[thorvald]

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The explanation to 4N is "Pick your better minor"

[smerriman]

Amusingly, 10 year old GIB would make exactly the same 4NT bid.. but its partner would *always* pass, even without the double. It had no followups programmed at all, and thought that 5♣ or 5♦ (by West, or even by East if doubled and passed back) showed enough combined strength for game.

In one of the last GIB updates in 2018 they fixed some other sequences involving 4NT bids (like unusual 2NT followed by 4NT) which GIB would also always pass. My guess is they added in a rule for 4N P ?, and forgot about 4N X ?.

[thorvald]

I have just tried to recreate the bidding, but here East passes over 4♥, so I will assume it is only for advanced robots

[smerriman]

Yes, advanced robots only both pass and 4N when simulating and choose between those two options. But over 4N and without the double, West does bid clubs, so that part did get fixed. Just not the equivalent with a double.

[cherdano]

It's almost as is the whole idea of fixing common GIB bidding problems one auction at the time is doomed to fail.

There used to be millions of auctions where GIB thought bidding game in competition shows a monster. After lots of hard work by the BBO GIB team, there are now 30% less of them. Congratulations.

[smerriman]

It depends what you mean by fail. If succeeding is never having silly definitions for bids, certainly there is no hope..

But if a particular bug occurs time and again when playing with the robots, and gets reported numerous times on the forum, and then suddenly it's fixed.. that increases the enjoyment of playing with the bots immensely.

Failing is not even getting a response 6 years after reporting a problem.