[goffster]

http://tinyurl.com/jnt6mj7

4S seems automatic given a pure 4 loser hand.

[Stefan_O]

goffster, on 2016-April-24, 21:10, said:

http://tinyurl.com/jnt6mj7

4S seems automatic given a pure 4 loser hand.

I agree.
just wondering how weak 3S actually is here... I see no description of bids in the diagram...

[Bbradley62]

GIB doesn't evaluate hands that way. South thinks he has a hand worth 17 total points* opposite a preemptive raise, so he doesn't think game is a good prospect and there's no need to sacrifice vulnerable when opponents aren't in game.

* 15 HCP + 2 for shortness (1 in ♦ and 1 in ♣). Whenever GIB has both shortness and HCP in a suit, he discounts the total points by 1. (The fact that I explain this is in no way an endorsement of the methodology.)

[1eyedjack]

I was thinking about this a few hours ago when I was supposed to be on the clock writing a spreadsheet.

There are (at least) two approaches that GIB could take to hand evaluation in cases like this:

Approach 1:

Each hand forms an evaluation of its playing strength, by some formulaic approach. HCP + distribution + fitting cover cards etc etc. Then it compares the combined announced values with some database of expected number of tricks, and on that basis accepts an invitation or declines.

Approach 2:

As approach 1 except that once one GIB makes a non-forcing bid, the other GIB resorts to simulations (taking into account partner GIB's announced formulaic valuation of its, that is partner's, hand), and on the basis of that simulation run decides whether to accept the invitation.

A human pairing, particularly of modest experience, tends to adopt approach 1. An expert human pairing would probably apply a combination of both approaches. Initially the final bidder may apply a formulaic approach (maybe several), and then maybe picture a few sample hands that partner could hold. But we are not interested in human pairings here.

The point on this hand is that while GIB has a method of evaluating hand strength, for the purposes of communicating said strength to partner as a consultative measure, I would not expect South over 4D to be using a formulaic approach to its evaluation (effectively alternative 1 above). All the consulting has been completed. It is time to choose a final spot. Time for sims. I would expect that process to come down on the side of bidding 4S

[Stefan_O]

1eyedjack, on 2016-April-25, 15:28, said:

As approach 1 except that once one GIB makes a non-forcing bid, the other GIB resorts to simulations (taking into account partner GIB's announced formulaic valuation of its, that is partner's, hand), and on the basis of that simulation run decides whether to accept the invitation.

Well, what I have understood, that is just how Gib is supposed to work.
At least it was, long time ago when Matt Ginsberg quit the development.
After that, we really dont have much info re. what has been done to the code-base -- or do we?

[Stefan_O]

Actually found some info here:

https://www.bridgeba...escriptions.php

See the bottom section, "Why doesn't the robot's hand always match the description?"

[lycier]

goffster, on 2016-April-24, 21:10, said:

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4S seems automatic given a pure 4 loser hand.

Stefan_O, on 2016-April-25, 01:47, said:

I agree.
just wondering how weak 3S actually is here... I see no description of bids in the diagram...

Hi Stefan_O :

I definitely disagree with your opinion above.
This is a classic hand which shows how correctly Gib evalues !!!
- Why would you think Gib should bid into 4♠?
Assume you are a declarer, would you have ability to get 10 tricks on 4♠ contract?
Never.
To be honest, Gib evaluation is very good, its judgement is really excellent, really better than many people in this hand, especially including goffster and Stefan_O, I will give you some evidences here.
In fact , singleton ♣Ace is a kind of devaluation, only about 3hcp, so normally this hand only have 14 value points, and the worse is south Gib holds five cards ♥ !
Facing to 4♦, if south Gib overbid 4♠, it would get negative points, if pass and insist on defense, it eventually get positive points.
Would you think it is just a exact reason for south Gib to bid up to 4♠?
- After 2♣, how many differences are there between north bidding 2♠ and jump 3♠?

Today I checked and replayed this hand :

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Result : 3♠S+1

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Result : 3♠S=

How wonderful Gib plays !!!

Any ideas?

[1eyedjack]

lycier, on 2016-April-30, 07:24, said:

- Why would you think Gib should bid into 4♠?
Assume you are a declarer, would you have ability to get 10 tricks on 4♠ contract?
Never.

If you have the benefit of seeing the E/W hands before committing (or not) to 4S, then you would stop in 3, because you would be aware, however unlikely at single dummy, of the adverse Heart ruff.

Just with the benefit of seeing the N/S cards, of course you should be in 4S, no question.

Given the limitation on the method of hand evaluation employed by GIB, which utterly fails to appreciate the power of the South hand, then within that constraint GIB possibly uses its evaluation system reasonably. The complaint in this thread is that the evaluation methodology used is woefully inadequate. That is IF, of course, it is using that methodology in deciding to bid 4 at all, rather than simulations, which I would have expected, and which would have brought to light the power of South's hand.

lycier, on 2016-April-30, 07:24, said:

How wonderful Gib plays !!!

Any ideas?

You think that the Club Jack by East on the first hand is "wonderful" play? It may be right on the available information, but it certainly was not successful here. Ducking the King of Diamonds on the second hand is probably not the greatest declarer play, providing the opportunity to switch to Hearts earlier. Maybe that is more indicative of a Heart continuation? Not sure.

[lycier]

1eyedjack, on 2016-April-30, 09:16, said:

If you have the benefit of seeing the E/W hands before committing (or not) to 4S, then you would stop in 3, because you would be aware, however unlikely at single dummy, of the adverse Heart ruff.

Just with the benefit of seeing the N/S cards, of course you should be in 4S, no question.

Given the limitation on the method of hand evaluation employed by GIB, which utterly fails to appreciate the power of the South hand, then within that constraint GIB possibly uses its evaluation system reasonably. The complaint in this thread is that the evaluation methodology used is woefully inadequate. That is IF, of course, it is using that methodology in deciding to bid 4 at all, rather than simulations, which I would have expected, and which would have brought to light the power of South's hand.


You think that the Club Jack by East on the first hand is "wonderful" play? It may be right on the available information, but it certainly was not successful here. Ducking the King of Diamonds on the second hand is probably not the greatest declarer play, providing the opportunity to switch to Hearts earlier. Maybe that is more indicative of a Heart continuation? Not sure.

I am pretty glad to view your reply.
Here I have to tell you the fact you've made a fundamental mistake.
1- South hand isn't so strong than you image. not enough to bid up to 4♠ :
- when with no interference, if facing to responding 2♠, it seems likely the south player have some good reasons to bid up to game.
- when with intererence,it becomes complicated, that's to say it needs the exchange of information to invite game.

On the competitive sequences,after 2♣,
- 2♠ of south player says " 3-card+ ♠,6-11 TPs ".
- 3♠ of south player says " 4-card+ ♠,4-8 TPs ". Here we should add a sentence, that's " usually with unbalanced hand".
In fact, preemptive jump 3♠ shows weaker in hcp but better in shape point.
Generally speaking, usually south should refuse the invitation.

2- The bridge is a matter of partnership,this is a classic hand in which test real skill of player - how to handle with such kind of problems in the following sequences will be a great to player's skill.

3- Even facing to partner's raise, south should should have common sense to judge this is a hand with devaluation.

Note defense is usually the best offense in this situation.

Whether ducking or not, east always know west is sure to hold singleton in ♥ due to doubleton ♥ in the dummy, actually declarer impossiblly get 10 tricks, whatever you play carefully.
Are you going to want to build on the beach?
In a word, this hand is a common sense for intermediate players.

[lycier]

As a Gib fans, I have to say again :
How wonderful Gib plays !
Hats off to BBO Gib programers !