smerriman

I ran a quick sim and the chance of a 1♦ opener being 3 cards was 4.6%. Adjusting your sim for the missing hands, the chance of a 1♣ opener being 2 cards was also 4.6% :) So the argument to get them to switch systems is almost as convincing as the argument to not switch.. the point in both cases is that you can just bid as if it won't happen.

I've never found this to be the case. If you open 1♦ with 4432, your 1♦ opener has 4 cards 96% of the time - responder just acts as if they're certain anyway. And the vast majority of those 4% it doesn't matter, since you're usually in a major fit. PS - you're missing the (432)4 shapes.

The 'race to 1NT' is that when values are roughly equally divided between the sides, you'd rather be declaring 1NT than defending it. It doesn't apply at all if the values aren't equally divided. With your hand there's about a 38% chance you have 17 or less points combined, and 53% chance that you have 18 or less points combined, and these alone are going to be very poor scores for you. (You won't only be punished when LHO has invitational values - if you had agreed to play such a system, the opponents surely aren't going to play the same defense as to a strong 1NT overcall; I'd expect RHO would double with extras too, after which LHO could run out if needed.) And that's not including other cases when 1N undoubled is poor too.

What were the actual tricks? Assuming a heart lead, won by declarer who knocks out the ace of trumps, you switch to a spade, declarer finesses, and then your partner didn't play diamonds? Feels like they no choice at that point.

Well, the former has never been in doubt :) For the latter, I don't think the descriptions were actually written for the sake of disclosure / the laws of bridge, and its partner is just as misled. They're written for the entire algorithm to work; if the description was changed to 10+ HCP, then despite being in a game-forcing situation, its robot partner would refuse to bid 3NT later with 13-14 HCP because all of its rules for bidding 3NT are based around things like having at least (25 - partner's shown HCP in the description). So it imposes a lot of the descriptions in order to make future bids work, even if the description itself doesn't match up with the hand or even the logic used to make it. And the fact that its robot partner is forced to make all decisions based on the description being true makes it somewhat closer to legal.

A classic case of GIB adding 2 points for the void in your suit :( The HCP bit isn't part of the rule, it'll also do it with ♠- ♥65432 ♦AJ32 ♣AJ73 as that's three points for the void now. Discounting shortness in partner's suit has been a long time request.

A feature for GIB is any A, K, or QJ combined. GIB used to describe honors as "8421" points, where A=8, K=4, Q=2, J=1. So 8+ 8421 points would show the ace, etc, and here a feature shows 3+. BBO changed the descriptions in 2014 to use suit symbols instead, because according to them most people found 8421 points confusing, so, for example, 8+ in hearts got changed to "♥A". 3 days after BBO made the change, people pointed out that this was far more confusing, given the lack of 'at least', and the fact that 3+ was mistakenly changed to "Q", rather than "QJ+" like it should have been. Barry agreed it needed fixing. Fastforward 9 years..

It's definitely a 1 round force, but it's a mistake to call it 'third suit forcing'. Third suit forcing in that sequence is 2♦.

Of course. But we're talking about them ducking the diamond, after which the contract cannot be made. It's really as simple as clicking the GIB button :)

Only if they play a 4th round of spades to gift you a trick with the jack. Any other defense and you're only taking 1 spade.

I wouldn't have ducked the first diamond as East, seeing there didn't appear to be a side entry anyway.

Well, the thread moved on a bit since then :) But the main reason the pair who led the small spade took it down was because declarer ducked, after which the defense is much easier. If declarer had won, it would still be beatable double dummy, but the contract would likely have made at the table. My comment was in reply to Mike who couldn't see the spade lead working (for that reason), but could see a heart lead beating the contract - and again, it would have beat the contract at the table, despite double dummy saying otherwise. Both cases show the human results are really quite independent from what double dummy shows, so looking and seeing there is a 'killing spade lead' misses the point.

This is a really good example of why it's extremely dangerous to look at double dummy scores, backing up what you pointed out in the other thread. Double dummy says that West leading a low spade at trick 1 is the only way to defeat the contract. If West instead leads a heart - whether the 9 or low - the contract is makeable.. by winning in dummy and immediately leading low to the ten of clubs! If a declarer did that I'd be pretty suspicious :)

I would say a greater display of skill is seeing a spade is the only way to beat the contract double dummy, and being happy that you *didn't* lead it. (In general that is; whether that's the case here, I don't know.)

Yes, your assumption is precisely what it does. It will preempt 4♠ with a solid 13 card spade suit though :) Unfortunately, you just have to live with it :(

Do I get to see dummy and partner's card? :)

That's because there are virtually zero hands where all you need to know after that auction is how many aces partner holds, so what ace-asking system you play isn't really relevant. Bids (including 4NT, which is definitely not asking for aces even if playing any form of Blackwood) are used to share other more important information instead.

Your example is a 3♠ bid in my book. But whatever range 2♠ you play, if partner is inviting, you're going to game when you're on the upper end with 4 trumps - otherwise they would never have invited. So I would describe what you're imagining more as a "game accept" than a "GF" (though it's the same thing).

It's not trying for the overtrick; if North has the promised doubleton of spades, the heart play is required to make the contract in case North holds all the trumps.

If by 'large percentage' you mean 3.9%.. the times it breaks the rules for no reason are super frustrating, but it still followed them on 11694/12164 hands in that study.. and half of those exceptions were underleading an ace vs a suit contract. These exceptions I found back then don't seem to exist in the old version of GIB though; it gives the rule-based lead a 0.3 IMP bonus so when all else are equal, it never picks the wrong one.

OK, figured it out. North led the ♠6 and later continued with the ♠2; GIB assumes opponents play the same lead conventions as itself (4th best here, low from xxx); the only valid holding is 62 doubleton. It deals a couple of mismatching hands, but almost all treat that as fact. Under that assumption, its play is the best line, picking up a 4-0 diamond split where possible. Relying on that assumption against unknown opponents is of course ridiculous, though I do have some sympathy for GIB here, since lead inferences are an important part of the game (and this isn't a case where it had a 100% alternative; it has to judge how likely the breaks are) - the programmers simply didn't tell it that others play differently to itself.

Really odd. 100% replicable with the old version of GIB, but it's also fully aware its plan will go down if South has 5 hearts.. yet continues to pick that over any alternative no matter how many times I try (even undo / redo which often fixes some other bugs). Will have to dig into this one some more..

GIB always prefers minors to majors when jumping over a takeout double. It's really annoying :( Just a case of the rule being too generic - if you have any 5 card suit with the right values, bid it - and it testing bids in the order CDHS.

Correct - there's no grand slam try component to it; it's just forced to bid it.

This should go in the GIB forum, not this one. *Every* GIB auction involving a splinter results in a misunderstanding. GIB will happily splinter itself, but as a human it's highly dangerous splintering opposite it as it has no clue how to respond.. the most common response you see is a cuebid of the splinter suit holding KQxx, so I'm actually somewhat surprised that didn't happen here :) As for GIB opposite GIB, well, I guess it just rarely comes up with most tournaments best-hand. It's really quite bizarre the robot wasn't programmed to handle them better, since responses to splinters are really quite algorithmic. East isn't even trying to hit anything, there's zero planning; it's just told to splinter with any hand with 19+ total points, 4+ support and 0-1 clubs. After that 4NT is just total points based (+3 for the short suits), and West is not even calculating that East may or may not have enough points to hold aces, it just assumes missing 3 KC is impossible in general and is forced to bid 5NT.