Something is wrong here

[thorvald]

[hv=url=https://www.bridgebase.com/tools/handviewer.html?bbo=y&lin=pn%7CHuman%2CRobot%2CRobot%2CRobot%7Cst%7C%7Cmd%7C4SAQJ2HK975DJ965CA%2CST843H64DT74CQ976%2CSK9765HJT83DA8CT5%2CSHAQ2DKQ32CKJ8432%7Csv%7CE%7Cah%7CBoard%206%7Cmb%7C1C%7Can%7CMinor%20suit%20opening%20--%203%2B%20%21C%3B%2011-21%20HCP%3B%2012-22%20total%20points%7Cmb%7CD%7Can%7CTakeout%20double%20--%202-%20%21C%3B%203-5%20%21D%3B%203-4%20%21H%3B%203-4%20%21S%3B%2012%2B%20total%20points%7Cmb%7CP%7Cmb%7C2S%7Can%7CJump%20new%20suit%20--%204%2B%20%21S%3B%209-12%20total%20points%7Cmb%7C3D%7Can%7C5%2B%20%21C%3B%204%2B%20%21D%3B%2021-%20HCP%3B%2016-22%20total%20points%7Cmb%7CD%7Can%7C2-%20%21C%3B%205-%20%21D%3B%203-4%20%21H%3B%203-4%20%21S%3B%2014%2B%20HCP%3B%20biddable%20%21D%7Cmb%7CP%7Cmb%7CP%7Cmb%7CP%7Cpc%7CSA%7Cpc%7CS8%7Cpc%7CS9%7Cpc%7CC3%7Cpc%7CSQ%7Cpc%7CS3%7Cpc%7CS5%7Cpc%7CC8%7Cpc%7CSJ%7Cpc%7CS4%7Cpc%7CS7%7Cpc%7CD2%7Cpc%7CC4%7Cpc%7CCA%7Cpc%7CC9%7Cpc%7CC5%7Cpc%7CS2%7Cpc%7CST%7Cpc%7CSK%7Cpc%7CD3%7Cpc%7CDK%7Cpc%7CD6%7Cpc%7CD7%7Cpc%7CDA%7Cpc%7CD8%7Cpc%7CDQ%7Cpc%7CD5%7Cpc%7CD4%7Cpc%7CC2%7Cpc%7CH5%7Cpc%7CCQ%7Cpc%7CCT%7Cpc%7CDT%7Cpc%7CH8%7Cpc%7CH2%7Cpc%7CDJ%7Cpc%7CH7%7Cpc%7CH6%7Cpc%7CHT%7Cpc%7CHQ%7Cpc%7CCK%7Cpc%7CD9%7Cpc%7CC6%7Cpc%7CH3%7Cpc%7CH9%7Cpc%7CH4%7Cpc%7CHJ%7Cpc%7CHA%7Cpc%7CCJ%7Cpc%7CHK%7Cpc%7CC7%7Cpc%7CS6%7C]399|300[/hv]

 

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]

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♠ :blink:

[smerriman]

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

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 :/