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Does GIB Understand Lebensohl?

#1 User is offline   awm 

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Posted 2014-October-08, 00:03



I'm not sure what GIB north is doing here. Besides the somewhat strange action of bidding the minor before the major in response to a takeout double with equal length, GIB is also substantially underbidding his hand.
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#2 User is offline   1eyedjack 

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Posted 2014-October-08, 00:22

In another related thread, someone mentioned that GIB's version of Lebensohl treats an immediate 3/2 suit in response to the double as forcing, so it goes through 2N on a very wide range.

Unplayable. Non-standard. (and not verified by me).

But again the avoidance of the major suit is also a repeating issue.

Quite aside from which, the explanation of the 3D bid shows 9- total points. Which is actually quite reasonable. Except that he has 11 total points.
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#3 User is offline   Bbradley62 

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Posted 2014-October-08, 10:53

View Postawm, on 2014-October-08, 00:03, said:

I'm not sure what GIB north is doing here. Besides the somewhat strange action of bidding the minor before the major in response to a takeout double with equal length, GIB is also substantially underbidding his hand.

At least GIB is consistent: http://www.bridgebas...rted-lebensohl/
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#4 User is offline   uva72uva72 

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Posted 2014-October-08, 11:39

As pointed out by Stephen Tu in a related thread, North should bid 2NT followed by 3 with its hand to show invitational values with exactly 4 cards in the suit (a jump to 3 directly would show the same values with 5+ cards).

This hand is a sort of robot tri-fecta, bringing together issues related to:

faulty implementation of lebensohl (direct bid of 3 of lower ranking suit should be constructive, not forcing, and 2NT following by pass or 3 of lower ranking should be 0-7/8)
suppression of major suits in favor of minor suits in response to take-out doubles
not infrequent suppression of spade suits longer than 3 cards in competitive auctions
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#5 User is offline   uva72uva72 

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Posted 2014-October-10, 12:31

My link

This is an interesting companion piece. Note that this hand is weaker than that in the original posting, yet the robot has taken what accepted practice (and the system notes) say is the stronger action (hence my ill-fated move over 3, thinking that North would surely have the advertised 10-12 total points). It is, though, actually just a little weaker than what I would in high cards from a live partner. So, is this hand an aberration or is the original hand the outlier?

And why, with two suits of equal rank and length, does the robot always seem to bid the worse of the two? I'm not sure that I would have passed 3, but I would have thought about it longer looking at 10xx than at AKx. It's tough to draw accurate inferences and apply judgment when your partner bypasses AKxx to bid xxxx. It shouldn't be about preparing a rebid, because North is not all that likely to need one; and meanwhile partner is misjudging the hand.
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#6 User is offline   Stephen Tu 

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Posted 2014-October-10, 13:03

Weird that it shows 10-12 when having only 8 hcp + 1 for the doubleton. Personally I think it's a bit light since the SJ is dubious, but GIB doesn't devalue points in opp's suits as it ought to. But given that it is not treating the hand as weak, it's perfectly reasonable to bid the higher ranking of two equal length suits, regardless of suit quality, when not strong enough to make some cue bid to try to force doubler to reveal a real fit (cue is best at finding 4-4 fit reliably, but it forces up a level). This is because if doubler bids again anyway, as you did, it can now show the second suit, and still let you back to the first suit at the same level. For example say you had a strong hand with a 4cd diamond fit, you cue looking for the spade stopper, can't find it, but now can at least get back to 4. If on the other hand it had bid clubs when you had clubs, and you cued, to show the diamond suit it would have to then bid 4, and if you wanted to get back to clubs you'd be at the 5 level. If you had diamonds, and to avoid reversing it just rebid clubs again, the diamond suit would be lost. Bidding the suits in this order lets you get to either fit if it exists at the 4 level if doubler bids again.

This is a general principle many weaker players don't pick up, they are used to bidding 4 cd suits up the line as responder (which works because opening the bidding, opener will bid up the line), whereas in response to double they should bid the higher first (because doubler *won't* bid up the line, will pass/cue) so they can bid the lower later if given the opportunity.
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