Bypass spades?

[whereagles]

Hi all. Suppose you have your average minimum 12-14 balanced opener, i.e. something like..

 

Axxx

Qx

KJxx

Kxx

 

You open 1♦ and pard bids 1♥. Do you skip spades and bid 1NT to show shape/strength or do you prefer to bid 1♠? By skipping spades you have a very precise rebid available, but you run the risk of playing 1NT when a 44 spade fit was available.

 

I ran a quick simulation, assuming that:

- opener has a 12-14 rebid 1NT with 2-3 hearts AND

- you have some checkback mechanism that allows you to dig out the spade 44 fit if responder is invitational or better AND

- pard will take you back to hearts when he has 5 and is weakish

 

In this case, you land in a bad contract whenever:

- responder is 5-10 hcp and 44 majors OR

- responder is 5-10 hcp and is 45 majors and you have a doubleton heart

AND

- our side's hcp is 22 or less. With 23-24 the 1NT usually makes anyway, so no biggie.

 

The results, using Staveren's simulator for 10 million hands, were:

 

lost fit, bad contract: 0.0005805 = ~0.06% of the time!!

 

This is absolutely amazing. I would NEVER expect it to be so low. If this is true, it absolutely vindicates the theory of skipping the 4-card major.

 

The code for is below. Did I miscoded it??

----------------------

generate 10000000

opener1214 = hcp(south)>11 and hcp(south)<15 
[space] [space] [space] [space] [space] [space] [space] [space] [space] [space] [space] [space] [space] and shape(south, any 5332 + any 4432 + any 4333)
[space] [space] [space] [space] [space] [space] [space] [space] [space] [space] [space] [space] [space] and (spades(south)==4 and hearts(south)<4)

lostfit = hcp(north)>4 and hcp(north)<11 
[space] [space] [space] [space] [space] [space] and 
[space] [space] [space] [space] [space] [space] ((hearts(north)==4 and spades(north)==4) or (hearts(north)==5 and spades(north)==4 and hearts(south)==2))
[space] [space] [space] [space] [space] [space] and (hcp(north)+hcp(south)<23)
action
[space] [space] [space] [space]average "lost fit, bad contract" opener1214 and lostfit

---------------------

[Finch]

Haven't you calculated the probability that

{Opener has 12-14 and 4-4/4-3 in the majors} AND {responder has the lostfit}

 

rather than

 

{responder has lost fit} GIVEN that {opener has the relevant weak NT}

 

?

 

i.e. you need to calculate

 

[lostfit AND 1214] / [1214]

 

[FWIW I make the answer you are looking for about 4 or 5%

 

But I disagree with the assumption that this actually answers a useful question... ]

[Free]

Running this simulation makes you bid 2♥ on a hand with 4♠ and 5♥ all the time. I don't think you'll do this with a crappy ♥ suit, so some 5-3 fits will still be lost this way. This however is caused by the fact that you don't support with a 3 card :unsure:

[helene_t]

But I disagree with the assumption that this actually answers a useful question...

Well, if we accept the premise that the lost 4-4 fit in spades is the main disadvantage of bypassing spades, then it is relevant how frequent this is.

 

But:

- How bad is it to lose the 4-4 fit? Sometimes responder has a 10-count suitable for a trump contract and a good game could be bid if spades were not bypassed. Anyway, the notion that it's bad with 22 combined points and doesn't matter with 23 points is questionable.

- When responder passes 1♠, we may reach a playable 1♠ in the 4-3 fit while 1NT would have been more difficult.

- How does the fact that opps are silent influence the statistics?

- If we never bypass, opener's 1NT rebid becomes more stringently defined. This could be an advantage to the partnership itself (the check-back structure could be modified to benefit from that information). It could also help opps.

- Above all: how would you quantify the gain from bypassing spades?

[TimG]

- If we never bypass, opener's 1NT rebid becomes more stringently defined. This could be an advantage to the partnership itself (the check-back structure could be modified to benefit from that information). It could also help opps.

Lost in all this seems to be the corresponding benefit of 1♠ showing an unbalanced hand. If a partnership never by-passes, they may make life easier after a 1NT rebid; if a partnership always by-passes with a balanced hand, they may make life easier after a 1♠ rebid.

[kenrexford]

- If we never bypass, opener's 1NT rebid becomes more stringently defined. This could be an advantage to the partnership itself (the check-back structure could be modified to benefit from that information). It could also help opps.

Lost in all this seems to be the corresponding benefit of 1♠ showing an unbalanced hand. If a partnership never by-passes, they may make life easier after a 1NT rebid; if a partnership always by-passes with a balanced hand, they may make life easier after a 1♠ rebid.

This brings up a strange nuance here.

 

I have had discussions with a partner of mine about these types of sequences. We have agreed, and I think this to be a good agreement myself, that the priority of reliability as to a call in this type of sequence is:

 

1. Unbalanced (tendency COV or rebid problem)

2. Minor length

3. Major length

 

What this means is that a 1♠ bid will assuredly be unbalanced (COV/Rebid), that the minor length will always be 4+ and will almost always be 5+, and that the major length (spades) will usually be 4+ but may be 3-card if unbalannced with five of the minor.

 

This situation is not great for the example, but if 1♣-P-1♥-P-1♠, Responder can rely on unbalanced (COV/rebid) and on club length more than on spade length, as Opener may well be 3145, for instance.

 

In the actual, 1♦-1♥-1♠, Opener might well be 3154 with a COV in diamond-spade (weak clubs), for instance.

[whereagles]

Frances, I think you're correct. What I calculated is the percentage of ending up in the wrong contract in EVERY ONE of those 1 million hands, not just when opener is 12-14 bal, which is what I wanted. I'll redo the code tomorrow.

 

Thanks.

[whereagles]

Running this simulation makes you bid 2♥ on a hand with 4♠ and 5♥ all the time. I don't think you'll do this with a crappy ♥ suit, so some 5-3 fits will still be lost this way. This however is caused by the fact that you don't support with a 3 card :P

Well, where I play we hardly ever rebid 1NT without a bal hand, so responder is very likely to go back to hearts whenever he has 5 of them, regardless of suit quality.

 

As to supporting with 3 cards, it's also rare. Only I and pard do it.. lol :) And only if the hand is unbalanced and 11-14. Else we bid something else.

[whereagles]

Lost in all this seems to be the corresponding benefit of 1♠ showing an unbalanced hand.

That's exactly the point of bypassing spades: to make the 1NT rebid, which is a very precise bid, more frequent, along with increasing precision with 54s.

[TimG]

Lost in all this seems to be the corresponding benefit of 1♠ showing an unbalanced hand.

That's exactly the point of bypassing spades: to make the 1NT rebid, which is a very precise bid, more frequent, along with increasing precision with 54s.

If you make it more frequent it will be less precise.

[whereagles]

Lost in all this seems to be the corresponding benefit of 1♠ showing an unbalanced hand.

That's exactly the point of bypassing spades: to make the 1NT rebid, which is a very precise bid, more frequent, along with increasing precision with 54s.

If you make it more frequent it will be less precise.

Yeah, but NT bids/rebids can take a lot of beating before becoming unsound. Just look at people opening it on 5 card majors, 6m322s, 54s, etc and still winning :)

[mike777]

Frances, I think you're correct. What I calculated is the percentage of ending up in the wrong contract in EVERY ONE of those 1 million hands, not just when opener is 12-14 bal, which is what I wanted. I'll redo the code tomorrow.

 

Thanks.

I have no idea how you code this but ok.

 

How do you code for refinding or remissing the 4-4 spade fit when the opp do not let you play in 1nt, they balance over your 1nt?

 

I would be pretty shocked that not bidding one spade over 1h is a losing action and rebidding 1nt is the winning one.

 

2) I think assuming responder rebids 2h with all 5 card h suits is too big an assumption.

 

3) How do you factor in if you have to use cb now on these hand types and the opp double your cb bids and it hurts you?

[whereagles]

It's easy to code it. I'll put the code here tomorrow.

 

How often bypassing is a problem, we'll see. I will keep assuming responder will always pull with 5 hearts because that's standard here. Can also calculate without that assumption, if you're interested.

[mike777]

It's easy to code it. I'll put the code here tomorrow.

 

How often bypassing is a problem, we'll see. I will keep assuming responder will always pull with 5 hearts because that's standard here. Can also calculate without that assumption, if you're interested.

I have no idea how you code this but ok.

 

How do you code when you rebid 5h and when you do not?

How do you code when the opp balance and you may or maynot refind your 4-4 spade fit

How do you code the opp doubling your cb bid and it hurts you or does not hurt you?

 

These are not 100% or zero options. In other words how do you code for the opp maybe bidding sometimes and not bidding other times?

[whereagles]

Ok I recoded the stuff properly now. So now it gives the percentage of time we end up in a bad contract when opener is bal 12-14 with 4 spades and 2-3 hearts. Results were

 

lost fit, bad contract: 0.0288053

Generated 10000000 hands

Produced 198991 hands

 

So that's around ~3% chance of landing in a bad spot by skipping spades. This lowers to ~2.3% if you accept that 1NT on 21 hcp is a good contract, and to ~1.6% if you think 20 hcp is ok. Slightly lower than what one would expect in abstract (Frances guessed 4-5%). Of course, at matchpoints skipping spades can be costly, so this is more of an imps result.

 

I think I'll skip spades. After all, I've only seen one case at table where skipping cost... and it wasn't even me, it was opps. LOL. Below is the revised code.

 

-------------

 

generate 10000000

opener1214 = hcp(south)>11 and hcp(south)<15 
                          and shape(south, any 5332 + any 4432 + any 4333)
                          and (spades(south)==4 and hearts(south)<4)

lostfit    = hcp(north)>4  and hcp(north)<11 
                          and ((hearts(north)==4 and spades(north)==4) 
                               or (hearts(north)==5 and spades(north)==4 and hearts(south)==2))
                          and (hcp(north)+hcp(south)<23)

condition
       opener1214

action
       average "lost fit, bad contract" lostfit

[whereagles]

1. How do you code when you rebid 5h and when you do not?

 

2. How do you code when the opp balance and you may or maynot refind your 4-4 spade fit

 

3. How do you code the opp doubling your cb bid and it hurts you or does not hurt you?

 

4. In other words how do you code for the opp maybe bidding sometimes and not bidding other times?

1. You can code some assumptions. It's easy with Hans's dealer. I just assumed responder always bids 2♥ with 5 cards (even if it's xxxxx).

 

2. You could try and complicate the code in that case, but I didn't bother. I don't think that's relevant enough to change the main point of the results.

 

3. What's cb?

 

4. See 2 above.

[jvage]

I would seldom rebid a 5 card heart-suit, but that is a matter of style and how often partner supports with 3.

 

I think a more serious flaw with your approach is that it often forces responder to check for 4 card spades with invitational+ values. While the effect is almost impossible to simulate this will often help opponents significantly with their lead and defence compared to "standard" bidders who raise to 2/3NT directly. On the other hand you may "hide" a 4-card spade suit with opener, I'm not sure which is most important.

 

John

[barmar]

Lost in all this seems to be the corresponding benefit of 1♠ showing an unbalanced hand.

That's exactly the point of bypassing spades: to make the 1NT rebid, which is a very precise bid, more frequent, along with increasing precision with 54s.

If you make it more frequent it will be less precise.

But it's still far more precise than a suit rebid. If you never bypass, the 1♠ rebid has a HCP range of 12-18, and shapes anywhere from from 4333 to 6007.