Another Compound

Dlr E
Vul NS
IMPs

	♠ A 8 7 3
	♥ A Q 10 2
	♦ K 7 6 5
	♣ 6
	♠ K 2
	♥ K J 8 7
	♦ A J
	♣ A K Q 10 4

West	North	East	South
		3♣	3NT
5♣	6♣	Pass	7NT
All Pass

♣3 led. RHO puts up the Jack. How do you play?

FWIW, RHO is an honest customer, LHO not so much. You can confirm this by playing another club.

My line and further analysis is below.



I tested one more club and LHO pitched ♠4 (I pitched ♠3 from dummy). Then 4 rounds of hearts, LHO following up the line, while RHO pitched ♣7, ♠5, then ♦4.

There's definitely a squeeze available at this point, but I still haven't committed to which one to play for. ♠K drew the Jack from RHO and 6 from LHO. Now I can afford another club before making up my mind: LHO pitched ♠9 while RHO followed with the 5. This is the ending:


 

	♠ A 8
	♥
	♦ K 7 6
	♣
	♠ 2
	♥
	♦ A J
	♣ 10 4

RHO is down to a club stopper and 3 pointed cards. If he started with 4 spades (and so still has that suit stopped), LHO made a very tricky pitch from 3=4=5=1 at trick 2 (and again on the last trick). Not to mention that the aggressive 3♣ opening seems much more likely with 4 diamonds than 4 spades. So, I played a spade to the Ace, and when RHO showed out I claimed: he must pitch his diamond guard here, then ♦A, ♣10 squeezes LHO in diamonds and spades.

If I had thought that RHO guarded spades but not diamonds, then ♦K, ♦A, ♣10 would effect a similar squeeze.

Technically this was just a double squeeze (LHO guards spades, RHO guards clubs, both guard diamonds), but if RHO had started 3=1=3=6 it would have been a true compound (a Type-R Unrestricted).

How about the defense?

East is going to need to make 2 pitches on the hearts, and then declarer is going to need to guess which of the pointed suits East still guards. If, as on the actual hand, East pitches one from each suit, he'd better not have started 3=3 or declarer cannot go wrong. On the other hand, even though East has had to make 2 pitches, always pitching one from each reveals nothing about which suit started longer. If West also pitches one from each suit (he has to make 2 pitches on clubs), declarer faces a straight guess (ignoring the auction), even though this is (or at least looks like) an unrestricted compound.

In compensation, if East did start 3=3, he must pitch 2 from a single suit, and declarer will almost always go right by playing that suit to now be unguarded. When East is actually pitching 2 from a 5 card suit (which he should do instead of 1 from each), declarer should normally go wrong (3-3 vs 5-1 is 25:3 a priori, though knowing an opponent's preempting style might be enough to overcome that).

I guess when the layout is such that it's not a true compound, just a double, that the position-tightening does not actually put anyone under pressure and so it makes sense that proper discarding reveals virtually nothing. There's always a double squeeze present, but it's more or less a toss up as to which to play for if both defenders are perfect. In contrast, when it is a true compound, East is squeezed twice and his discards are much more revealing, making it around 80% that declarer gets it right even against perfect defenders.

Obviously in practice a psuedo-squeeze is much more likely than this layout and West should be minimizing the chance of screwing that up.

Some minor technical points:

1. I should not have played a club at trick 2. RHO might not appreciate what is going on and if he pitches 2 clubs I'm spared any guess.

2. If I do play a club, I might as well pitch a heart. LHO might have trouble pitching from a 4 card holding in diamonds or spades. Also, I might as well play a 3rd (but not a 4th!). This gets more information from LHO early, without really helping RHO much if at all.

3. When crossing back to hand, I should probably use ♦A in case the ♦Q has been bared.

Finally, the ♦J was not strictly necessary, but it does help slightly in constraining the defense. Earlier I suggested that LHO pitching a spade early (and another later) from 3=4=5=1 would be tricky. This follows the general "principle" (technically this principle is false, but that's another post) of not waiting to the last possible moment to release a guard if you're squeeze. Since West is going to be squeezed in diamonds and spades later in the hand, if he anticipates this he has a good chance of leading declarer astray by pitching from his shorter suit early. However, thanks to the ♦J, he actually can't get away with pitching 2 diamonds (he started with Qxx). At double dummy the clash menace is irrelevant, but at single dummy it puts additional constraints on the defense and may make reading the position slightly easier.




The BBO record is here.

Read more!

Finesse played as a suicide compound

	♠ A 10 3
	♥ A 4 2
	♦ Q 7 6 2
	♣ A 9 8
♠ Q 9 2		♠ J 7 5 4
♥ 6 5		♥ J 10 9 8
♦ A K J 10 5		♦ 8 3
♣ Q 10 2		♣ J 5 3
	♠ K 8 6
	♥ K Q 7 3
	♦ 9 4
	♣ K 7 6 4

West	North	East	South
1♦	1NT	Pass	2♣
Pass	2♦	Pass	3NT
All Pass

♥J led. I ran this to my ace and crossed to dummy with another heart to lead a diamond. The Q was allowed to hold, then I exited a diamond. When West ran diamonds, East had to pitch 2 more black cards in this ending:

	♠ A 10 3
	♥
	♦
	♣ A 9 8
♠ Q 9 2		♠ ? ? ?
♥		♥ 10 9
♦		♦
♣ Q 10 2		♣ ? ? ?
	♠ K 8
	♥ Q 7
	♦
	♣ K 7

East must unguard a black suit. Win West's continuation with a king in dummy, then cross in the suit East doesn't guard and back to dummy's remaining K. One of these tricks will squeeze East again in the other black suit and hearts, then ♥Q will squeeze West in the black suits.

As shown, West could defeat this by exiting without cashing all diamonds. In practice, though, I held ♠J (you did notice the very light 1NT overcall, right?) and could always fall back on that finesse.

The BBO record is here.

Read more!

Alternate threat compound with variations

This is from Problem 6 from the August (2002, I think) Pav problem set. I think it was played in the European Championships sometime before that:

Axx
AKx
AKx
Axxx
 
QJx
QTxxxx
xxx
x
 

LHO opened 1C and you land in 6H. CK led. How do you play?

Duck (creating that Ax/void basic menace that's often useful), ruff the 2nd, play SJ forcing LHO to cover (or you'll have a black suit squeeze), then run trumps coming down to:

 
x
-
AKx
Ax
 
Qx
x
xxx
-
 

Clubs is the basic menace (vs West), spades is the alone ambiguous menace, and diamonds is the ambiguous menace with the basic menace, except that South has an alternate threat. If West has unguarded spades, the extra entry in diamonds is needed to get the CA out of the way before coming back to hand and cashing the last heart for a simultaneous type R.

If West unguards diamonds, the diamond threat in dummy is not useful because of entry problems, but this can be overcome by using the alternate diamond threat in hand. Note that the recessed club menace is key to make room for that alternate threat. In fact, that's a general feature of alternate threat compounds: the basic menace needs a winner that is not useful as an entry such as shown, or AKx/x, or Axx/K, etc.

This deal has an alternate solution – cash all the red winners coming down to:

    Axx
    -
    x
    Ax
Kxx      T98
-        -
Q        Ji
QJ       x
    QJx
    xx
    x
    -
 

This was an alternate threat squeeze where clubs was the basic threat, diamonds alternate, and spades the alone ambiguous threat. Get rid of the diamond entries, though, and it still works because West can’t keep pitching spades (the alternate threat is still important, though – in fact, the original threat is idle). Play 2 hearts pitching a diamond and then (unless it’s good) a club. West can’t bare the SK or the spades will run, so he must pitch a diamond and a spade. Since he can’t duck the SQ, it’s basically a B1 with the R (diamond) winners already out of the way. This spade menace is fairly strange, neither guard nor clash. I think it's a "shortstop" menace.

Switch the SQ and SK and it’s just a simple black suit squeeze. Do that but also switch the SJ and ST and it’s a compound guard squeeze (Type-R Guard-O in my classification -- R since the basic threat is alone (the diamond and 3rd spade with North are both idle), O since the guard menace is opposite the basic threat).


Read more!

Another NY Times compound

This deal is from a recent NY Times column:

(When I checked, the full deal appeared wrong, but the end position was right. Some spots in the full deal may be misplaced in my diagrams):

		♠	A 6 4 2
		♥	Q 10 5 4
		♦	K Q 10 8 4
		♣
		♠	K 9
		♥	A J 8
		♦	A 6 2
		♣	A K Q J 4

Trying for a BAM win, you land in 7N. At the table, declarer ran some diamonds and some clubs, discovered RHO had a club guard, unblocked the HQ and came down to:

		♠	A 6
		♥	10
		♦	8
		♣
		♠	9
		♥	A J
		♦
		♣	4

Declarer played a spade to the Ace and when RHO showed out he was able to play it as a double squeeze: cash the last diamond forcing East down to 1 heart, pitch the last club, and now West is also down to 1 heart.

This is pretty enough, but is not really any better than the heart finesse or stiff K with West. If West had had the HK, East would not unguard spades and expose West to the major suit squeeze.

Could declarer have done better? ...


In practice, I don't think so. But in theory, if he knew early enough that East had the club guard (for example if West shows out on the 3rd round), then I think a different line of play would be better. Details below the fold.




I think declarer wants to reach this position with the lead in the North hand:

		♠	A 6 4
		♥	10 5
		♦	8
		♣
		♠	K 9
		♥	A J
		♦
		♣	J 4

By not cashing the 4th club winner (impractical single dummy if both follow to the first 3) there's room for an extra heart with North. This will also require a spade entry to South in some variations. Presuming RHO still has a club guard, that only leaves room for 4 major suit cards, thus he can no longer guard both majors. If you judge that hearts have been unguarded, cash the last diamond pitching a heart, HA, CJ for a double squeeze around spades. If spades are unguarded, SK, CJ (pitching a heart), SA, diamond for a double squeeze around hearts.

This is an alternate threat compound. Cashing the CJ too early wrecks it by squeezing North.

What about the odds? Say RHO shows up with 6 clubs and 2 diamonds. He's going to pitch 1 club and 1 major before you make your decision and you should play for the major he pitches to be unguarded. The layout where you rate to go down is when he's 4=1 or 5=0 in the majors and pitches a spade, which happens about 19% of the time by my math (less a couple percent for stiff HK). Or, if he's 2=3 in the majors and pitches a heart, another 32% or so. So, in fact, this is a virtual toss up compared to the finesse.

On the other hand, there's some scope for misdefending on the compound line. I think, though, that restricted compounds rate to be hard to read in general and not much better than finesses. Of course, if you don't have those nice middle heart honors, the compound is still about 50% and there's no other line.

How could this be unrestricted, allowing you to cash an extra diamond before committing to deciding which major East has unguarded? A good start would be to move the SK to North (and a small spot to South). Now you don't need that 2nd heart in dummy, can cash all the clubs and then finish diamonds coming down to:

		♠	A K 4
		♥	10
		♦
		♣
		♠	9
		♥	A J
		♦
		♣	4

Now you'll have seen 2 major suit pitches from East. If he pitches 2 from the same major, you only lose to 5=0 or 1=4, both very unlikely. If he pitches 1 from each, you have to guess whether he was 4=1 to begin with or 2=3. You'll guess the latter, and wind up making something like 80% of the time.

Read more!