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by raydog » Thu Nov 03, 2022 4:28 pm
I spent a lot of time simulating and analyzing this, and finally have some results to share.
First let me say that if I came across this situation in live play, and had 10 sec. to decide, I would play the R. My reasoning is that, looking at the 7 cards I have seen, I know there are 5D + 4H + 3S remaining which my partner in S4 may hold, so they don't have a great chance of trumping in. And while playing the R is a bit of overkill (and I don't get to use it to take out other trump from the opponents' hands), the upside is that my partner will know where it is, which is generally a great piece of information for the declarer as they plan their play.
Second, let me specify the limits of my analysis (my simulator program) and why these results should be interpreted with a reasonable amount of skepticism (just how much is up to you to decide).
My program makes assumptions about:
1) when S4 calls trump? [this is the primary assumption; ultimately, when S4 has only 1 trump in hand (2 after they pick up the QC), my program is rather selective. I won't go into the details - there is a related post which deals more specifically with this, which I will analyze next. Suffice to say they don't call very often];
2) what does S4 discard? [this is not too hard, and I think I have it close to optimized. The primary considerations are getting void in a suit (preferably a green suit), and keeping any Aces. There are of course exceptions and specific borderline situations, but I trust my program on this];
3) when does S1 lead the AD? [once again, I think I have this optimized. S1 will lead the AD except when a) they have 3+ diamonds (unless that is their only non-trump suit); b) they have the AH, and that suit is equal in length or shorter than the D suit*; c) they have the AS, and that suit is shorter than the D suit]
4) how the hand is played in general (I tried to find the best play in a few common situations, as you will see below)
* this is a minor programming issue. Suits are analyzed in order, and H comes before D. So A singleton (doubleton) H won't be usurped by a singleton (doubleton) H. With A-9H and A-KD, better to lead the AD, but this entails a lot of programming for a very rare and marginally significant situation).
Clearly a big caveat. But I did discover some interesting things, and I think my results look reasonable and defendable.
I gave S1 the AD, gave S2 the JC + Q-10S + Q-10H, and set the QC as the turned card; all other cards were random. I also looked at 2 different scenarios: if S4 ended up with 2 trump or 3+ trump [perhaps a meaningless exercise, since S2 can't know how many trump their partner has, and so can't use that information in their decision making process, but it was interesting to compare the results].
Out of curiosity, I first looked at what suits S4 was void in, WHEN S4 declared AND S1 led the AD (about 18.4% of the hands).
When S4 had 3 trump (~16.0% of cases), they were void in:
S 63%
H 63%
D 39%
so 65% of cases they were void in 2 suits
When S4 had 2 trump (~2.4% of cases), they were void in:
S 54%
D 52%
H 26%
so 32% of cases they were void in 2 suits
Interesting how it shifts, but I'm not going to delve into that (though I do think I can explain the shift). This may explain some differences in play in the 2 cases later on [which, again, is academic, since S2 doesn't now how many trump S4 has, and S4 MOST LIKELY has 3 trump, as my simulator currently plays].
Let's say S2 trumps the 1st trick with the R. Now they have to decide what to lead on the 2nd trick.
If S4 has 3+ trump, what should S2 lead if S4 discards a:
D: lead 10H: (17,113 / 67,939 / 12,883) [sweep / 1 pt / euchred] EV = +0.78
lead 10S: (16,494 / 69,584 / 11,857) EV = +0.81 [fewer sweeps, but fewer euchres]
better to lead 10S, but difference not significant
H: lead 10H: (2,754 / 28,610 / 5,516) EV = +0.63 [fewer sweeps, but fewer euchres]
lead 10S: (3,136 / 27,610 / 6,109) EV = 0.59
better to lead 10H, but difference not significant
S: lead 10H: (3,237 / 18,854 / 3,381) EV = +0.73
lead 10S: (2,770 / 19,668 / 3,034) EV = +0.75 [fewer sweeps, but fewer euchres]
better to lead 10S, but difference not significant
If S4 has 2 trump, what should S2 lead if S4 discards a:
D: lead 10H: (1,182 / 9,616 / 809) EV = +0.89
lead 10S: (1,095 / 9,650 / 862) EV = +0.87
better to lead 10H, but difference not significant
H: lead 10H: (205 / 5,645 / 3,638) EV = -0.13
lead 10S: (252 / 4,707 / 4,529) EV = -0.41
better to lead 10H
S: lead 10H: (173 / 2,419 / 505) EV = +0.57
lead 10S: (108 / 2,165 / 824) EV = +0.24
better to lead 10S
There are some differences here, but not surprising, given that the suit(s) S4 is likely to be void in vary depending on how many trump they have. You can do the math to verify, but the end result is that, if S2 plays the R after S1's AD lead [18.4% of hands], and then leads either the 9 (H or S) on the 2nd trick, the EV is about 0.72. That's the headline number to remember.
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But what if S2 plays off on the first trick? Is it better to dump the 10H or the 10S?
Remember, the starting point is that S4 declared C trump, and S1 led the AD. If S2 plays off on the 1st trick, and anything but a D is led on the 2nd trick, S2's choice is clear. So we are only looking at cases where S1 wins the first trick with their AD, and then re-leads a D [there may be further considerations on the 3rd trick, but I didn't delve that far).
S2 discards the 10H, trick 1; D led by S1, trick 2; S4 has 3+ trump:
play R: (0 / 44,450 / 15,035) EV = +0.24
play QH: (0 / 49,453 / 10,032) EV = +0.49
S2 discards the 10S, trick 1; D led by S1, trick 2; S4 has 3+ trump:
play R: (0 / 44,482 / 15,015) EV = +0.24
play QS: (0 / 49,839 / 9,657) EV = +0.51
When S4 has 3+ trump, better for S2 to throw off the same suit and get void
S2 discards the 10H, trick 1; D led by S1, trick 2; S4 has 2 trump:
play R: (0 / 6,078/ 1,299) EV = +0.47
play QH: (0 / 5,025 / 2,352) EV = +0.04
S2 discards the 10S, trick 1; D led by S1, trick 2; S4 has 2 trump:
play R: (0 / 6,251 / 1,389) EV = +0.45
play QS: (0 / 5,272 / 2,368) EV = +0.07
When S4 has 2 trump, better for S2 to trump with R
Overall, since S4 is far more likely to have 3+ trump, if S2 plays off on the first trick, best to do the same on the 2nd trick, if they have the chance.
But in most instances, S2 will simply be following suit on the 2nd trick (after throwing off on the 1st trick). If we follow the above protocol (i.e., throwing off the same suit IF a S1 wins the 1st trick AND a D is re-lead), and otherwise following suit, the overall result is:
(10,138 / 151,589 / 23,031) EV = 0.68
This is lower than the 0.72 EV of trumping with the R on the 1st trick, so I stand by that play. BUT, the difference is small, so in the end, it all depends on how well you know your partner's and your opponents' play.
Last edited by
raydog on Mon Nov 07, 2022 12:55 pm, edited 1 time in total.