[AyunuS]

I've noticed a lot of the time, even with a huge overbid, GIB doesn't double. Once I bid 7 clubs and LHO GIB had 5 clubs including the Q and still didn't double. It seems to me that GIB thinks you never make sacrifice bid or something like that, but rather you bid just how it does. Here's a hand which, in my book, is essentially an automatic double. http://tinyurl.com/879ftcs Notice west has trump AK, and a singleton club A. And he gets to go first. Thus, barring a really unlikely void in clubs by any player on my team, he can be guaranteed to set the contract, even if his partner has a very bad defensive hand. Then, on every single other table, they made 4S to get more points than they got on my table so I got 100% MPs. Since I know it rarely seems to double in cases like this, and that it usually only bids stuff it's going to make, then it's to my advantage to bid 5H as we get a better score than letting them get 4S even if we go down by 4. I know this was a rare case where my team's bidding was just awful, but still, GIB is often too easy to sacrifice against IMO.

[barmar]

It's hard to write explicit rules for penalty doubles, so we generally rely on simulations. But in this case, the software reports that it can't generate a decent sample of hands for the simulations. You and I can see that it doesn't really matter what's in the other hands, 5♥ is obviously going down. But GIB has only its rules and simulations to base its decisions on.

We can obviously add rules to handle the simple cases like this one, but fixing the general problem is harder.