[pilowsky]

What is an opening hand for GIB?

Bridge players are opening on lower and lower hand strengths, but the hand strength that GIB opens with can still be a bit mystifying.
The BBO convention card does not stipulate an opening HCP range for an opening hand in for suits; only expected minimum lengths.
It does stipulate a range for two-level openings. 5-11 for D,H,S and 22+ or 9+ tricks for C's.

By inference then, one might expect that GIB would regard 12+ as an opening hand.
It turns out that the method that GIB uses to assess the quality of an opening hand is a bit more subtle than A=4, K=3 etc.
I suspect that something akin to the KR calculator was incorporated into the GIB simulator.
I think this is because GIB does not always open on 12 at the 1 level, It sometimes opens with 11 at the 1 level, and I have also seen it pass hands that some of us would open at the two-level.

To test this idea a little more rigorously, I generated two sets of hands where the North robot was the dealer and either had 11 or 12 HCP. The shape and the rest of the HCP were distributed randomly.
I acknowledge in advance that the sample size is small (16 in each set). On the other hand, it is not so small that some interesting results did not emerge.
Each set of hands was given to four robots to play at a teaching table while I watched and recorded (hands were generated by Playbridge. The only stipulation was that North must have 12 and only 12 or 11 and only 11 HCP.
In the first set, North opened every hand it was dealt (16/16). NS ended up as Declarer in 8/16 contracts.
I will not comment on whether or not they were the 'best contracts' or the quality of the play, since nobody else played them, and who am I to judge the play. Still, it is interesting to note that in this group, the Declarer made or exceeded their contract 13/16 times.

In the second set of Hands, North always has 11HCP.
This time, North still opened the bidding 6/16 times.
The reason; shapely hands:

6331;3NTS+1,
5521 ; 4CE+1,
5431; 6CW=,
8221; 4CN+2
5440;5CE.

Finally, I generated 16 hands where North had 10HCP. North passed all of them. Given that there were only 16 hands, and 79.5% of hands do not have a 6 card suit - and the 6 card suit must not be Clubs - this does not seem unusual.
From all of this, I would conclude that GIB never opens with less than 11. It will frequently open with a shapely 11, and will almost invariably open with 12.
As with Stayman, GIB seems to be using something more than is revealed in the system notes or on the card to calculate the value of its hand.

[nullve]

pilowsky, on 2020-August-09, 03:08, said:

From all of this, I would conclude that GIB never opens with less than 11.

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[pilowsky]

So they do. https://tinyurl.com/y3ursenj.
Fra nu af skal jeg krydse vejen uden at se begge veje.
But they draw the line at 9
https://tinyurl.com/y6qsymn6