Double Dummy Usefulness

I was going to write another long post analysing in detail how useful double-dummy analysis is, but I don't feel it's necessary. For one, it's mostly just about using common sense and experience — you get a feel for what kind of results are useful and what aren't — but also pretty much every simulation we do will involve some degree of assessment so the same topics will come up in future blog posts.

Also, I'm getting bored of this introduction to simulations and want to get on to more interesting things!

I will, though, give you some random bits of crap to use as manure for your thoughts to grow.

• A DD engine declares perfectly, but also defends perfectly. In a lot of hands the two cancel each other out.
• Higher level contracts are usually more accurate than low level contracts. There are less points of decision for either side in a typical 7NT contract than in 1NT and the less decisions that need to be made by a stupid human, the closer to 'perfection' they will get!
• Balanced distributions tend to be more accurate than wild ones. This is because with a wild distribution a lot of tricks will often hinge on one decision which, for a human, is just a guess. In a balanced no-trump contract, the cost of not making a double-dummy decision isn't so severe and you can often get it back. The perfect example is leading against a Gambling 3NT opening. Which Kxxx major suit do you lead from when one will lead to six off and the other will lead to plus three?
• Hands with holdings like AQ10 or KJx will be over-valued as the double dummy engine will always get any guess right. Therefore, you should be mindful when fixing hands with tenaces like this.
• In most cases, when you're comparing two strategies, the strategy that comes out best with double-dummy analysis will also come out best if you use single-dummy. Thus you can decide whether you prefer to play in 3NT or 4 on our example deal based purely on which one comes out top.
• If you're scoring with IMPs or aggregate points, you don't really care if the contract makes one overtrick or two, so any error between DD and SD will be marginalised.
• You're sitting in the pub after a session of bridge and looking at the Deep Finesse analysis. How often do you think to yourself that the number of tricks is completely unrealistic? Occasionally you'll notice it dropping singleton Kings or leading unsupported Aces to give partner a ruff, but for the most part you say: "Hmm, DF says it can make 9 tricks. Yep, 3NT should have made — sorry partner!"
• What is single dummy anyway? The difference between club level play and Bermuda Bowl level play is quite a few tricks! Just treat Deep Finesse as the epitome of expert play.

That is all.