[xeno123]

I've seen the basic bots stupidly discard a boss card in a suit when they still have a low card available, but this is the first time I've noticed a tournament bot do this (someone else was declarer here):

http://tinyurl.com/mnrha8l

In the 3-card ending, the bot playing East discards the A♣ instead of the 10♣ on the play to the 11th trick. Any possible logic for doing this, or is it a bug? Declarer has only one unknown card at the time of the discard, and the discard of the A♣ can only ever hurt (as it did here). If declarer had a heart instead of another club, then the discard makes no difference, but that is inconsistent with the bidding (declarer denied a four card major). I suppose it could be that the initial underbid by declarer lead the bot to assume that West had the K♣ in which case the discard makes no difference. But the logic here should be to go with the play that dominates (as good or better in all circumstances).

I must say the tournament bots in general really do play (and in particular defend) a lot better than the basic bots!

Peter

[Lord Molyb]

It thought you had just a 2 low clubs left since you opened 1NT with 20 points and had already turned up with 5 diamonds and 17 HCP.
Basically, you confused it.

[manudude03]

Declarer has already discarded on spades though, so throwing the ace of clubs is a no-win play.

[Antrax]

Yes, it's a no-win play but that's not how GIB thinks. GIB knows declarer has ♣xx left so it doesn't matter what it pitches, so it pitches whatever. The thought of the ♠ always being a safe discard unless declarer revoked and the ♣A being safe only if declarer counted his HCP correctly doesn't enter its head.

[Lord Molyb]

manudude03, on 2013-June-14, 16:42, said:

Declarer has already discarded on spades though, so throwing the ace of clubs is a no-win play.

fixed, didn't read play thoroughly

[xeno123]

Antrax, on 2013-June-14, 21:55, said:

GIB knows declarer has ♣xx left so it doesn't matter what it pitches, so it pitches whatever.

So an easy fix is to pitch the lower card when it wants to pitch "whatever."

This particular issue doesn't seem to come up much with the advanced bots, but it comes up a lot with the basic bots.

[Antrax]

It's an easy fix for a human. Not sure how easy it is for GIB (AFAIK it has no rules when playing the hand, only simulations).
More to the point, is this really the problem with GIB, that psyching 1NT with a 2NT opener makes it give up an overtrick? Assuming you have limited time to work on it, wouldn't you rather fix something else?

[xeno123]

Antrax, on 2013-June-15, 21:09, said:

It's an easy fix for a human. Not sure how easy it is for GIB (AFAIK it has no rules when playing the hand, only simulations).
More to the point, is this really the problem with GIB, that psyching 1NT with a 2NT opener makes it give up an overtrick? Assuming you have limited time to work on it, wouldn't you rather fix something else?

It is an easy fix - if the simulations say that GIB is indifferent between two cards of the same suit, then discard the lower one.

I grant this particular example with the !NT psyche (not by me I would add!) is in and of itself not that important, but with the basic bots this sort of error happens much more, even without a psychic bid. I assume the smaller number of simulations lead to more cases where it doesn't seem to matter what discard to make, even when in fact it does.

[FM75]

It looks like an error. At the time of GIB's discard, it is only a 4 (unknown) card ending. 12 possible hands. In none of those combinations is it advantageous to discard the club ace.

That said, if GIB correctly decides that there is no difference between two discards, then there is clearly no reason to prefer the lower of two cards.

[manudude03]

FM75, on 2013-June-17, 15:47, said:

It looks like an error. At the time of GIB's discard, it is only a 4 (unknown) card ending. 12 possible hands. In none of those combinations is it advantageous to discard the club ace.

[nitpick]Only 6 possible hands, you're double-counting.[/nitpick]

[FM75]

manudude03, on 2013-June-18, 03:58, said:

[nitpick]Only 6 possible hands, you're double-counting.[/nitpick]

Yup. Thanks.