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The Robot can't defend (example 1)

#1 User is offline   1175 

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Posted 2024-May-25, 21:19

Hi,

First post here. I have registered for an account to write about this issue (and I suspect I will use it mostly to complain about the Robot :) ).

After playing for a couple of months (around 2000 hands) in the duplicate IMPs (where I basically live for now), I feel ready to start assigning grades to the Robot. For defense, it deserves a "D" (at best). Where do I begin? It often leads too passively against NT (I recall numerous cases where the "obvious" lead beats the contract, but the Robot led declarer's suit). The Robot often doesn't lead the suit that its partner bid (aggravating when I have made a questionable bid just to get a specific lead). The Robot seems particularly poor at giving partner ruffs (I recall one hand where the Robot had three chances to give its partner a ruff, but never did). It often plays higher cards than necessary, which ends up costing tricks for the defense. And as explained in the system notes, the Robot doesn't signal, which makes figuring out the best defense much more difficult for me.

Finally, the Robot often ducks when it shouldn't, and I have an incredible example of that.



At three tables, South rebid 3D over 2H, and played it there (making nine or ten tricks). At one table, South took a preference to 2S after 2H by North, which made eight tricks. At one table, South jumped directly to 3NT in response to the 1S overcall by North - certainly questionable, but the robot at that table led the HJ (oops!). At ten tables, after 2H by North, South bid either 2NT (seven times, which the Robot raised to game) or 3NT (three times). At those ten tables (3NT by South), West cashed four spades and the CA to beat the contract by a trick. I wanted to cater to six spades and four hearts by North, so I bid 3C at my second turn (as shown), which North converted to 3NT. East led the CJ, and West, looking at the cards to set the contract in his own hand (again, four spades and the CA, but in this case, with the South hand exposed as dummy), ducked to North's king, and I quickly scampered home with ten tricks (+10.9 IMPs).

I know that (as a recent arrival) I have much to catch up on (including past posts in this forum), but I have already seen a number fairly bizarre things happen playing with the robots, some of which I will write about in the future. I will try to filter those by asking "would a low-level intermediate player make this mistake?", and in this case, the answer seems clearly "no" (or at least, not more than once :) ).
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#2 User is offline   smerriman 

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Posted 2024-May-26, 02:48

Firstly, be warned - the last time BBO updated GIB was February 2019, so everybody here has lost all hope of GIB being improved. This may have changed recently, as a new member of the BBO team has said they're picking GIB back up, in January that one bug I mentioned would be fixed in "the next version" and as of last month that next version might be out "soon". But BBO have a proven track record of saying things then disappearing forever and hoping you didn't notice, so I won't believe that until I see it.

So most of my replies are less of "yes, that should be fixed" and more "here's my understanding of why it broke".

Many of your preliminary points are part and parcel of the fact that most of GIB's logic is based on double dummy analysis of simulated hands. It will lead passively, because this is least likely to cost a trick, and it "knows" that it will be able to defend perfectly from that point onwards (and also that declarer will never misguess). If you bid a suit, it will adjust its simulations to make sure you have the length but that will still regularly come up as a suboptimal lead double dummy. In reality, much of this logic isn't really valid - a lead that's best double dummy often isn't actually best since partner won't know what the killing return is, while they'd have more information if you played more human leads. But double dummy robots tend to perform better than ones which blindly follow rules like "always lead partner's suit" or "always lead 4th highest from your longest / strongest suit", so this is something you generally have to put up with.

As for your specific example.. I can't be 100% conclusive, but I am fairly certain I know why it ducked, and it's really silly.

GIB, for a bizarre reason, has been told that the standard lead from JT8x is fourth highest, not the J (but J is correct from a suit headed KJTx).

West's logic is that if East has led from a 4+ card suit, it must be headed KJT, and thus ducking is clearly correct. If East has lead from a 2 or 3 card suit, then North with their 9 major cards has at most a singleton diamond, and the diamond suit isn't running, so it doesn't cost to duck.

I hear you say.. wait.. but East *did* lead the J. Yes, after it runs a double dummy simulation, it gives a bonus to the 'normal' lead.. but the gain of breaking its own rules and leading the J was greater.

Robots try their hardest to assume other robots (and humans) haven't broken the rules even though they can, and that's where GIB's biggest errors come from.

But I also hear you say.. wouldn't those cases meant that North had broken the rules by bidding 3NT without a club stopper? Yeah, sure. But the whole auction is broken; 3 is described as natural with biddable clubs!? And 3NT is described as extra values (15-17) and a "partial stop in clubs".. that point range is completely impossible to begin with. But anyway, it trusts inferences from its partner more that it trusts the opposition's bidding.

(Actually, testing this in an older version of GIB, it does play the Ace.. while the bulk of the initial sample was indeed leads from KJTx+, it then includes some non-matching hands in the simulation, and these were enough to outweigh it. But no doubt the basic version of GIB here didn't have a sufficiently large number).
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#3 User is offline   1175 

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Posted 2024-May-26, 06:52

First of all, thank you for your reply (and explanations). I have a few comments (and a couple of questions).

 smerriman, on 2024-May-26, 02:48, said:

But double dummy robots tend to perform better than ones which blindly follow rules like "always lead partner's suit" or "always lead 4th highest from your longest / strongest suit", so this is something you generally have to put up with.


Bridge represents the ultimate game of imperfect information. Good players don't blindly follow rules, but usually don't break them without a good reason.

 smerriman, on 2024-May-26, 02:48, said:

GIB, for a bizarre reason, has been told that the standard lead from JT8x is fourth highest, not the J (but J is correct from a suit headed KJTx).


UGH!

 smerriman, on 2024-May-26, 02:48, said:

West's logic is that if East has led from a 4+ card suit, it must be headed KJT, and thus ducking is clearly correct. If East
has lead from a 2 or 3 card suit, then North with their 9 major cards has at most a singleton diamond, and the diamond suit isn't running, so it doesn't cost to duck.


But shouldn't the Robot take into consideration that his partner might have led from JT8x? If East would absolutely never do that, then ducking makes some (a small amount) of sense. While I appreciate your comment about not trusting opposition bidding (I have seen humans make some, let me say "strange" bids in the duplicate IMPs, that work out incredibly well a surprising percentage of the time), I think that in this case, East doesn't have "room" for the CK (I would at least trust the opposition Robot bidding somewhat). It also appears that the Robot doesn't take the cost of errors into account. Playing the CA when partner has the CK will cost an overtrick, but ducking when declarer has the CK will likely give away a vulnerable game at IMPs (and those diamonds in dummy certainly do appear threatening). A human would obviously weigh the probability that partner led from JT8X versus from KJTx, as well as consider the consequences of making the "wrong" play in each case.

 smerriman, on 2024-May-26, 02:48, said:

3 is described as natural with biddable clubs!? And 3NT is described as extra values (15-17) and a "partial stop in clubs".. that point range is completely impossible to begin with. But anyway, it trusts inferences from its partner more that it trusts the opposition's bidding.


I had four of them, did't I? :) And (very modest) extra values.


I have started to accept that (similar to playing with humans) that sometimes the Robot will hand me a huge gift (defensive error), and sometimes it will hand those gifts out to other people playing the same hand. I have also begun to take amusement from bamboozling the Robot, and while not particularly relevant to this topic, I have a humorous example of that. I arrived in an absolutely hopeless 3NT contract, and an early defensive error by the Robot got me up to eight tricks. I (South) had AQT98 in my hand opposite 65 in dummy. The bidding indicated that West held the club honors, so I led the C8 from my hand, which held when Robot failed to cover (my ninth trick).

So let me move on to my question - does the Robot do these simulations in real time (and how does it do it?)? It really surprised me (the first time I saw it) that the Robot will take different actions (at least in defense and declarer play) in absolutely identical circumstances. This hand occurred during one of my first few sessions in IMPs, and I had written it up meaning to make it my first post (as a question), but will include it here.



Initially, I gave myself too much credit for good defense (and learned the truth after I reviewed what happened at the other tables).

Let me take care of the two oddities first. At one table, South overcalled the 1H opening bid with 3C (holding AQJ98), which "worked," as (after a negative double by W) East bid 3NT (West didn't pull), and that failed by three tricks (+10.6 IMPs). At another table, South raised to 3D, and then to 5D over 4S. That didn't work, as West doubled, and suboptimal play led to a three-trick set.

At the other fourteen tables, West played 4S (doubled at two tables), making at every table except for mine. Ten times the bidding proceeded as shown in the diagram. At one table South bid 3D over the support double, at one table South bid 3C over the support double, and at two tables, South overcalled 2C directly, leading to this auction:

 W  N  E  S
      1H 2C
2S 3D  P  P
4S  X  P  P
 P


I hadn't realized before that the Robot can chose different actions (at different tables) in identical circumstances.

At one table in 4SX, the robot led the DA, and at the other table (same auction), the Robot led the CT.

At the table where South bid 3C over the support double, the robot led the C3 (I don't know why not the CT). At the table where South raised diamonds over the support double, the robot made the odd (and very unsuccessful) lead of the HA.

Finally, at the ten tables with identical auctions, the robot led the CT nine times. South took two clubs, and then shifted to a diamond (seven times), continued clubs (once), or shifted to a spade (once - the correct play, but a trick too late). For some reason I can't figure out, at my table, the robot led the S8, an absolutely devastating lead (but it still required the defense not to slip up in subsequent play). Declarer won in dummy and ruffed a heart, which revealed the heart position to me at trick two. The Souths at the other tables didn't know that declarer had absolutely no chance of setting up the hearts. When declarer played a club to the king at trick three, I won, and returned a second trump, also won in dummy. Declarer ruffed another heart, and then led a diamond towards dummy. Partner won the ace, and played his second club, which I overtook. I then played my third trump, and with no club ruffs available, the contract failed by two tricks. While I thought that would score well, the result exceeded my expectation (+10.3 IMPs). It turns out though, that I hadn't really done anything brilliant at all. The robot set up the defense with the trump opening lead, and I strongly suspect that had I received the lead of the CT (which occurred at all of the other tables with the same auction), I would not have found the necessary spade shift at trick two, which could still have beaten the contract one trick.

Anyway, I have since seen many cases where the Robot will make a different lead or card play at different tables in identical situations, which frequently leads to large swings, and I just wonder why that happens.

Anyway, thanks again for your reply, and I will read the posts in your signature.
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#4 User is offline   smerriman 

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Posted 2024-May-26, 14:42

 1175, on 2024-May-26, 06:52, said:

But shouldn't the Robot take into consideration that his partner might have led from JT8x? If East would absolutely never do that, then ducking makes some (a small amount) of sense. While I appreciate your comment about not trusting opposition bidding (I have seen humans make some, let me say "strange" bids in the duplicate IMPs, that work out incredibly well a surprising percentage of the time), I think that in this case, East doesn't have "room" for the CK (I would at least trust the opposition Robot bidding somewhat). It also appears that the Robot doesn't take the cost of errors into account. Playing the CA when partner has the CK will cost an overtrick, but ducking when declarer has the CK will likely give away a vulnerable game at IMPs (and those diamonds in dummy certainly do appear threatening). A human would obviously weigh the probability that partner led from JT8X versus from KJTx, as well as consider the consequences of making the "wrong" play in each case.

Like I said at the very end, the old version of GIB I have *does* take this into account, and causes it to play the Ace. Why didn't yours? Most likely because you are playing with the free robot, which has been severely crippled from the proper product, with one example being that the number of hands it simulates is very low. Of course, paid robots are still capable of making equally silly mistakes; I don't know the exact logic for how it determines how many mismatching hands to include in the sample, and how far they're allowed to mismatch.

If in a similar situation there was a very unusual hand East might hold that lets game make, should you play safe to ensure you gain 12 IMPs every time it occurs, even if 90% of the time you'll cost yourself 3 IMPs? How do you determine what assumptions you've made are less likely than others? Weighting possible deals is a very difficult problem..

But as usual, not saying GIB couldn't do it better, though it's trickier than it sounds.

 1175, on 2024-May-26, 06:52, said:

I had four of them, did't I? :) And (very modest) extra values.

Yeah, I wasn't referring to your choice, more that GIB's definition is ludicrous in the first place, which doesn't help things.

 1175, on 2024-May-26, 06:52, said:

So let me move on to my question - does the Robot do these simulations in real time (and how does it do it?)? It really surprised me (the first time I saw it) that the Robot will take different actions (at least in defense and declarer play) in absolutely identical circumstances.

GIB randomly generates a set of hands that it believes matches the bidding and play so far (with some leeway, as above), and uses that to make a decision. If you are playing in any form of robot *tournament* on BBO (both free and paid - Daylongs, challenges, or any other tournament setting with robots), the random seed is synchronised across tables. So if every bid and play is identical up to a certain point, that random sample will also be identical, so it will come up with the identical action at other tables.

But any minor variation will mean they're no longer synced, which is why you can get frustrating occurrences where following suit with a different small spot card can cause a contract to make at one table and not other.

I suspect none of this synchronisation applies if you're playing the anonymous IMP game, so you'll get random variation even if everything is identical.
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#5 User is offline   kontoleon 

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Posted 2024-June-08, 21:29

I play with robbot by a lot, (over 2000 every month from years) and I don't even log in just because I hate to play with unknown humans. Robbot defence much deference than human, but this is not auto D. He leads usually really passive yes, and many times miss garandee and easy defence just because he put on deference spot some cards by bid.

Many times miss some great change, just take the Ace with no real reasons, and miss defence from this reason,even when he was playing attacker (dicleare)

Some times even lead singleton minor on NT, with out even i bid this one! (singleton major I do often too anyway). Many times he just miss the opportunity to go down and just duck with no real reason.

But many times he make super great defence anyway. But the real problem was too many tricks that you can easy break when you defence (with the robbot).

But is unfair to said defence D, just because he not play as human style., but I agree was real poor defence and not only defence anyway.
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#6 User is offline   thepossum 

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Posted 2024-June-08, 22:29

I dislike passive leads on the whole, but if you can't think of a good lead no harm in doing anything you feel like
I am biased by not really caring about how many extra under or overtricks you can make
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#7 User is offline   1175 

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Posted 2024-June-08, 23:13

The robot seems oddly random at times. What would you lead (and what do you think the robot led) on this hand?



I will follow up with the answer later.
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#8 User is offline   smerriman 

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Posted 2024-June-09, 17:53

I assume the robot didn't make the obvious K lead :) The fact you posted about it makes me want to lean towards one of the most unlikely leads, so I'll guess the 5, just because I know once in a blue moon it leads low from a doubleton and nobody knows why.
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Posted 2024-June-09, 21:37

 smerriman, on 2024-June-09, 17:53, said:

I assume the robot didn't make the obvious K lead :)


I don't know if I would describe the K lead as "obvious" against a grand slam (I would certainly lead it against a small slam to try to set up a trick). It could backfire if South has a stiff club (reasonably likely) and North has AJT of clubs (close to the actual situation - South had a singleton J, and North had A98, instead of AT9).

I think this auction screams for a trump lead (very unlikely to damage the defense), which the robot seems more fond of than humans in general (though, for some reason, not in this situation). Anyway, no lead can beat the contract, but (among other things) an opening lead shouldn't give declarer a map of how to play the hand. The robot led the 2, and I "strongly suspected" that West had the Q. I therefore abandoned any thought of taking the heart finesse, and had to play for West to have four or more spades, as well (which, fortunately for me, West did). On many layouts though, the heart lead could give away the contract at trick one.



Edited to add: I actually found some notes I wrote at the time I played this hand. Two other tables attempted 7, and failed. At both, South bid 4NT (a bid which has obvious flaws) in response to the 1 opening bid and those auctions induced East to lead the K (anyone who would jump to 4NT opposite the opening bid might not have found the squeeze regardless of the lead). Making 7 scored +14.7 IMPs.
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#10 User is offline   smerriman 

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Posted 2024-June-09, 23:11

 1175, on 2024-June-09, 21:37, said:

On many layouts though, the heart lead could give away the contract at trick one.

It could resolve a guess, yes, though remember the robots assume declarer will play with all hands visible, so finding partner with Qx (or Qxx like here) will never "cost" in the robots mind, even though it will in reality. (Which is why it likes to lead singleton Ks offside too). It's probably difficult for it to find a deal where leading a heart actually costs double dummy (though point taken about the clubs).
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Posted 2024-June-21, 19:48

I will add this hand here rather than starting another thread.



The Robot led the K, and then... shifted to a spade (never necessary, as West can have only one spade), giving away the contract. How did the Robot conclude that a shift would produce a better result?
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#12 User is offline   smerriman 

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Posted 2024-June-21, 20:17

View Post1175, on 2024-June-21, 19:48, said:

How did the Robot conclude that a shift would produce a better result?

Wrong question - given 2 vulnerable with Jxxxxx isn't even remotely on its radar, the robot's question is on what hand where you have a legitimate 2 bid does shifting to a spade cost? As usual, it believes you no matter what. (And as usual, not saying that's a good idea.)

Note also that GIB does not assume anything about previous plays; the fact the K won the trick has zero influence on who it thinks could hold the A (even if ducking would have been a 100% losing option).
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Posted 2024-June-22, 06:22

View Postsmerriman, on 2024-June-21, 20:17, said:

Note also that GIB does not assume anything about previous plays; the fact the K won the trick has zero influence on who it thinks could hold the A (even if ducking would have been a 100% losing option).


I don't understand (in this case) why, whatever caused the Robot to lead the K in the first place (presumably, simulations that indicated it could get a club ruff), wouldn't cause it to continue clubs at trick two.
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Posted 2024-June-22, 06:56

Continuing on this sub-topic, I have to say that the Robot making poor defensive shifts easily ranks as the most frustrating aspect of playing with it.

This one (just played) made me want to scream:



Only fifteen tables played this hand. At two tables, South found a 2 bid over 2. At one of those tables, this scared East-West out of 3NT, especially after North raised diamonds. At that table, East played 5, failing by one trick (which probably should have made after a spade lead, losing to the king, and a spade return). An the other table where South bid 2, he rebid them after North's 3 raise and East's 3 bid. North eventually bid 5 over 5, which (down two doubled) ended up as a slightly profitable sacrifice.

Thirteen tables saw the auction shown, and at every one of those, North found the somewhat inspired lead of the K, which declarer ducked. Any intermediate would see the need to kill the club suit (if partner has Qxxx), and continue diamonds at trick two to remove the A as an entry. At twelve tables, the Robot shifted to a heart at trick two (once the 8, all other times the deuce) - even after the T from declarer. At the final table, South (someone who has apparently learned the foibles of the Robot) induced a diamond continuation by throwing the Q at trick one. This led to a three-trick set (+13.3 IMPs).
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#15 User is offline   smerriman 

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Posted 2024-June-23, 02:38

 1175, on 2024-June-22, 06:22, said:

I don't understand (in this case) why, whatever caused the Robot to lead the K in the first place (presumably, simulations that indicated it could get a club ruff), wouldn't cause it to continue clubs at trick two.

Sure, at trick 1 it was *hoping* for a ruff, and didn't know if there were spade tricks. At trick 2, it *knew* that if there was a club ruff, it'd take it after you cashed your guaranteed spade winner.

 1175, on 2024-June-22, 06:56, said:

Any intermediate would see the need to kill the club suit (if partner has Qxxx), and continue diamonds at trick two to remove the A as an entry. At twelve tables, the Robot shifted to a heart at trick two (once the 8, all other times the deuce) - even after the T from declarer. At the final table, South (someone who has apparently learned the foibles of the Robot) induced a diamond continuation by throwing the Q at trick one. This led to a three-trick set (+13.3 IMPs).

Yeah, unfortunately this is just going to happen with Monte Carlo samples, especially with the free robot where the sample size is so ridiculously tiny - with West having 12+ HCP, there's a fair chance none of the sample will have you holding Qxx+ in clubs and declarer no other diamond stopper. That's a big difference between robots (deal hands randomly and see what happens) and humans (determine exactly what cards need to be held in order to defeat the contract, and play for that, even if it's a small chance).
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Posted 2024-June-26, 04:32

View Postsmerriman, on 2024-June-23, 02:38, said:

Sure, at trick 1 it was *hoping* for a ruff, and didn't know if there were spade tricks. At trick 2, it *knew* that if there was a club ruff, it'd take it after you cashed your guaranteed spade winner.



I would argue that cashing that "guaranteed spade winner" can wait until after the club ruff. :)
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#17 User is offline   smerriman 

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Posted 2024-June-26, 05:24

View Post1175, on 2024-June-26, 04:32, said:

I would argue that cashing that "guaranteed spade winner" can wait until after the club ruff. :)

How so? Remember to GIB there is a 100% assumption you hold the spade ace, but it has no idea who holds the club ace. If declarer does, playing a club will quickly lead to that spade trick disappearing.. so it has to take that first.

Of course, the assumptions are wrong, but the logic based on them seems correct.
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Posted 2024-June-26, 23:45

View Postsmerriman, on 2024-June-26, 05:24, said:

How so? Remember to GIB there is a 100% assumption you hold the spade ace, but it has no idea who holds the club ace. If declarer does, playing a club will quickly lead to that spade trick disappearing.. so it has to take that first.

Of course, the assumptions are wrong, but the logic based on them seems correct.


Not sure I buy that logic. Where would the spade trick go? Most likely on diamonds. Consider an "alternate" hand (switching just a couple of cards):



With this hand, I suppose you could call the spade shift "correct," but (to work) it depends on declarer having made a huge error by not winning the A at trick one (always possible with the Robot, I guess :) ).
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#19 User is offline   smerriman 

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Posted 2024-June-27, 00:50

View Post1175, on 2024-June-26, 23:45, said:

With this hand, I suppose you could call the spade shift "correct," but (to work) it depends on declarer having made a huge error by not winning the A at trick one (always possible with the Robot, I guess :) ).

Yup, thus my earlier comment:

View Postsmerriman, on 2024-June-21, 20:17, said:

Note also that GIB does not assume anything about previous plays; the fact the K won the trick has zero influence on who it thinks could hold the A (even if ducking would have been a 100% losing option).

But even if such a hand didn't exist, while everyone is in agreement about poor assumptions (arguably GIB's greatest flaw), to accept your theory that GIB's shift is a mistake even given its assumptions, you need to find examples where the the spade shift scores strictly less than the club when South has Ace 6th in spades. What hand layout are you thinking of there?
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Posted 2024-June-27, 04:39

View Postsmerriman, on 2024-June-27, 00:50, said:

But even if such a hand didn't exist, while everyone is in agreement about poor assumptions (arguably GIB's greatest flaw), to accept your theory that GIB's shift is a mistake even given its assumptions, you need to find examples where the the spade shift scores strictly less than the club when South has Ace 6th in spades. What hand layout are you thinking of there?


I just prefer to concentrate on one defensive task at a time. :) On the original hand, South actually could hold a stronger hand (say AJxxxx,x,xxx,Axx). In this case, a Robot holding the South hand might (after a spade shift) lead a low club ("assuming" that partner led from KQ). Granted, with the opponents at the 5-level, that would only cost an overtrick.

I wish I had kept track of the number of Souths that bid 2. Yes, that bid has "flaws," but (by making the opponents play at the 5-level), it gave North-South a chance for a huge pickup. I have quickly learned that to do well against the Robots, one must often bid non-existent values.
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