work out, there are no indicators at all it was done randomly.

johnu, on 2018-October-20, 13:02, said:

Clearly South should have continued hearts after the jack held to set up 9 tricks. Both East and West can see 1 spade trick, 2 hearts, 4 diamonds, and 2 clubs for 9 tricks with a heart continuation. Why would South play on clubs with ♣A854 where this sets up a club entry for East to cash spades if they hold ♣QJx, or ♣Q9x or ♣J9x, etc? Any analysis by GIB would be on double dummy lines.

johnu, on 2018-October-20, 14:05, said:

I don't understand what point you're trying to make.. South is a human?

You can see East throwing the queen is optimal with the current layout, as well as if South has A854. So there's no doubt East got it right.

From West's perspective, East can't have QJx, or J9x, because West holds the J, so I'm not sure what you meant by those cases. Are you saying that West should infer East can't hold the 9, because otherwise South would have led a heart? I don't see how that is true - South doesn't know the heart finesse is working regardless of whether they hold A954 or A854.

Yes, GIB defends on double dummy lines for future tricks. But it doesn't assume the declarer had double dummy knowledge for all previous tricks and rule out any layouts where the human didn't play the double dummy optimal line.. that would be ludicrous.

A human should throw the jack. GIB did too, and it wasn't by accident.

smerriman, on 2018-October-20, 17:45, said:

I guess my point is that if GIB makes unblocking plays 10 times and 9 of them are bad or hopeless plays that just give away tricks, should GIB get credit for the 10th time where unblocking may be the correct play? I favor the view that GIB is the blind squirrel who managed to find the nut until I see a lot more success stories.

Perhaps success stories aren't posted about I suspect you're experiencing confirmation bias, where you're only noticing hands when it did cost (and including some cases like this where it was still the right play). Would need to do a proper analysis of thousands of hands before making claims like that - I have a feeling 9/10 is just a teeny bit inaccurate.

Yes, I know there are cases where it costs.

And yeah, they should change how GIB selects between dummy double equals.

smerriman, on 2018-October-20, 13:32, said:

I think you mean to say that if South started with specifically A54 of clubs, the play of the Q is necessary to force an entry to East's hand (the eight of clubs). It's technically not an unblock. In fact, it's the opposite of an unblock.

Isn't that the definition of an unblock?

smerriman, on 2018-October-22, 13:21, said:

No. An unblock is to force an entry to a different hand and not via normal promotion of honors. Unblocking is when you jettison a card to keep from winning a trick with it.