3NT lead problem #12983

[whereagles]

Hi all, see if you get this one right.

 

Venue: open team trials, training session. Thus top opponents, obviously. IMP scoring.

 

[hv=pc=n&n=st643hq852dk876c9&d=s&v=e&b=3&a=p1cp1dp1hp2cp2sp3dp3nppp]133|200[/hv]

Auction:

1♣ = either (1) natural 4+ cards unbalanced or (2) preparatory with balanced 12-14 H (can be 2+ clubs).

1♦ = 4+ hearts.

1♥ = 3 hearts, normally min hand.

2♣ = GF relay.

2♠ = nat.

3♦ = stopper ask.

 

Yer lead?

[the hog]

small D

[eagles123]

spade

[Jinksy]

Small ♦ for me. A passed P's unlikely to have good enough ♣s to set the contract, and with LHO sounding balanced, P shouldn't have more than 3Ss, just in case I was feeling fanciful. If the D lead carves a trick, we probably weren't ever setting it.

[Lord Molyb]

small diamond for me too

[1eyedjack]

Hello

 

I chose that:

 

Declarer had 13-18 HCP. Outside that range he would either have made some further slam move or not game forced.

Declarer had fewer than 5 Spades and precisely 4 Hearts, or would have played in known major fit. Not guaranteed but close enough.

Declarer had fewer than 2 of top 3 honours in D (to justify asking)

Dummy had at least 1 of top 3 honours in D (to justify accepting)

Dummy had 12-14 bal with 4 Spades and 3 Hearts.

Partner completely random in context.

 

Dealt 10000 matching deals (took 15812246 deals to achieve it). D/D result of alternative leads are:

 

Lead ........ % set ......... Expected tricks

 

D8 ...........8.18% ......... 2.70

C9 ......... 6.16% ............ 2.59

DK ........ 6.02% ............ 2.32

S4 ........ 5.66% ............ 2.60

S6 ........ 5.64% ............ 2.60

ST ........ 4.51% ............ 2.51

H5 ........ 3.38% ............ 2.35

H2 ........ 3.37% ............ 2.35

H8 ........ 3.00% ............ 2.30

HQ ........ 1.15% ............ 1.93

 

 

 

 

 

[whereagles]

@1eyedjack: your constraints are a bit confusing. Opener is the declarer.. I think you got it the other way around.

[1eyedjack]

@1eyedjack: your constraints are a bit confusing. Opener is the declarer.. I think you got it the other way around.

 

You are right. My bad.

 

I have swapped declarer and dummy in the previous example and re-run.

 

Dealt 10000 matching deals (took 15674724 deals to achieve it). D/D result of alternative leads are:

 

Lead ........ % set ......... Expected tricks

 

D8 ...........6.15% ......... 2.61

C9 ......... 5.34% ............ 2.57

S4 ........ 4.93% ............ 2.57

S6 ........ 4.86% ............ 2.56

DK ........ 4.50% ............ 2.20

H2 ........ 3.30% ............ 2.41

H5 ........ 3.23% ............ 2.40

ST ........ 3.00% ............ 2.33

H8 ........ 2.68% ............ 2.35

HQ ........ 1.60% ............ 2.18

 

 

 

[Lord Molyb]

@1eyedjack: in which scenarios would the ♠4 lead gain over the ♠6? :huh:

[1eyedjack]

@1eyedjack: in which scenarios would the ♠4 lead gain over the ♠6? :huh:

 

Hmm, I could have exported the output into a pbn file, loaded it into DDS, filtered the 10K hands as much as possible and then hunted through the remainder, for what appears to be the single hand that makes a difference, based on the spread of %.

 

Not going to attempt that. Not sure that I can reproduce the data if I fail to pbn it first time. That is a more interesting point, actually, and will look into it. Need to be able to save the random number seed in the .ini file.

 

My guess is that declarer had 4 card Spade suit including the Spade 5. Leading the 6 somehow promoted the 5.

 

 

 

[whereagles]

So that seems to have settled it: diamond is the winner.

 

And it is so in practice, because opponents had ♦Jx in dummy opposite declarer's "stopper" which consisted of ♦Qx tight :)

 

If you were to "try" for something more fancy, like leading the club 9 on grounds that pard "could have doubled 3♦ with ♦AT9xx", you'd end up seeing declarer making an overtrick :) Two things warn against this: (1) pard is a passed hand, so you're probably not going to beat this on a passive lead, and (2) partner had a chance to double the 2♣ relay with a bunch of those.

 

Thx all.