The Tao of Gaming

Boardgames and lesser pursuits

Musings on Bridge Bidding

(This is probably not of interest to non-bridge players. Tough. Learn to play).

Over the course of the years, I’ve read quite a few bidding systems. This week I read Marshall Miles book “The Unbalanced Diamond.” It’s interesting, particularly the aforementioned diamond bids.

Standard American (at least, the 2/1 variety that most experienced tournament players use) actually handles things quite well, but it’s interesting in that there is only one strong forcing opening (2 Clubs).  Precision (and other Big Club systems) also only have a single strong forcing opening, but it has to handle moderately strong hands (16+) as well as the huge hands that 2 clubs openings cover.

[I’m ignoring the 2 No Trump opening which shows 20-21 in most systems, and any openings above 3 Spades. Some tournament players tack on some openings to show a long major suit that can almost make game (The Namyats convention) OR 3NT to show a long running minor. And some hands can just open Blackwood, to ask about aces].

So what’s interesting to me is seeing systems that have multiple ‘big opening’ hands.  The Unbalanced Diamond actually has three big opening hands, 1C usually shows 15-19 (strong, but not overwhelming hands) but can include a few well defined hands that show more. (24-27 point balanced hands, and game forcing hands with both majors), 2 Clubs shows 20+ hands with a five card major (or two), 2 Diamonds shows 20+ hands without a five card major (excpet hands that are exactly 22-23, with 5332 distribution).

In the old days, of course, any 2 bid was strong. Four strong opening bids (for 20+ point hands). The problem is that these hands are pretty rare. Better to condense all strong bids into 2C (and use the rest for something else, typically pre-empting).

Bidding requires space — consider it an auction from 1-35, where each number affects play (and scoring). There’s an argument to bidding “1” say “I have a great hand” like precision does, but then your opponents will typically use their bids to quickly reach the highest safe number possible without worrying that they could have a bonus available. (Your bid has told them they probably can’t). Which may not be that high, but it’s often around 9-13. So precision’s advantage isn’t the big club. It’s when you open something else and get all those negative inferences. When a precision player opens 1 Spade, you often don’t have to worry about whether you can make a slam and bid slowly, you just bid your game. (Sure, you may rarely miss a slam with a perfect fit, but you’ll probably wind up making enough games because the defenders have no information that a revealing auction would have). Also, when a precision player opens one spade, the opponents compete, and then he bids at the three or four level, his partner knows that he’s doing it on offensive strength, not just high card points.

So in some sense, the strength of precision is every time you don’t use the big opening. I’m intrigued by the Polish Club systems, (where 1C shows all the big hands, but also shows the “balanced, barely enough to bid” hand, which puts some uncertainty for the opponents.  If they have a “compete quickly based on shape” system, often they could miss a reasonable game, or sacrifice when the opener can’t make much of anything. Or they could bid reasonably and then discover opener does have a huge hand.

Miles system works the opposite way. The 1 Club is usually moderately big, so the partner of opener will often be able to quickly determine that the opponents have gotten too high, but there’s no shot at slam (or game) and be able to punish them. Opener’s tightly constrained hand (almost all opening bids in this system have a 5 point range, except for the few exceptions on 1C (which are rare) and the 2C/2D bids technically have a 17 point range, but effectively 5 points.  (Only 1.5% of the hands have 20+ HCP, and only 0.02% have 26+)

Anyway, there’s very little discussion online about this system (at least, not that google can see), although I know that sometimes commenter JeffG plays with Marshall Miles (and in fact they were on the same team for the Vanderbilt’s a few weeks ago). The ACBL regulates bidding at tournaments somewhat draconianly (although I understand the reason behind it, it does annoy me), but this system is (apparently) legal. I guess I enjoy tinkering with systems, just like as in other games.

Anyway, in my mind, the unbalanced diamond compares with Precision (since they are both “Big Club” systems) and seems to compare reasonably well. It’s certainly interesting.


Written by taogaming

March 28, 2010 at 5:08 pm

Posted in Bridge

Tagged with

5 Responses

Subscribe to comments with RSS.

  1. How much of bidding system design is probabilistic algorithms, and how much is human judgment.

    For example, I would think that given good bridge software, a database of 1000s of hands/bidding sequences evaluated and rated by humans, and a sophisticated monte carlo process, you could come up with a bidding sequence that was fairly optimized.

    So does a database like this exist and do people test new bidding methods against it, or is it only by feel, experience and empirical testing.


    March 28, 2010 at 9:56 pm

    • Some is probabilistic. Even very good bids work out poorly sometimes. At matchpoints, you can risk insanely bad scores for frequent small improvements. (For example, a bid that switched a -90 to a +110 80% of the time but gave you -1100 the other 20% would be great. But that’s matchpoints, where you care about how many pairs you beat, not the margin of difference).

      A fair amount is judgement, of course. If your bid’s meanings are fudgeable partner won’t know what you have, but there are some auctions where partner has to recognize you are under pressure, and make allowances. And, of course, you can take risks if you judge that your opponents are less likely to punish you. (Just as a mathematically optimal poker play may not be the best play against many opponents, since they are easy to read). And, even if your partner has the hand you expect, the auction may have told you that the cards will be kind/unkind, which may change your bid.

      But to answer your question, computer simulations are used sometimes. Even 18 years ago (when I last had my subscription to Bridge World, before renewing this year), players would use a specific Monte Carlo simulation (called Borel to argue a point. In a recent issue, someone used a deal program to randomly generate hands, then a ‘double dummy’ solver (which finds the theoretical maximum with best play on both sides) to aid in discussion. Now, a double dummy solver sees all four hands, but as an approximation its pretty reasonable (sometimes the solver would find a play no human declarer would, because the play only works against that specific placement of cards, but sometimes it finds a perfect defense for the same reason, so it’s assumed to be a wash, mostly. Probably better than trying to rationally pick the best play for all sides with no bias).

      In fact, I couldn’t sleep last night and spent several hours tossing and turning and thinking about a specific defense against a specific bidding situation, and mentally arguing pros and cons. My initial feel is that my defense works but occurs too infrequently, and that I should run a simulation to determine if that’s true. (A few hours later, still awake, I modified the defense, mooting the point).

      Do most people run simulations? No. But a few do, and the tools are out there.


      March 29, 2010 at 8:45 am

      • My somewhat extensive experience with simulations is that they don’t work well. You can either do them by hand, in which case a couple hundred hands is a fair bit of work, or you can use a double-dummy solver on lots on hands, which isn’t too hard. The results from double-dummy solvers are badly off; hands simply do not play out double-dummy. A couple hundred hands is rarely enough to make a sound judgment.

        There is no “database of 1000s of hands,” but if there were, it wouldn’t be big enough. The number of situations is many orders of magnitude above that, and we’d need thousands to millions of hands per situation.

        So, overall, simulation technology, while not useless, is still in its infancy. Basically, the issue is that simulations either play like bridge software (very badly) or have information not available in real life. So they don’t help when the tradeoff is “should I hide or show this information,” or when the point is to give an opponent a problem. Add in that the energy space of bridge hands is very high frequency (lots of tiny portions of the sample space contribute heavily to the result and are hard to importance sample), and overall you get that simulations only work well in a very small set of cases unless the simulator is willing to do an enormous amount of monkey work.


        March 29, 2010 at 11:54 am

    • Mostly, neither. Bidding systems are mostly tradeoffs. You have a limited amount of space, so you decide how much you are willing to spend on various goals like slam bidding, game bidding, and pushing the opponents around. No one knows what the optimal ratio is, and simulations aren’t good enough to give the answer. Pushing the opponents around means that they are given problems. How well they solve these problems is simply something a simulation cannot do. Yes, you might be able to do it by hand, but we are talking about millions of hands to make good estimates, not thousands.

      So designers use a combination of judgment, experience, and personal prejudice (they tend to pick things they find the most fun—for example, Marshall likes to pass forcing bids, so he builds a system which reduces the downside of passing forcing bids (no, it doesn’t work)).

      Every once in a while, someone comes up with a tweak that is clearly superior to standard without any significant losses. Typically, within a year, most of the top players are using it. But those are more tactical issues than strategic ones, which is what I think you are talking about.

      So the final answer is really “feel, experience, and empirical testing,” though, as with most everything else, empirical testing tends to get short shrift; after a huge amount of time invested in something, giving it up is a hard thing to do.


      March 29, 2010 at 11:45 am

  2. Forget the Unbalanced Diamond. There are a few good ideas in there, but overall the system is so bad that most of Marshall’s partners won’t play it with him. Even some who used to have stopped; it gets lousy results.

    The reason is that the system is designed to stop in part scores. It’s no good at slams, isn’t useful for determining the best game, and it puts very little pressure on the opponents. Those things all score much more than part scores, so the basic design goals of the system are flawed.

    The reason that most systems these days do not use multiple low-level opening bids for strong hands is that there are not enough of them. It’s better to use most of them to attack the opponents. The last successful system with more than one strong opening was Breakthrough. It was played by Katz and Cohen in the early 70s. Like Marshall’s system, they used a strong but limited 1C and a stronger 2C. Bridge was a lot different back then, though, and of course K & C resigned from the ACBL under a cloud of suspicion, so tri-level opening systems haven’t seen much popularity since.


    March 29, 2010 at 11:32 am

Comments are closed.

%d bloggers like this: