[emalka]

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If S bids 4♥, GIB doubles, but if S makes takeout double, GIB bids 4♠
This must be a bug ?

[barmar]

Over a takeout double, 4♠ is preemptive, so it doesn't need a strong hand.

Over 4♥, GIB needs 13 total points to bid game -- you don't preempt over preempts. With 11-12, it doubles to show almost-GF values.

GIB was fooled because South has a strong hand, not the week hand that was expected. The freaky distribution allows both sides to make game.

[emalka]

barmar, on 2011-December-05, 16:23, said:

Over a takeout double, 4♠ is preemptive, so it doesn't need a strong hand.

Over 4♥, GIB needs 13 total points to bid game -- you don't preempt over preempts. With 11-12, it doubles to show almost-GF values.

GIB was fooled because South has a strong hand, not the week hand that was expected. The freaky distribution allows both sides to make game.

I don't think that bidding 4♠ is preemptive.
4♠ makes against most minimum hands, where E has no wasted values in hearts.

[barmar]

The point is that it doesn't bid game with only 23 combined points. The 12-card fit is overkill, and doesn't really add much to the combined value of the hands (once you get past a 10 card fit, those cards would usually be more useful as fillers in other suits).

With the above hands, game is only 50%, it requires the ♣ finesse. But change East's hand slightly, e.g. ♠AJT94 ♥Q ♦52 ♣AJT32 and 4♠ doesn't make. It turns out to be a good sacrifice, because South would still make 4♥ (in fact it makes 5♥). But on the assumption that South has a weak hand, there's no reason to sacrifice.

Now let's give East a really nice hand: ♠AJT94 ♥Q ♦AK ♣AJT32 (I swapped South's high ♦s and East's low ones, so now South has something more like his bid). If West bids 4♠, East will Blackwood into a no-play slam. It expects West to have something close to 13 HCP, not a minimum with a zillion useless spades.

It's true that in this case when West doubles and East leaves it in, NS only go down 1 non-vul when E/W can make a vulnerable game. What can I say? Preempts work, and it's better to go plus than minus.

[emalka]

barmar, on 2011-December-05, 20:39, said:

The point is that it doesn't bid game with only 23 combined points. The 12-card fit is overkill, and doesn't really add much to the combined value of the hands (once you get past a 10 card fit, those cards would usually be more useful as fillers in other suits).

With the above hands, game is only 50%, it requires the ♣ finesse. But change East's hand slightly, e.g. ♠AJT94 ♥Q ♦52 ♣AJT32 and 4♠ doesn't make. It turns out to be a good sacrifice, because South would still make 4♥ (in fact it makes 5♥). But on the assumption that South has a weak hand, there's no reason to sacrifice.

Now let's give East a really nice hand: ♠AJT94 ♥Q ♦AK ♣AJT32 (I swapped South's high ♦s and East's low ones, so now South has something more like his bid). If West bids 4♠, East will Blackwood into a no-play slam. It expects West to have something close to 13 HCP, not a minimum with a zillion useless spades.

It's true that in this case when West doubles and East leaves it in, NS only go down 1 non-vul when E/W can make a vulnerable game. What can I say? Preempts work, and it's better to go plus than minus.

33% game is good enough vulnerable at imps.
If GIB can't bid here 4♠ it should pass
Better to go smaller minus.

[gwnn]

barmar, do you really think doubling with 7-card support is reasonable because you don't preempt over a preempt?

[xxhong]

This rule is simply wrong. Deciding whether to bid 4S is usually based on the trump length, shape, not merely on HCPs.

With some shortness and 5 spades, usually 6 HCP would be enough. For example, you can bid 4S over 4H with AQxxx x xxx xxxx, because you have two ways to win, either they may make 4H and 4S would be cheap or you may make 4S and partner can't balance with double. It can be rather rare that they can't make 4H and you can't make 4S, especially against sane players.
Here, the range for 4S should be quite wide, from 8 total points to 16 total points IMO, it should be usually based on an offensive oriented hand and it is at the lower end, it should have some extra length in S.

barmar, on 2011-December-05, 16:23, said:

Over a takeout double, 4♠ is preemptive, so it doesn't need a strong hand.

Over 4♥, GIB needs 13 total points to bid game -- you don't preempt over preempts. With 11-12, it doubles to show almost-GF values.

GIB was fooled because South has a strong hand, not the week hand that was expected. The freaky distribution allows both sides to make game.

[Bbradley62]

Do we really need to post a poll in the "Interesting Hands" forum to convince you that this double is bizarre beyond belief?

[cloa513]

barmar, on 2011-December-05, 16:23, said:

Over a takeout double, 4♠ is preemptive, so it doesn't need a strong hand.

Over 4♥, GIB needs 13 total points to bid game -- you don't preempt over preempts. With 11-12, it doubles to show almost-GF values.

GIB was fooled because South has a strong hand, not the week hand that was expected. The freaky distribution allows both sides to make game.

If South didn't have the extra values, then North could have and it would have been almost exactly the same position.
If GIB was using Goren Total Points in raise bidding (which is 5 for void, 3 for singleton, 1 for doubleton) , then it would count 12-13 TP.

[barmar]

Unfortunately, GIB doesn't have the feature of re-evaluating a hand based on having a fit. Its total points are the same regardless of the auction. If we want to distinguish flat vs. shapely hands, and fit vs. non-fit hands, we have to do it with different bidding rules for each case. Or we allow simulations, and expect them to override silly bids like this. But in this case, the rule that says to double also has a flag saying that simulations are disallowed.

Looks like there are two ways we can go: 1) Add rules to raise partner with fewer points and long trumps; 2) Allow simulations to override the double rule.

But in either case, we need to reduce what the 4♠ bid shows, so that opener doesn't get too excited.