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EdwardPiwowar / BBA

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Missing negative double, and yet another: This is not a limit+ raise #622

Open ThorvaldAagaard opened 5 months ago

ThorvaldAagaard commented 5 months ago

07AB7526643F2E264EB47F54A986 image

North forgot to double - yes only 8, but 54, and a little support for partner, so being ready for 2H

After the double Souths 3D is showing a good hand (15+ HCP), and should bid 2/3S

EdwardPiwowar commented 5 months ago

Next BBA image

ThorvaldAagaard commented 5 months ago

Still missing the double in North

ThePokerDude commented 2 months ago

8642 - east's bidding is wrong. There is no reason to bid 6d. To overrule partner's decision to bid only game you need extreme extra values. A good hand is not enough. Here East has a good hand but no extreme extra values (such as void + 2 aces for example). image

ThorvaldAagaard commented 2 months ago

If 6D ever could be right, then 3D was wrong :-)

EdwardPiwowar commented 2 months ago

Next BBA image

ThorvaldAagaard commented 2 months ago

Now we have one of those. If opponents double we just pass instead of showing our hand

EdwardPiwowar commented 2 months ago

you did it on purpose... 3d, 4d and 5d are weak after double

ThorvaldAagaard commented 2 months ago

OK, but then we need a way to show a strong raise. Here it would be XX. But you can leave it as we have more expensive errors :-) I will check and close after next version

EdwardPiwowar commented 2 months ago

ok, but notice opps + pd have 32+ HCP - E can't have a strong hand.

ThorvaldAagaard commented 2 months ago

You have defined 3,4 and 5D as 2-4 HCP, actually I think that 5D (4 on a bad day) is the right bid

EdwardPiwowar commented 2 months ago

image

ThorvaldAagaard commented 2 months ago

Well, West went overboard :-)

ThePokerDude commented 2 months ago

After the double to 2D west has to show support. This is a fundamental principle of competitive bidding - show your support as fast as possible. Whether 3d, 4d or 5d - I'm fine with all of them. I'll tend to 3d or 4d as I like the law of total tricks. That's why I advocate for always raising to game with a 5card support to partner's 5card suit. But it is a personal preference.

Given the bidding in the last example I think there is a flaw in the algorithm of calculated bids. 1) as North's X denies 3 hearts it's likely partner has no void in hearts. 2) The chance north has a sigleton heart and can ruff is maybe 40% 3) The chance of partner having two aces outside of spades are pretty low - 20% maybe

Given 1+2+3 the chances of making 6d are lower than 20%, probably something like 10%. So we can assume 6d is not making.

Next question is - what are the chances of 5s making (and 6d being a good sacrifice)? How many spades do we expect partner to have? On average probably 4 Partner is short in hearts, so partner possibly can overruff if the oppenent has to ruff hearts So I'll expect to make on average: 1,5 spade tricks 0,5 heart tricks 0,5 diamond tricks 1 club trick

So the calculated bid should be to not bid 6d but to pass. Why not double? Because partner can much better estimate the number of spade tricks he expects to make. With xxx or xxxx he will not double. In situations where partner can have strong trump opposition we should involve partner in the bidding.

This is probably hard to put into code ;)

EdwardPiwowar commented 2 months ago

This is definitely hard to code ;) But the explanation is great.