[hanp]

In various different auctions GIB goes wrong when I show a second suit. For example, if I open 1D, the auction becomes competitive and on the next round I bid 4C, GIB will think I have rebiddable (sometimes twice rebiddable?) clubs, and 3+ diamonds. GIB will then not correct to diamonds even with longer diamonds.

It seems to me that this is a fundamental problem that should be fixable.

[barmar]

Yeah, the explanations sometimes seem like GIB thinks we open 1D with 4=5 minors. But first of all, I don't think I've ever seen it do that (there was a bug fixed a while ago where it occasionally opened a short minor). And second, you only have to do that with minimum hands; if the hand is strong enough to come back in at a high level, it should be strong enough to reverse.

[arigreen]

I've seen a couple of these reported recently. For example: 1D-(1H)-P-(2H)-3C was explained as showing "twice-rebiddable clubs". Twice-rebiddable means a decent six card suit, so all the other GIB's at the table thought this GIB had 6 clubs, and, by inference, 6 diamonds as well. I fixed one of the broken rules, but there may be others as well that need to be fixed.

[barmar]

Take a look at this one from yesterday:

Scoring: MP

2♣-2♦
2♠-3♦
3♥-4♣
4♥-4♠
4NT-6♠

---

6♠ was explained as "4+ C; 4+ D; 3+ S, 10+ total points". The lead was a trump, and I had to guess whether to take a club hook, run the ♦Q, or take a diamond ruffing finesse, and spades had to be 3-3. I guessed right and they were, so I shared 98% of the matchpoints (helping me get 71% for the tourney, I think a personal best of my entire bridge career).

I think my 4NT was explained as "Invitational to 6NT; 23+ points" (why doesn't the bridge movie preserve the explanations of the human's calls?). I don't think it was an overbid, since at least one of my minor queens is likely to be working.

[jdonn]

I have noticed when I transfer to spades then bid 3♥ the explanation is correct as 5-5 GF but partner goes back to spades even with shorter spades. And if I then bid 4♥ he bids 4♠. And if I then bid 6♥ he bids 6♠...

As far as auctions starting 2♣ p 2♦ p, 2M p 3♦ be careful. He plays a second round 3♣ bid as a second negative and therefore often makes the 3♦ bid on hands with short (4 or maybe even fewer) diamonds and 5+ clubs.

[barmar]

Good point, Josh. How hard would it be to change GIB to use either control step responses or 2♥ as an immediate negative? How many decent bridge players still use cheapest minor as the 2nd negative?

[jdonn]

Actually I'm fine with 3♣ second negative but in that case I wish gib would either rebid 2NT more often, or just play 3♦ waiting instead of pretending it shows diamonds. Even not having a second negative is fine with me, or using 2NT for it. There are lots of possible fixes, anything but the status quo!