mikeh, on 2023-April-02, 23:29, said:
I’m rambling. I have a nasty second bout of Covid and played 48 boards of KO today, so I’m excusing myself�� I hope you will too. Despite my quibbles, I applaud your efforts.
I'm sorry to hear that, get well soon! You raised a lot of good points and I'll do my best to give some brief answers to each of them.
mikeh, on 2023-April-02, 23:29, said:
I second the commendation. I lack the skills needed to do this sort of thing, and the inclination to do it even if I could, but I expect there’s some useful information there
I do wonder, however, about the constraints.
Computer simulations are always going to have a number of unrealistic constraints. Personally I view this as two imperfect windows into bridge - one is our experience (maybe from playing in person, maybe from observing others). That part is obviously representative of actual play, on account of being actual play. But it suffers from biases due to imperfect memory, low sample size and even limited access to viable alternatives (most methods don't spread beyond a local circle). On the other hand computer simulations allow us to drastically increase the sample sizes on any question we may have (I typically simulate up to 100,000 relevant hands each for the frequency questions, or 1,000-10,000 relevant hands for the Double Dummy questions - this typically requires generating in the ballpark of 100,000,000 deals as any particular auction is very low frequency) and collect any form of statistics we like. In return there are issues with comparing simulations to actual play - humans don't play double dummy, their bidding decisions are not based on optimal criteria, judgement and hand evaluation are nigh impossible to program (and I haven't tried) and more.
I use these simulations as metrics of sorts to support or refute ideas based on personal experience. For example, if partner opens a 14-16 NT, we have a 3=4=3=3 with 10 to 15 points inclusive and opener has exactly 4 hearts (which responder doesn't know yet but can presumably find out through a Stayman auction), the simulation says that 3NT will make double dummy 66.8% of the time while 4
♥ will make 63.2% of the time. My conclusion is that this is basically a wash, and you may as well blast 3NT and avoid the information leakage. That's not a particularly brilliant insight, but I think a simulation can definitely help gain more understanding of good choices and methods.
mikeh, on 2023-April-02, 23:29, said:
For example I play T-Walsh with two partners, but with very different methods beyond the 1C 1R start.
When you look at frequencies, what parameters do you use for the opening bid? 2+ or 3+…my two partners prefer different styles
Do you assume 1D on 3343 or 4243 etc? In one we open all balanced hands out of range for 1N with 1C…not with a five card major but 3=3=5=2 is definitely included. In the other, we open 1C with 4=3 minors only if 3=3=4=3.
How light do you assume for a response? Today I held xxx Jxxxxx xxx x. Partner opened 1C, 2+. To us, this is an obvious 1D, showing hearts. We don’t play 1C as forcing and it’s often 11 hcp, but we virtually never pass it without club length. We’re sort of protected from most disasters because he bids 1N with 17-19, 2-3 hearts and never bids 4H unless 5=6, where I’d be delighted. We use 2N as a gf raise, and I can transfer and pass 3H should I choose.
You say you are working on frequencies of opponent hand types after 1C P 1S, assuming that 1S denies a major. I don’t play that in either of my partnerships.
1S denies a major unless responder has longer diamonds and a game force hand…while the ‘no major’ holdings are far more common than the ‘longer diamonds, gf’ hands, I think you’d be overestimating the frequency of 4th seat holding both majors if you didn’t recognize that. Maybe there are people who use 1S to deny a major, but I think that is an unnecessary complication, making relative major-minor length more difficult to assess when we own the hand.
I've deliberately postponed the T-Walsh questions because there are so many different T-Walsh methods. Your point on 1
♠ is well taken, I did mean a method where 1
♠ may have a major and longer GF diamonds, I simply failed to specify this in the question statement. My intent was to assume 1
♣ on any balanced hand out of 1NT range without a 5-card suit outside clubs, e.g. including 3=4=4=2 hands. I also think that any weak hand with long hearts (in fact, most 0-point 5-card hands) are clear 1
♦ responses - as you say you can handle any response. One of the important preliminaries to answering T-Walsh questions is specifying an exact T-Walsh method(/system), and I haven't gotten around to that yet. But my intent is to include:
- Open 1♣ on (almost) all balanced hands outside 1NT range - i.e. only excluding 5332 hands with the 5-card not being clubs (personally I wouldn't mind including 5♦332 as well).
- Respond even on very weak hands with a long major, protected by the knowledge that partner will accept the transfer with weak balanced hands and will bid 1NT with strong balanced hands, and won't jump around very often.
My main concern are the 1
♠ through, say, 2
♠ responses. Nearly every partnership seems to have their own set of rules for them.
mikeh, on 2023-April-02, 23:29, said:
Also, and I may be betraying my ignorance here, knowing (say) the probabilities that the opps should pass us out in 2M after 3 passes doesn’t seem, to me, to have real world implications
After all, based on probabilities, it’s never right to open 7N but what if I held 13 winners, with the ace of every suit? I can just imagine the post game discussion. I didn’t open or later bid 7N because it’s almost impossible for me to hold this hand.
More difficult, I’d think, is to set minimum parameters for possible balancing actions in terms of shape and hcp, and then simulate those parameters. One might, I think, come up with something like….after 2S p p…if one holds 2=3=4=4 11 hcp one is slightly better off to pass than to double (or maybe the opposite) while with 1=6=3=3 8-9 hcp one is slightly better to bid 3H, or not..and so on.
I pick up QJ9xx Ax Jxxx xx, I don’t much care that ‘most of the time, ignoring what one holds, one should not pass out 2S’….because bridge decisions are based on hands, not relative likelihood of having the near infinite shapes one might hold. Knowing that passing is usually better than bidding, or vice versa, doesn’t tell us anything about what to do with many of the hands we may hold.
Where frequency of hand types really comes into its own, imo, is in system design, especially in the design of artificial methods. When I played relay, our system (which I most assuredly did not design) was explicitly designed to maximize the bidding space of frequent patterns rather than freaks. It meant showing a 1=5=6=1 hand after a 2C relay to 1D took up a huge amount of bidding space but 4432, 5422, 4333 etc were economical to show, which allowed for relays that could, on some hands, show the precise pattern and every card of Jack or higher.
The "how often should they pass us out" metric is not useful at the table. The purpose of that question is to aid in system design. For example, even over my aggressive 2
♠ opening (which is a 5-card suit more often than not) it seems the opponents can theoretically get a good score by passing me out while nonvul only 2.40% of the time, while they can get a good score by passing me doubled and vulnerable (if I would not change my suit requirements under those conditions) 26.0% of the time. I use these figures as an imprecise metric to determine how aggressive my weak twos should be, based on position and vulnerability. At some point I intend to write a followup specifying what direct and balancing doubles look like, what penalty passes look like, what runout sequences look like and verify how frequently I might actually get passed out (un)doubled - but it helps to know at least in theory how often they
could catch me speeding, given perfect information.
Frequency information on relay auctions is really useful (and, ironically, usually inaccurate - conditioning on the opponents not having an overcall and the partnership having enough combined strength for a GF auction has a noticeable impact on the hand frequencies, so most textbook/a priori frequencies are actually wrong). This is part of why I looked into, among other things, the IMprecision auctions.
mikeh, on 2023-April-02, 23:29, said:
Also, and it seems clear that you know this, this work will likely confirm that 14-16 is a far more common strength, in a balanced hand, than 15-17, thus encouraging the ongoing shift away from 15-17 1N.
A traditional 14-16 NT covers approximately 6.40% of all hands, which increases to approximately 8.02% if we include a host of semibalanced hand types. For 15-17 NT the figures are 4.84% and 6.23% respectively. This represents an increase of approximately 30% for the lower range, although there is a slight adjustment when we consider seating. The other three players will more frequently have an opening conditional on us holding 14-16 compared to 15-17, so a slightly smaller fraction of the times you do hold a strong NT you won't get to open it with the weaker range.
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