[qetzel]

Hi

I'm playing against 3 robots and not always understanding their bidding. IN the hand below:



Why would the East robot not bid 3 or 4 hearts in response to the initial West robot 3 diamond bid?

[shyams]

In my view, East's pass is a fair action. There are numerous things fortunately right here which allows 4♥ to make.

West could have had a club loser; South could have had ♥AJx; if West doesn't have the ♠Q, you'd likely lose 2 spade tricks; the diamond finesse could be wrong; West could have 0-1 heart cards.... etc

If I were seated West, I would not worry about missing a heart game because (a human) partner did not bid his long suit.

[thepossum]

I know my basic sims mean nothing but 3D does come out ahead of hearts
Note it was very basic and didn't add up all possible points outcomes and try to guess what other hands have and what shape other suits were or anything
It is a tempting hand to bid though
I prefer to make decisions not after seeing all 4 hands

[P_Marlowe]

4H is a reasonable contract due to the meshing spade honors.

If East bids 4H, this has to show a suit, that is playable oppossite a single,
and I would not call the suit East happens to hold as sufficient to send this
message, you may disagree.

Bidding 3H is ok, ..., if you hit West with hearts, he may raise, and you dont
mind a 4D bid, given that you have 2-3 tricks for a diamond contract, and the game
bonus is worth a shot. This is human know how / logic applied for a specific pair
of hands.

General rules, and my guess is, GIB uses rule instead of simulation for bidding,
tell 3D is sensible contract, game strength is not likely, the partnership has
at most 22HCP, and it may well be less than 20.
This is robots logic, developed 20+ years ago, my take is GIB (and the framework) was
developed before 2000, but I may be wrong. You can adapt the rules, but adaption
has its limits.

[thepossum]

The big uncertainty for me is the soundness of West's pre-empts - from experience the bot has very sounds pre-empts
- and upping the soundness of the pre-empt makes hearts decent shot
But if the East bot does run sims and uses the theoretical points range pass was ok

[smerriman]

While the robots make a lot of odd bids, this isn't one of them.

GIB plays sound preempts vulnerable; they're certain to have two of the top three diamond honors, and 6-9 HCP total. West is likely to hold a heart singleton, so even if we give them one of the best looking hands - Ace of spades and KQ of diamonds - we're going to have two trump losers, a diamond loser, and a club loser - you're certainly not expecting a club singleton!

As shyams mentioned, they needed a lot of things going their way in order for 4♥ to make - indeed, it only makes on 20% of the possible hands West would preempt with, so it would be a big mistake to bid 4♥.

3♥ may seem reasonable at first glance, though don't forget this is a forcing bid, so you won't be playing there. West will raise to 4♥ with 2 card support, otherwise revert back to 4♦.

If West has 2+ card support, the chance of 4♥ definitely increases.. but doing a computer simulation, that's only around 42% of the time. If that support were a given, those odds may be just large enough to make it worth bidding vulnerable at IMPs. But it's not a given - that 2-card support only happens around a third of the time, and the other two thirds we're a whole level higher in diamonds and in some trouble - there's a 69% chance we're going down in 4♦ (and more than half of those occasions, we were going to be making 3♦).

When you average all of those combinations out, passing works out about 1 IMP/hand better than bidding 3♥, which is a pretty significant margin (and miles ahead at MPs, of course).

Of course, a human wouldn't be doing any of those percentage calculations at the table but the more you start to consider what possible hands West may hold, the more you'll see game is pretty low odds - so best to pass and take a plus score if you can get one.