Wednesday, December 30, 2009

All the matchpoints

It’s rare for 100% of the matchpoints to be at stake on any decision. Look what happened on this hand. In a robot duplicate I held AJ98 7 A73 KJ532 and opened 1C. It continued 1H by lho, X by partner, up to me. I think this is an obvious 2S bid. 1S is a nothing bid that could be on 3 trumps with no H stopper, so to me 2S shows only something like 14-16 support points, which I have easily. The field disagreed unanimously: 24 of 24 bid 1S! So, when North bid 4S, I was unknowingly in a top or bottom situation, looking at:

North: KQ54 QJT Q6 T764

South: AJ98 7 A73 KJ532

West cashed a heart and led the ST. I played SJ, S8 and he pitched a heart. I opted to overtake and lead a club (I must note I erred by leading the 4 rather than a higher spot, although this turned out not to matter. Never waste your smallest spot from the short hand!) RHO hopped CA to lead a heart; I correctly pitched a diamond and lefty won and played a 3rd heart, RHO ruffing. Now a simple matter to overruff, pull trumps and guess clubs, playing LHO for Qx (which he held) since he would lead a stiff, for making 4 and all the matchpoints. Almost...

See, I use the keyboard input on bbo, which works fine; no typos for some time now. When following, you just hit the rank; when not, suit then rank. *But* if you just hit a rank, it assumes the last suit you played if possible. You see where this is going? By just hitting A, I “overruffed” with the DA instead of the SA! That was down 2, and exactly 0% of the matchpoints. You can see all the results at

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.