[nullve]

Free, on 2015-July-23, 09:35, said:

Must be fun to play multi vs mushroom: 2♦ = I also have a long Major. Bye bye continuations for opps

I think Multi 2D vs. Multi Squared/MuSHroom is a good idea (and I believe an adaptation of something like Multi vs Multi or Granovetter's Best Defence to Multi may be the way to go), but you seem to tnink that

* After 2C-(2D[=Multi]), I need to say bye bye to the kind of continuations I use after 2C-(P).

This is not true, because it's certainly possible to play "system on" with X replacing the 2D relay. You also seem to imply that

* After 2C-(2D[=Multi]), saying bye bye to the kind of continuations I use after 2C-(P) will somehow hurt.

This is also wrong, because the 2D overcall enables Responder to pass many potentially misfitting hands with < inv values, to the point that he no longer needs a mechanism to find out whether Opener has 6 M or 5M4+m on partscore deals. In other words, there's no reason, other than simplicity, to play "system on" here.

[Zelandakh]

I think you will find he is saying that after 2♣ - X, showing one major or a strong hand, you might find things awkward. Since you have not yet commented on how you change your responses after a double, that is difficult to comment on.

[gwnn]

Provided that he chucks the multi rebid by opener I can't see how it will not be better than opps passing throughout.

[nullve]

Zelandakh, on 2015-July-24, 18:06, said:

I think you will find he is saying that after 2♣ - X, showing one major or a strong hand, you might find things awkward. Since you have not yet commented on how you change your responses after a double, that is difficult to comment on.

gwnn, on 2015-July-25, 00:21, said:

Provided that he chucks the multi rebid by opener I can't see how it will not be better than opps passing throughout.

Instead of chucking the 2M rebid, I've so far played "system on" after 2C-(X), except that

2C-(X)-?:

P = intending to play 2CX opposite 4+ C

P = 4+ C

XX/2D+: never agreed on anything here, but in practice maybe:

XX: not sure (SOS with 5M3OM4D?)

2D = 4+ D

2M = 6 M

XX = long suit (particularly useful when Responder wants to get out in 2D)

any = P/C

Two posts ago I argued that 1M3OM is conceivably a problem of the type discussed only when Responder has about 8-15 hcp and either 1M3OM(54) or 1M3OM(63). But after 2C-(X), Responder may pass with 1M3OM(54) or 1M3OM36, intending to play 2CX opposite 4+ C, and redouble with 1M3OM63, intending to play 2D.

[glen]

Quote

... 13 hcp and 1M444 shape. Then he will happily play 2M opposite 6 M, but rather play 3m on a 4-4 fit than 2M on a 5-1 fit opposite 5M4+m. So instead of responding, say, 2S (still P/C, but now virtually never done without doubleton spades), he starts by relaying 2D. Then, if Opener rebids 2M, showing 6 M or 5OM4+m

Thus these two hands bid 2♣-2♦-2♠-Pass:

2♣ Opener:
♠ J7
♥ AQ942
♦ 10
♣ QT653

Responder:
♠ 3
♥ KJ53
♦ AQ65
♣ K984

Consider the size of the IMP swing if vulnerable

[nullve]

glen, on 2015-July-25, 15:14, said:

Thus these two hands bid 2♣-2♦-2♠-Pass:

That's correct.

[nullve]

I did a 100 deal simulation on BBO today with the following constraints:

N: 0-9 hcp and either 6M3-OM or 5M3-OM4+m*
S: 8-15 hcp, 1444

Assumption: N is dealer and EW pass throughout.

Result: 11 accidents (i.e. S passed 2S when N had 5H4+m), which was actually a lot less than I expected. This is what they looked like:

30) N: K98-QJT65-2-QT43 E: QJT3-A3-Q943-A76 S: 4-K972-AT65-KJ82 W: A7652-84-KJ87-95 DD result: 2S-3 Par: 4H=(NS)/4SX-2(EW) [i.e. depending on vul]
31) N: A92-T9854-void-T9863 E: KQT863-3-J732-AQ S: 7-KQ62-AT96-KJ52 W: J54-AJ7-KQ854-74 DD result: 2S-5 Par: 5HX-1(NS)
44) N: K3-97643-A5-Q432 E: QJ98-K-86432-KT9 S: 6-AT82-QJT9-AJ65 W: AT7542-QJ5-K7-87 DD result: 2S-2 Par: 4H=(NS)/4SX-3(EW)
57) N: JT8-AK964-8-T972 E: K53-52-AQT94-A85 S: Q-Q873-K765-QJ43 W: A97642-JT-J32-K6 DD result: 2S-4 Par: 3S=(EW)
62) N: K76-T9432-T964-6 E: T43-Q5-J87-AT982 S: 5-KJ76-AQ32-KJ43 W: AQJ982-A8-K5-Q75 DD result: 2S-4 Par: 3S=(EW)
77) N: T62-K7642-J732-Q E: KQ5-A853-K98-KT5 S: 4-QJT9-AQT6-AJ93 W: AJ9873-void-54-87642 DD result: 2S-4 Par: 4SX-1(E)
90) N: T8-AT752-42-QT76 E: AKQ7532-K-AQ9-85 S: 4-Q983-KT73-A943 W: J96-J64-J865-KJ2 DD result: 2S-5 Par: 4S=(EW)/5HX-2(NS)
95) N: T72-97532-AKT5-9 E: AKJ43-void-J732-AQT2 S: 9-AQ84-9864-KJ53 W: Q865-KJT6-Q-8764 DD result: 2S-4 Par: 3S=(EW)
96) N: T-T8742-KJT-QJ74 E: AQJ7543-KJ5-Q75-void S: 8-AQ93-A942-965 W: K962-6-863-AKT82 DD result: 2S-6 Par: 4SX-1(EW)
99) N: 642-AT542-9872-J E: AK9873-97-Q3-A98 S: J-KJ63-JT54-KT54 W: QT5-Q8-AK6-Q7632 DD result: 2S-6 Par: 4S=(EW)/5HX-3(NS)
100) N: T8-Q8643-T9-AQ92 E: K93-K7-KQ532-T65 S: Q-A952-AJ74-8743 W: AJ76542-JT-86-KJ DD result: 2S-4 Par: 3S=(EW)/4HX-1(NS)

(Yes, the 29 first deals were accident-free!)

Note: The DD and par results were (quickly) calculated by me. Check them if you want.

*Although I've described 2C as showing 6 M or 5M4+m, I don't really open 2C with 6M4+OM or (54)(40). Also, I don't use 9 hcp as the upper limit regardless of shape, so the above constraints on North are somewhat simplified.

[gwnn]

11 is a lot less than what you expected? I mean if I toss a coin (not look at my hand at all) I can already get 50 of them right so I am not sure what you expected add in the fact that a lot of the time your partner doesn't bid 2D but pass/corrects and then of course it's much better than tossing a coin no? I thought the point was comparing opener's second multi bid to just a simple natural rebid. How many times did your responder reply 2D out of the 100? How many times did you successfully avert a bad fit (5-1, not 3-1!)? Yes I know that you freed up the 2M openers to something else so there are benefits but right now we're discussing the costs.

[gwnn]

Oh you put 1444 specifically for S so he always bids 2D. that's nice but why not just do 100 deals and have him be 12, 13, 14, or anything whatsoever? I don't quite know what you're trying to measure. Just do an honest long simulation and report it.

Ps: I've alluded to this a few times but never directly asked you: are you really gonna open this also when vulnerable?

[nullve]

gwnn, on 2015-July-30, 07:19, said:

Oh you put 1444 specifically for S so he always bids 2D. that's nice but why not just do 100 deals and have him be 12, 13, 14, or anything whatsoever? I don't quite know what you're trying to measure. Just do an honest long simulation and report it.

I was zooming in on one of the conditions under which the 2C-2D; 2M mechanism threatens to collapse, as in glen's example. (Doesn't happen easily when Responder is 0-7 or 16+, I think) I honestly don't know what an honest long simulation would look like, since people tend to want to be able to overcall but I don't want to force a set of agreements upon them. But I thought this 100 deal simulation could still serve as some sort of (qualitative) illustration of what to expect under the given conditions. Just keep in mind that:

The accidents in 30) and 57) wouldn't have happened if East had doubled, Dixon-style.
The accident in 31) wouldn't have happened if East had made a normal-looking 2S overcall
The accident in 44) wouldn't have happened if West had made a normal-looking, but marginal, 2S overcall
The accident in 62) wouldn't have happened if West had made the kind of double you were talking about in an earlier post.
The accident in 77) wouldn't have happened if East had doubled, Dixon-style, or overcalled 2N
The accident in 90) wouldn't have happened if East had acted with his very strong hand
The accident in 95) wouldn't have happened if East had made a normal-looking, but IMO misguided, 2S overcall
The accident in 96) wouldn't have happened if East had made a normal-looking S overcall (either 2S, 3S or 4S)
The accident in 99) wouldn't have happened if East had made a normal-looking 2S overcall or West had made a "gwnn-style" double

So if EW were playing normal bridge (instead of passing throughout), as many as 10 of the 11 accidents could have been avoided. The ones in 90) and 99) even benefitted NS.

Quote

Ps: I've alluded to this a few times but never directly asked you: are you really gonna open this also when vulnerable?

In the "lab" I currently require 6M (i.e. 6M3-OM) or 5M5+m when vulnerable. But that's (the current) me.

[gwnn]

How do you defend against a weak NT double? You didn't discuss this yet. So you are going to go back to normal bridge when your opponents bid but stick to bizzaro bridge when they pass? I will likely pass a lot in that case except to double with a weak NT or very strong hand (definitely not hand 62) and sit back and see if it's really 11% or something a lot higher (you should try it also with the 12's and 13's). Vulnerable it seems completely insane to me but ok if you have 5-5 I guess playing the 1-3 or 0-3 fit will go better. Sorry don't mean to be hostile but I still don't understand how you can think that this is a good idea (other than the fact that it's yours).

[nullve]

gwnn, on 2015-July-30, 12:30, said:

How do you defend against a weak NT double? You didn't discuss this yet.

Not specifically, but see post #64.

Quote

So you are going to go back to normal bridge when your opponents bid but stick to bizzaro bridge when they pass?

Sort of. Unless pass shows something crazy, but we've already discussed this.

Quote

I will likely pass a lot in that case except to double with a weak NT or very strong hand (definitely not hand 62) and sit back and see if it's really 11% or something a lot higher (you should try it also with the 12's and 13's).

I do expect to be less lucky next time. Regarding the hand in 62), I was just trying to use the following defence:

gwnn, on 2015-July-21, 05:39, said:

double 2D with any 12-14 balanced or 16+ (simple enough and many people play these methods)