[smerriman]

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Is there a reason Gib didn't bid 4 diamonds here?

(From a recent daylong).

[lycier]

Hello :

Good topic, good hand. Even you only offer a part of your bidding sequences, it isn't difficult to me. I have known its following exact bidding sequences.

Now let's expect real experts to give us a satisfactory answer.

[1eyedjack]

I *suspect* that the answer is something like this:

South requires very little incentive to cue bid below game, to protect against North having a very strong hand for the 3S bid (as is possible per the explanation).

North on the other hand needs to have extras in order to get excited, and bids 4S to limit total values to a minimum 3S raise.

I am not commenting on whether this is sensible, but I have seen human pairings adopt a similar approach. And I am only guessing that this is the explanation (as opposed to an outright bug).

It may be interesting to reproduce this hand with GIBs and see what explanation is given for a forced 4D cue by North, to see if it comments on total values.

[1eyedjack]

Duplicate

[bgm]

For a human pair, you may agree some frivolous/serious 3NT at this position which help to differentiate opener strength; but per GIB description it show 16-22 TP already.

Some human pair will agree cue of own suit promise 2+ honors, and GIB seems not having this also.

On the other hand it is not easy to construct a hand off 3 top tricks (barring 2 top tricks and a (♦) ruff), so it is relative safe to push one more, at least you will not miss the small slam (or directly 4NT/blast if you want). To try for grand seems you need to know the ♣ singleton and the value of ♥J combine with the 4th ♥ in the dummy. Not that easy given this sequence.

[lycier]

I had played such similar hand in the past. However I'm glad to see it again, the programmers are improving Gibs, 3♠ is just a evidence. It should know Gib always jump bid to 4♠ after rebid-2♠ in the past.
Today I intend to imitate your hand, and wanna to return your original condition, welcome you to tell me my wrong.

- First, I would better say you would better jump bid 3♠ according to Gib CC, this is your own issue. See its normal bidding sequence.

Hand-1

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- Second, I will imitate your hand.
Hand-2

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Hand-3

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From the hand above, we can be easy to find a serious issue.
Why must Gib probe for slam ? Why? Why ignore the controls on some side suits?
Please see those explanations about TPs.
3♠ says " 18-22TPs".
4♠ says "14-17 TPs".
So Gibs should have reason to think they have 32-39TPs in total.
I think this is a real reason.

[Stephen Tu]

I like a splinter in clubs by North after 2s, which should describe the hand fairly precisely.

As for cue bidding in other situations, if one hand has shown extras, the other hand should mandatory cue without extras if below game IMO. The first cue should show extras perhaps. Serious/non-serious (3 of trumps suit + 1 step) would be better but probably too complicated for GIB and too advanced for the average BBO player.

[smerriman]

Thanks for the replies.

bgm, on 2016-May-25, 04:39, said:

On the other hand it is not easy to construct a hand off 3 top tricks (barring 2 top tricks and a (♦) ruff), so it is relative safe to push one more, at least you will not miss the small slam (or directly 4NT/blast if you want).

How would you push one more - 4NT seemed the only option to me, and a response showing one ace won't help me decide whether to bid the small slam or not (seems likely to make with just the diamond ace).

lycier, on 2016-May-25, 06:38, said:

- First, I would better say you would better jump bid 3♠ according to Gib CC, this is your own issue. See its normal bidding sequence.

I considered this, but I saw no harm in bidding 2♠ either, especially when it was described by Gib as still wide ranging, as it allowed me more space for cue bidding. In fact, your third hand showed Gib makes the same decision to bid 2♠ rather than 3♠ after a 2♦ response.

[1eyedjack]

Interesting. So when would *GIB* rebid 3S? Any takers?

[lycier]

Stephen Tu, on 2016-May-25, 10:40, said:

I like a splinter in clubs by North after 2s, which should describe the hand fairly precisely.

As for cue bidding in other situations, if one hand has shown extras, the other hand should mandatory cue without extras if below game IMO. The first cue should show extras perhaps. Serious/non-serious (3 of trumps suit + 1 step) would be better but probably too complicated for GIB and too advanced for the average BBO player.

That's a good point.
Gibs have been only applied partly mini-splinter.

[lycier]

smerriman, on 2016-May-25, 19:27, said:

I considered this, but I saw no harm in bidding 2♠ either, especially when it was described by Gib as still wide ranging, as it allowed me more space for cue bidding. In fact, your third hand showed Gib makes the same decision to bid 2♠ rather than 3♠ after a 2♦ response.

Rebid-2♠ isn't really a correct description in such hand, usually shows limited hand without extra values, but jump 3♠ shows strong rebiddable ♠, we should say 3♠ is a perfect systemic bid with extra values, slammish bidding, that's to say only 3♠ - only one bid can tell opener's story, 2♠ never.

[1eyedjack]

lycier, on 2016-May-25, 21:38, said:

Rebid-2♠ isn't really a correct description in such hand, usually shows limited hand without extra values, but jump 3♠ shows strong rebiddable ♠, we should say 3♠ is a perfect systemic bid with extra values, slammish bidding, that's to say only 3♠ - only one bid can tell opener's story, 2♠ never.

And yet when you gave that hand to GIB, GIB rebid 2S. It may not be your choice of rebid, but at least GIB is bidding consistent with the explanation attached. Hence my earlier question that remains unanswered: On what hand would GIB rebid 3S?

[smerriman]

Putting the splinter aside for a moment, what is the ideal bidding sequence here from South's perspective?

If you think 3♠ is the best bid, what do you then bid after hearing a 4♠ response?

If you bid 4NT and hear 5♦, you can't do anything but bid 5♠ and you miss slam if North has the diamond ace.
If you bid 5♣ and hear 5♦, you have no way to continue investigating a grand slam; you're forced to sign off with 6♠.

Now suppose I bid 2♠ instead, which I think is better (and Gib agrees with me).

After a 3♠ response, I then bid 4♣ and think Gib should cuebid any ace. If I hear 4♥, I bid 4♠. If I hear 4♦, I bid 4NT, and then 5NT if I hear two aces. It won't get me to a grand slam here, but would if partner held another king, which is better than above.

With South's hand, there therefore seems to be no upside whatsoever to bidding 3♠ - you know exactly what you want to find out from partner, and this will not allow you to do so.

What is the upside of 3♠ that I'm missing?

(PS - I am definitely no expert - not even close to advanced - only ever played online. But I'm good with logic, and I can't see a logical flaw with my argument.)

[1eyedjack]

smerriman, on 2016-May-25, 23:51, said:

If you think 3♠ is the best bid, what do you then bid after hearing a 4♠ response?

Bear in mind that I am not suggesting that 3S is the best bid. GIB certainly thinks that it is not. But it is not an unreasonable agreement for 3S to show this type of hand.

If you use 3S to show this hand type, which would set Spades as trump in a single-suited hand with slam interest, then you should respect 4S by North as discouraging and, having said it all with 3S, then pass.

North should cue bid 4D over 3S.

[Stephen Tu]

lycier, on 2016-May-25, 21:38, said:

Rebid-2♠ isn't really a correct description in such hand, usually shows limited hand without extra values

That's not actually true, playing 2/1. Rebidding 2s doesn't deny extra values at all, it only denies the ability to make a more specific descriptive call, which depends on partnership agreements. 2S often conceals considerable extra values when there isn't a better call. For example I doubt many good players are rebidding 3s on AJxxxx KQx Kx Ax

The requirements for bidding 3s vary depending on partnership. For some, one needs solid or solid just missing the ace, so it requires actually a better suit than this, holding the J in addition, AKQJxx, or 7 cds, AKQxxxx, or KQJTxx. Or maybe at least the T, AKQTxx. The idea is to assure partner holding a stiff that this is the right trump suit, and try to avoid getting to the wrong trump suit. E.g. opposite x Axx AKQTxx xxx you'd really want to be in 7d not 7s and for most 2/1 players you can't get there after 3s since 4d now becomes just a cue bid not looking for an alternative trump suit. (Jump rebid traditionally demands cue bids so smerriman's hypothetical 4s call shouldn't happen).

The argument against such high requirements for jumping is that such good suits don't come up that often, and on some auctions it can get awkward to show extra values later.

[lycier]

1eyedjack, on 2016-May-25, 22:59, said:

And yet when you gave that hand to GIB, GIB rebid 2S. It may not be your choice of rebid, but at least GIB is bidding consistent with the explanation attached. Hence my earlier question that remains unanswered: On what hand would GIB rebid 3S?

You are an observant guy, jump 3♠ is a Gib systemic bid. For the reason of rebid-2♠, I first take south seat to bid 2♠, then left, let Gib replace me.
On the Gib CC, after 2/1 responding, there are some different between rebid-2♠ and jump 3♠ for sure.

[lycier]

Stephen Tu, on 2016-May-26, 04:42, said:

That's not actually true, playing 2/1. Rebidding 2s doesn't deny extra values at all, it only denies the ability to make a more specific descriptive call, which depends on partnership agreements. 2S often conceals considerable extra values when there isn't a better call. For example I doubt many good players are rebidding 3s on AJxxxx KQx Kx Ax

The requirements for bidding 3s vary depending on partnership. For some, one needs solid or solid just missing the ace, so it requires actually a better suit than this, holding the J in addition, AKQJxx, or 7 cds, AKQxxxx, or KQJTxx. Or maybe at least the T, AKQTxx. The idea is to assure partner holding a stiff that this is the right trump suit, and try to avoid getting to the wrong trump suit. E.g. opposite x Axx AKQTxx xxx you'd really want to be in 7d not 7s and for most 2/1 players you can't get there after 3s since 4d now becomes just a cue bid not looking for an alternative trump suit. (Jump rebid traditionally demands cue bids so smerriman's hypothetical 4s call shouldn't happen).

The argument against such high requirements for jumping is that such good suits don't come up that often, and on some auctions it can get awkward to show extra values later.

Yes, I see.
Anyway，as long as opener can make jump 3♠, it will show decent 6-card plus trumph suit with extra values in a goood hand, so it also is slammish, and usually request to probe for slam.
Rebid-2♠ should include some mini hand, even with 5-4 destributions, many USA experts very like it, I hate such style in fact.

[iandayre]

To go back to the original question, I would say that, first and most importantly, GIB is minimum for its 2/1 GF response. I am not suggesting that this is the best way to bid, but it is how GIB bids. Secondly, while 2S does not deny significant extras, it would seem to deny both significant extras and a very good S suit. 2S didn't promise 6.