[Jyrki_63]

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Slam choice

After my 4H bid I think that I had bid promised 5+ hearts and longer clubs since I opened clubs and bid and rebid hearts. It was not clear to me which suit was meant to be trumps, but as GIB later asked for the queen it must have been hearts, so my 6C response showed HQ and CK. Given this, what kind of a simulation propelled GIB to think that (opposite its singleton hearts and AQT clubs) hearts would make a better trump suit? Did I manage to mislead it with an earlier bid?

We shall never know, whether I would have managed 6C. Others went down due to the bad heart split, but if you take exactly two high hearts before ruffing one, there is time to recover: ruff two hearts and take advantage of the 22-club split.

[calm01]

My experience is that GIB cannot usually effectively cope with partner offering 2 suits to select from. Even at the 2-level GIB can sometimes prefer a known 5+/1 major fit to a 3+/5 card minor fit.

In this example your 4H bid is reasonably described as 6+ C and twice rebiddable H. Often GIB appears to ignore such length information in its preference decisions.

I get round this common employment of selection blinkers by GIB by bidding any 5 card major first even when minor is a good 6 carder - it seems to cause less damage in the long run. GIB bids reasonably or well in reply to a single suited partner so it usually seems to pay to decide which single suit you will express to GIB and suppress any second suit which just seems to confuse.

[Antrax]

The alert to 4♥ shows some conflict between rules: it says you have 6+ C, but later says you have 3 (and later bids show 3-). More important, you show that your hearts are "twice rebiddable" which I think is a good six-card suit or better.
I think the alert on 6♣ is also interesting - your answer shows the Q of clubs, but GIB is holding it. A human would rethink here, but obviously GIB can't

[Jyrki_63]

Antrax, on 2012-January-22, 01:19, said:

The alert to 4♥ shows some conflict between rules: it says you have 6+ C, but later says you have 3 (and later bids show 3-). More important, you show that your hearts are "twice rebiddable" which I think is a good six-card suit or better.
I think the alert on 6♣ is also interesting - your answer shows the Q of clubs, but GIB is holding it. A human would rethink here, but obviously GIB can't

Even if my bidding had promised a 6-card heart suit (I don't think I did, but it is not entirely clear to me what is GIB's definition of a "twice rebiddable" suit), then I should still have longer clubs, and GIB should place me with -, AKQxxx, -, Kxxxxxx, and its preference is still incomprehensible. Furthermore, GIB could blame me that 7C was not on :-)

If this is too difficult to code, may be it would be easier for GIB to bid according to a 4-card major opening system, where there are no systemic exceptions to the rule that the first bid suit is the longest?

Does GIB not maintain a list of possible patterns compatible with my bidding? There are only 560 possible patterns, so the list would not be very long for a computer program?

[barmar]

The explanation of "twice rebiddable" is in the sticky post about understanding GIB explanations.

GIB never said 3- C. 3-card C means at least 3. "3-card" is a suit quality description, it's the same type of feature as biddable, rebiddable, etc. This just means that none of the later bids specified that the clubs were of a higher quality than initially shown by the opening bid, the way they did about the hearts. GIB doesn't automatically update suit quality descriptions when it gets information about length (this is something I might try to change some day).

The book bid over 4♥ is 5♣, but simulations told it to bid Blackwood instead. For some reason, the hands it was dealing you were 6-6 in the round suits. I'm investigating this.

[barmar]

I see what's going on. A twice-rebiddable suit is 6 cards with at least 3 out of 5 honors, or any 7-card suit. So since 4♥ showed 6+ C and twice-rebiddable H, you had to be 6-6. And since it thinks you have at most 4 points in ♣, and only one other card outside hearts, they have to be very good, so it thinks they'll play well opposite a singleton. And since you only have one card outside your two suits, you don't need to ruff anything in dummy.

Here's a typical hand it's dealing you:

---

[Bbradley62]

barmar, on 2012-January-23, 15:19, said:

GIB never said 3- C. 3-card C means at least 3.

According to your "Understanding GIB Bid Descriptions" document:
Suit Quality
3-card
exactly 3 cards

[barmar]

Bbradley62, on 2012-January-23, 17:28, said:

According to your "Understanding GIB Bid Descriptions" document:
Suit Quality
3-card
exactly 3 cards

Sorry, I copied the descriptions from a document that describes how GIB calculates suit quality. So when it's looking at a suit and assessing its quality, it assigns "3-card" if it's exactly 3 cards.

When you're reading the descriptions, consider these all to be minimums. They're what a bid has promised, but the suit could always be better. E.g. when you open 1♣, you're showing a 3-card suit, but of course it could actually be better. And if no later bid specifies that the suit quality is better, this will be carried forward into future descriptions. A bid that shows extra length, but doesn't explicitly mention quality, will not update this, so you end up with the seemingly nonsensical "6+ C, 3-card C". It's because these are two independent attributes, and many bidding rules only specify one or the other (it's similar to the relationship between HCP and TP).

As I said, one of these days I'd like to make GIB automatically reconcile related attributes like these, to prevent this nonsense.

[Antrax]

barmar: the alert for 4♥ says "3-card ♣". Then the alert for 5♣ says 3- ♣ in the end, for some reason. So you have 6+♣, a three-card ♣ suit but it has 3 or less cards. Then the alert for 6♣ shows K+Q♣, when GIB is holding the ♣Q. Do you have some priority mechanism for settling conflicting rules that you can document, so players will know what GIB really expects of their hand when the alert is confusing?

[Jyrki_63]

barmar, on 2012-January-23, 15:32, said:

I see what's going on. A twice-rebiddable suit is 6 cards with at least 3 out of 5 honors, or any 7-card suit. So since 4♥ showed 6+ C and twice-rebiddable H, you had to be 6-6. And since it thinks you have at most 4 points in ♣, and only one other card outside hearts, they have to be very good, so it thinks they'll play well opposite a singleton. And since you only have one card outside your two suits, you don't need to ruff anything in dummy.

Here's a typical hand it's dealing you:

---

Barmar, thank you very much for looking into this. Duly appreciated. I have trouble accepting that my 4H bid was wrong, but so it seems.

A few questions remain:

1) How was I supposed to show a heart suit that is rebiddable but not twice rebiddable? My 3H only showed a suit like KJxx (alert says 4+ hearts) in a hand that didn't want to reopen with a double. If I rebid hearts, then I'm suddenly showing AKQxxx or better! How do I check for 3-card support? I guess a direct 4H shows 5, and a case could be made for that bid, but this hand has too many losers vs. a yarborough for the bid to appeal to me. Remember that the opposing 2S bid tells that at least one of my suits is not breaking.

2) I surely cannot hold that moose! A) that hand is either a 2C or a 1H opening, not a 1C-opening, B) my reply to RKCB would have been 3+ void (6D IIRC), C) Wouldn't GIB want to be in 7C opposite that hand?

@Antrax, I'm fairly sure that GIB intended hearts to be the keycard suit, so my 6C showed HQ and KC.

[barmar]

Antrax, on 2012-January-24, 01:06, said:

barmar: the alert for 4♥ says "3-card ♣". Then the alert for 5♣ says 3- ♣ in the end, for some reason.

It doesn't say "3- C", it says "3- controls", but it's getting cut off.

Quote

Then the alert for 6♣ shows K+Q♣, when GIB is holding the ♣Q

Do you mean where it says "Queen & King"? Since you're in an RKC auction with Hearts as trumps, responding to the 5♦ Queen ask, 6♣ shows {HE}Q+♣K.

In any case, when describing the responses to Blackwood, it doesn't matter what North has. If South misbids, his bids still "show" the things North knows he can't have.

[mgoetze]

The heart of the problem is the description of 3♥. Of course two humans playing with each other would double if they really had a hand with just 3-4 clubs and 4 hearts, so for them 3♥ shows ♣>♥. But when playing with GIB doubling is very dangerous as GIB is likely to leave it in. GIB assumes it is playing with itself and thus prefers to introduce 4-card suits at the 3-level with absolutely no safety net, after all 2♠x+1 is pretty embarrassing.