[thorvald]

---

Without the Double of 3♦ West would bid 4♣, but now the bots stopped in 3♦X with 7 tricks instead of making 10 tricks in a ♣-contract

[helene_t]

Yes, there a some obvious contract improvements which GIB misses. Presumably, biddiing 4♣ over the double is a free bid and therefore shows some values?

[pescetom]

thorvald, on 2022-August-18, 06:24, said:

Without the Double of 3♦ West would bid 4♣, but now the bots stopped in 3♦X with 7 tricks instead of making 10 tricks in a ♣-contract

I'm more puzzled about the esoteric double of 3♦ (is the description precise/logical?) and why on earth NS do not reach 4♠

[smerriman]

pescetom, on 2022-August-18, 14:31, said:

.. and why on earth NS do not reach 4♠

I think this is the key problem here. When I simulate this, West does bid 4♣ most of the time, though sometimes decides to pass. But in all of the simulations, it's extrapolating a lot of opponent continuations to determine the final outcome.

Eg, in the simulation where it came up with pass winning, most of the simulated deals ended with a contract of 4♠ whether you pass OR bid 4♣, because GIB hates passing penalty doubles and it's relying on this when completing the auction. While it did see the double being passed a couple of times for bad scores, it also thought that sometimes passing put the opponents in 3♠, while bidding 4♣ either was going down several tricks, or pushed them into a making spade game..

In one of the deals it even found a bug in the early version of the database (doesn't exist now though), thinking one opponent would cue 4♦ and the other pass it :/