Saturday, December 26, 2009

Robot Statistics

Most of you are BBO users, and probably know of the robot duplicate tournaments that were introduced earlier this year. You play against three robots (the program GiB, on one of its faster, less skillful settings) and your scores are matchpointed against other humans playing the same hands. You always get the most hcp at the table. The attraction of this format is that you have many more key decisions per hour than you do in a normal human game; you wind up declaring about 55% of the hands, and the hands go by pretty fast. As a result some people I know are total addicts…I’m a very mild but steady addict, playing 3-4 12-board sessions each week. Of course, the context of some decisions is very different from real bridge, where you wouldn’t (I hope) follow the rule of “never count on partner’s judgment.” You can read a long series of articles on Glen Ashton’s blog and some on Memphis Mojo’s. As far as tactics, I basically open a 14-18 notrump (a bit liberal on distribution) and 19-21 2NT. This is not only to hog the hand, but also because partner’s bidding is not quite as bad as in other auctions.

Partly because it is rare to have useful statistics on individuals in bridge, I got curious about breaking down my results and those of others. Bridgebase will give you a file with a month’s worth of results, and I wrote a parser to break these down by who declared. I might compile more statistics at some point. Here’s what my program outputs now, from being fed the last 3 months of my results (SD=standard deviation):


North declared 105 hands(24.36%): NS averaged 55.22%, SD = 23.15
East declared 41 hands(9.51%): NS averaged 53.77%, SD = 28.04
South declared 243 hands(56.38%): NS averaged 60.55%, SD = 26.31
West declared 37 hands(8.58%): NS averaged 61.80%, SD = 27.91
Pass declared 5 hands(1.16%): NS averaged 50.81%, SD = 10.13
Total of 431 deals, Average: 58.60% SD: 25.93
(Statistics exclude 1 average minuses.)

Comments: It’s not surprising I average better as declarer than as dummy. This doesn’t necessarily mean I should hog it even more – on a hand where I artificially made myself declarer by putting it in an inferior contract, my average would certainly be less than the 60.55% above. In fact, I’m quite satisfied with averaging 55% as dummy – this is a rare instance where we can say for sure that any advantage over the field represents solely bidding judgment! Good players who I’ve looked at tend to average 53-55% as dummy – this partly represents bidding to the right level, and partly that the field sometimes takes hand-hogging to excess. Finally, note that the swingiest hands are when I defend. The field doesn’t like to pass, so defending leads to some tops and bottoms. I defend a few percent more hands than most people I’ve looked at. (One reason is I avoid marginal takeout doubles, fearing partner’s insanity.) The results are acceptable, with a mp average on defense only about 1% less than my overall.

The highest MP average I’ve come across is Mark Lair’s. This could surprise you only if you didn’t know he plays the GiBs quite regularly. Here are his stats for a 2-month period:


North declared 558 hands(30.56%): NS averaged 55.07%, SD = 23.15
East declared 132 hands(7.23%): NS averaged 57.14%, SD = 25.97
South declared 1009 hands(55.26%): NS averaged 62.42%, SD = 24.68
West declared 120 hands(6.57%): NS averaged 55.20%, SD = 27.18
Pass declared 7 hands(0.38%): NS averaged 62.69%, SD = 16.47
Total of 1826 deals, Average: 59.32% SD: 24.72
(Statistics exclude 72 average minuses.)

I can certainly live with being just 0.7% worse than Mark Lair, at this odd but entertaining form of the game.

Monday, November 16, 2009

A better line for today's NYT hand

Many of you are probably regular readers of Phillip Alder's fine column in the New York Times. It's hard to say that someone misplayed when they executed a successful compound squeeze, but I think that is true in today's hand. First look at http://www.nytimes.com/2009/11/16/crosswords/bridge/16card.html?_r=1&ref=arts and see what you think. Then, here is the message I sent to Alder:

Hi Phillip,

It appears that once West pitched a club on the 3rd trump and then turned up with 4 spades, a simple 100% line was available. If declarer, after 3 trumps and 2 spades, just played CA, CK, club ruff, then if West guards clubs there is a simple squeeze (cash last trump then hearts) and if East guards clubs a standard double squeeze with hearts the common suit. In practice, of course, clubs would simply split. The club pitch is vital to this being 100%; it means declarer will always know who guards the last club. Note that Bertheau’s compound squeeze line is not 100%, as declarer can guess wrong as to which suit West has unguarded.

Therefore, the club pitch by West is an error, although understandable since declarer’s hand was completely unknown. To avoid giving declarer a sure-thing line, West must first pitch a heart. A club pitch on the 4th trump would be OK, since any pitch by declarer weakens his hand in a way that kills some variant of my 100% line.

Jonathan

Sunday, November 15, 2009

Establish your tricks -- lead trumps!

When balancing or competing against the opponents' 2S, one thing you fear is that your side has 3 7-card fits to choose from at the 3-level -- usually not a fun choice. But sometimes the opponents let you off the hook.

North: KTxx QJxx xx AKx
West: xxx AKx xxx Q9xx East: Ax xxxx AKxx Jxx
South: QJxx Tx QJxx Txx

At neither vul in a close sectional KO final, North opened 1C and raised partner's 1S to 2S, and East (Marty Harris) entered with a double. I guess (?) that most good players would favor this action at these colors, even though it is far from safe. I (West) bid a scrambling 2NT, preferring this to 3C in case partner is 2=4=5=2 or the like -- I also see a case for 3C, putting the ruffs in the short hand if (as here) we have a choice of 4-3 fits. Seemingly we were headed for -100 in 3D, but North came to the rescue with a 3S bid -- he had told his story sufficiently already, don't you think?

So, my lead against 3S. It seemed unlikely hearts were going anywhere, so I avoided the AK lead and tried a trump. This was a success when Marty won and found the club shift. Now it was routine to take 6 tricks for +100, and win 5 when our teammates played 2S for +110 on the HA lead. It's cute that we must avoid touching either of our AK holdings to get all our tricks, and that my trump lead allows a succesful active defense while the HA blows a tempo! My satisfaction with this is far out of proportion to the 1 extra imp it gained.

Alas, this hand was not enough, and we lost the match by 6.

Wednesday, November 4, 2009

Follow-up to lead problems

1. I didn't find it at the table, but on later consideration I think DA as Pretender suggests is clearly the best shot, trying for a simple path to 4 tricks. It does clear up a guess when partner has Jxx, but so be it. This was the winning lead at the table. Even though declarer had only 3 diamonds (6=3=3=1) and can pitch the third, your trumps are promotable when partner turns up with Jx and the HA.

2. I led the CQ, and clubs were the only losing lead. I still think maybe it was normal, but perhaps there is a good reason to make a different guess. Mojo, why is a heart so obvious?

Monday, October 26, 2009

Decisive opening leads from Sunday

I hope some loyal readers have their alerts set to find out there is an actual post! I'm busier with work this year, so the blog has slowed way down. I did make it to a regional in Lake Geneva, WI this weekend. Here are two critical opening lead problems from yesterday's Swiss:

1. You hold AT Jxxx Ax QTxxx, and the opponents bid uncontested, P-1S-2C!-2D-3D-4S, where 2C was defined as 3-or-4-card Drury, and 2D as natural. What do you lead against 4S?

2. You hold xxx QTx 9x QJxxx, and they bid uncontested 4S-4NT-5H-6S. Your lead against 6S?

Saturday, September 12, 2009

Defensive problem from BB final

You're up about 80 with 42 boards to go in the Bermuda Bowl final, and your opponents aren't shy to begin with, so you'll be given some defensive opportunities. Here's a chance to pad your lead...or make things a little more interesting:

You: T7 K32 QT73 AK84 Dummy: A984 T876 A J653

You deal at both vul., and it goes 1D-P-1H-1S-X-3D-X-P-P-4S-AP. I'm pretty sure 3D was a 4-card limit raise and passing 3D-X showed interest.

You lead the CA (agree?) and get the CT from partner, right-side-up. Your move?

Tuesday, September 8, 2009

Play problem from Monday's Swiss

The obvious 1nt-3nt auction gets you to a contract that is tenuous, to say the least:

Dummy: 94 Q94 AK764 T92
Declarer: Q763 AJ83 J53 AK

West leads the C4. Plan the play (at imps).