[Stephen Tu]

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I think NMF after 18-19 2nt rebids has to be cleaned up some.
How to find 4-4 fit in the other major when 5-4. Also an issue when North is 4-5 in the majors, opener can be 4-3 in majors, how to find fit?
There are two stds for opener to follow; one is give priority to other major, the other is give priority to hearts. Which one is GIB doing?

On this auction, 3h says 4h 2s, which to me is wrong, it should be 4h, 3- spades.
And 3nt is weird, saying 5-h, 5-6 spades; it should be 3-h, 5 spades IMO.

[aguahombre]

First priority might be to clean up the use of NMF....responder bidding hearts with hearts to get that possibility out of the mix if he bids 3D.

[Stephen Tu]

There are many people who play that direct 3h bid on auction 1c-1s-2nt-3h shows FIVE hearts. Otherwise you have a difficult problem holding 5-5 in majors if auction goes say 1c-1s-2nt-3h-3nt-? if partner is sometimes rebidding 2nt with 2245/2326/2236 type hands.

So normal to bid nmf with 5-4 in majors, IMO.

[Bbradley62]

Stephen Tu, on 2012-May-01, 19:38, said:

There are two stds for opener to follow; one is give priority to other major, the other is give priority to hearts. Which one is GIB doing?

On this auction, 3h says 4h 2s, which to me is wrong, it should be 4h, 3- spades.

I believe that Barmar has told us that first priority is to show 3-card support of responder's major. I will look for the reference.

Stephen Tu, on 2012-May-01, 19:38, said:

And 3nt is weird, saying 5-h, 5-6 spades; it should be 3-h, 5 spades IMO.

This oddity exists for many NT bids in GIB's system.

[Stephen Tu]

Bbradley62, on 2012-May-01, 21:30, said:

I believe that Barmar has told us that first priority is to show 3-card support of responder's major. I will look for the reference.

This should be changed then. It's going to be nigh impossible to find a 4-4 heart fit if opener is going to bid 3s first. 4h by responder should be slam try after that.

[aguahombre]

Stephen Tu, on 2012-May-01, 21:42, said:

This should be changed then. It's going to be nigh impossible to find a 4-4 heart fit if opener is going to bid 3s first. 4h by responder should be slam try after that.

So, settle for the 5-3

[Stephen Tu]

aguahombre, on 2012-May-01, 21:55, said:

So, settle for the 5-3

But the 4-4 is reasonably often worth an extra trick, this could be crucial for game or slam. There's no reason GIB should play inferior methods.

[barmar]

There are many different styles for this. Some say the first priority is to show 3-card support of responder's suit. Some say to bid the cheapest. I personally prefer to show 4 of the other major, even if it requires bypassing responder's suit (e.g. if I have 4=3=x=y and the auction started 1m-1♥-(1/2)NT), because of the extra trick that often comes from being in the 4-4 fit. But I know I've played with many players if my playing level who prefer the first or second approaches.

I think the most common I've encountered is "cheapest". I'm not sure what expert concensus is; it's probably complicated by the existence of other conventions like Wolff Signoff. But I'm not going to unilaterally dictate my preference.

If you think this is really important, I'll ask Fred -- he's our expert system arbiter. But since he's busy with the Trials this week, I don't expect an answer from him for a while.

[Stephen Tu]

With good players, I've played "other major" first, and I've played "hearts" first. But I can't remember anyone playing spades first when responder has spades, like GIB wants, at the 3 level.

Now after GF checkback on the *2 level*, I've played responder's major first, but there's considerably more room to work things out then. Also 2 level is different since GIB doesn't bypass 1s to rebid 1nt. Auctions aren't necessarily treated identically.

I do want GIB to be able to bid 4h here. Rebidding 3nt is bizarre, whether or not 3h denied 3 sp (and I strongly feel that 3h should not deny 3s, and that "other major" first or "hearts first" are acceptable and a lot more common than "support major first, other major denies").

[barmar]

4♥ is the book bid here. In my tests, in MP mode it bids 4♥ on 10 out of 11 simulations, 5♥ on the 11th. In IMP scoring, it bid 4♥ on 9 out of 10, 5♥ on the 10th. The only time I got a 3NT bid was in total point scoring.

[barmar]

I looked at the hands it dealt in the simulations that resulted in the 3NT bid.

First, the auction has told it that your shape is exactly 2=4=3=4, because of the rule that 3♥ denies ♠ support, and because you didn't reverse (which would show 5+♣). The worst club suit it dealt to you was K852, and most were significantly better.

In most of the hands in the sim, 3NT and 4♥ both made, and 4♥ usually played a trick better, sometimes 2 tricks. But there was one hand where 3NT makes, but 4H goes down because the opponents get a ruff. On the other hands, being in H gains an average of about 20 points, but the one hand where it cost 730 totally cancelled out all these small gains (there were 13 hands in the simulation). There were no hands in the simulation where 3NT went down.

[barmar]

I asked Fred, this is what he had to say:

Quote

My sense is that this is not important enough to fix/change provided that GIB will always find a 5-3 or 4-4 fit if either of these exist. If both exist, then it is not that big a deal which one GIB plays in as far as I am concerned.

The preference for 4-4 versus 5-3 that is a common theme in bridge literature tends to manifest itself most often at the 6 and 7 levels. At the game level it tends to be far less important (and the 5-3 fit will sometimes be the winner for various reasons, notably in terms of guarding against a forcing defense).

I don't have any strong feelings in terms of what response scheme to NMF is "best" from a pure bridge point of view. As I recall, my original reasoning for suggesting "show support first" was that I thought it would tend to result in simple auctions for our users.

The only change he did suggest was that we should disable simulations from overriding the rules that say to play in the 8-card major fit.

[Stephen Tu]

Yes, it makes difference more often at slam level.

My arguments would be:
- if you don't find the 4-4 fit now, how the hell are you going to find it when you do need it for the slam level? Slam isn't horribly uncommon when one of the partners has 18-19.
- the show other major first and show hearts first schemes are simply way more commonly played out in the world than "show support first", in my experience. It's what people are used to. Given that GIB is playing NMF at all (it could just play natural), I think everyone playing checkback schemes are far more used to those than "show support first", and don't find it particularly complicated. If human decides to show support first if GIB switched to another style, you get to playable contract still. If GIB shows other major first, then supports human later, human will understand the auction and know that 4M is to play with 3M support.

- even if GIB wants to conceal its other major, it ought to be able to grok the auction 1c-1s-2nt-3d-3h-3nt-4s, and not assume that it is 2sp-4h. I'd be able to survive this auction with pickup partner no discussion.