smerriman

Seems GIB's system leaves it stuck for a bid - 4♣ is gerber?! 4♦ and 4♥ are Texas, and 4nt apparently denies a 5 card major. Can't say responses to 3NT openings should be high on the priority list though.

I'm primarily thinking of daylongs, where there is no EW. Getting dealt a 'hard' board allows good players to get a good score; getting dealt an 'easy' board drags your score too heavily towards 50%. An 'easy' 50% should drag your score less towards 50% than a 'hard' 50% where you could/should have done better.

GIB plays support doubles, so double (or redouble in this case) is to show precisely 3 card support - you use spade raises to guarantee 4. So I can't see how GIB has any choice but to pull to 5♣ - you showed strength for game, and a 9+ card fit surely has to be better than a 7 (and guaranteed not 8) card one. GIB knows you bid game without knowing about his 4 clubs after all! GIB would bid 3♠ (4+ ♠, 16-18 total points), but you also have 4♠ (4+ ♠, 19-22 points) or 3♦ (4+ ♠, 1- ♦, 19-22) points to choose from if you want to force to game.

Redouble shows exactly 3 spades. Opponents showed 10 diamonds, so GIB knows you have at most a singleton. That leaves 9 cards in clubs and hearts, so you must have at least 5 clubs. You're going to be hard pressed to get GIB to prefer a Moysian spade fit over a 9 card club fit.

Yeah, obviously the above was a very simplified example - but the scoring system itself has nothing to do with whether anyone plays "optimally" or not; that was just an example of how it gives a different result from MPs. Someone who overbids to 6NT will get 100% or 0% at full weighting regardless of scoring. It's solely a way of weighting hands, based on everyone's actual results for that hand, due to the fact that eg a 50% score on a flat board is not the same as a 50% on a swingy board. (I haven't defined the exact formula for what the weighting would be based on the results.)

(Was tossing up whether to post this here or in the BBO discussion forum; while it sprung from daylongs, it's sort of a general scoring idea as well so ended up going here). I've been thinking a lot recently about the use of MPs in daylong tournaments where not everybody plays the same hands. There have been plenty of threads in the past about the fact not everyone plays the same hands, and that can have a heavy influence on the scores - if you're dealt a flat hand, you might have zero chance of winning the tournament no matter how well you play. While winning any bridge tournament requires some luck (the optimal line may not succeed), playing the same hands is crucial to MPs, especially the way that ties are worth half a matchpoint. Suppose for a moment that hands are always dealt in such a way that optimal play works out best. Any scoring method should therefore ensure that optimal play will place you in first place overall. A starting idea would be to adjust the matchpoint formula so that the top score on each board is 100%. This of course doesn't work because now the situation is flipped - a flat hand that used to be worthless is now overvalued. However, what if we extend that to the idea of a weighted average. A completely flat board gets you 100% - but that board then carries 0 weight, not counting at all. A board where you beat everyone else gets you 100%, with a full weighting of 1 board. At the end, you add up your weighted percentage, and divide by the number of 'boards' you've played, for your final score. Consider two types of board: Hard board: 20% of players will score maximum, 80% minimum. Easy board: 80% of players will score maximum, 20% minimum. Person A receives two hard boards, succeeding once and failing once. Under MP scoring, he receives a score of 65%. Person B receives two easy boards, succeeding both times. Under MP scoring, he only receives a score of 60%. Person C gets one easy board, and one hard board, winning the easy board only. Under MP scoring, he gets 50%. Now considered a weighted score. Playing the first board well gets you 100%, and counts as 0.8 boards. Playing it badly gets you 0%, counting as 0.2 boards. The reverse applies to the second board type. Person A now has a score of (100% * 0.8 + 0% * 0.2)/1.0 = 80% Person B now has a score of (100% * 0.2 + 100% * 0.2)/0.4 = 100%. Person C now has a score of (100% * 0.2 + 0% * 0.2)/0.4 = 50%. Person B wins due to playing optimally. True, it was harder for Person A to win - but at least they had the opportunity, and this will balance out over a larger number of hands. The idea is the harder it is to score well, the more it should count if you do, and the less it should count if you don't. (With weightings based on how everyone else actually played - assumes enough people played to make this realistic). Thoughts?

But surely as I mentioned initially, this will happen too often to make it worthwhile? While you can still make the contract, you're down to a 50/50 shot at best on guessing the heart King immediately (less if you can't guarantee reading the squeeze position) if North has any club honor (singleton/doubleton/doesn't matter); compared with the original line which works if clubs are 2-2 OR the heart king is onside.

Being in the expert forum, I'm guessing South holds the heart King and clubs aren't 2-2. Also, being in the expert forum, I'm going to allow myself the use of the GIB button while playing around with hands, since I'm not an expert :) If South does indeed hold the heart king, it seems that the contract can always be made by ducking a club immediately (even if clubs are 2-2) - and in most cases this is the only line that works. Assuming a diamond is returned, we win with the Ace, then run clubs. On the last club, North has to keep SQx and two other cards. If North keeps two diamonds, then we have to discard the heart Queen and play to the heart Ace; the spade K then squeezes south in hearts and diamonds, with the 9 of hearts the threat. If North keeps two hearts, we have to discard the spade Jack. Then again South gets squeezed in hearts and diamonds, but this time with the Q of hearts the threat. I'm not sure how easy it is to tell what North has kept though. Also, if North wins the first club and immediately returns a heart, instead of a diamond, the contract is still makeable - by playing the Ace and working on another squeeze. But this line fails immediately if North had the King of hearts after all, which seems to imply ducking a club is too dangerous compared with a line like nige1's..

Well, with basic GIB, the entire auction is replicated except for the final double. So it's not just a rules error - somehow the hands GIB simulated had double winning? That can't be right.

I'm in.

I can't replicate this - either it was remarkably fixed by the update that was released just after you posted this, or maybe you got the auction wrong. Basic GIB currently actually responds 3♦ instead of 3♥ showing 3+ ♥, 11+ points, and at least the Q of diamonds.. but even if I force a 3♥ respond, it bids 4♥ next turn.

I posted a bug report about this mid-2016, so it's known, just apparently not a priority.

If you can post a screenshot that may help. Have you checked if you have your browser zoomed in? Or perhaps eg you have a browser add-on on similar which covers up the bottom part of the screen.

GIB often passes "forcing" raises of a minor, even if north wasn't a passed hand - see eg http://www.bridgebase.com/forums/topic/74820-another-clearcut-bidding-hole/ which I reported mid-2016 (still occurs).

GIB bids 3NT if East hasn't shown clubs. After the double, since you didn't want to bid no trumps yourself, it only bids 3NT with a club stopper, which isn't unreasonable. Why not just bid 3NT yourself?

None of that is possible with challenges.

For reference, you can skip step 3 entirely.

I agree. Best hand may not be bridge, but defending with robots is even less like bridge. My hope is that one day BBO will bring in an option where best hand means either you or your partner has the best hand; that would add a lot of variety to the auctions.

Seems the real issue is that both 3♠ and 4♠ overcalls are undefined to GIB..

Agreed. There was a thread a while back where jdonn said he agreed that GIB should be tweaked to look for lower level forcing bids instead of just blasting to slam in cases like these. Maybe one day.

Is it just me, or was "do you need to look at your hand" obviously metaphorical, in the sense of "can a non-passing hand exist", not meant to be taken literally like (almost) everyone seems to be doing :unsure:

You might like to read: http://www.bridgebase.com/doc/gib_descriptions.php GIB defines a partial stop as Qx or Jxx - ie a stop if you have help.

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In that case I'd suggest taking screenshots of the results and the key tricks next time - that's the only way you could really conclusively prove it wasn't a human error.

Most likely is that you saw the ace of spades, and didn't see the small winning heart played by the other robot. GIB often plays its cards in an unusual order, dropping a high card on the second to last round to make you think your last card is high when it's not.