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Gib Screws up 3-card ending

#1 User is offline   xeno123 

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Posted 2017-May-04, 10:46

At trick 10, GIB underleads its Ace where it can only cost a trick given the King is out - declarer is known to have two trumps and so only room for a singleton heart.

http://tinyurl.com/lhquqpe
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#2 User is offline   shyams 

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Posted 2017-May-05, 03:07

View Postxeno123, on 2017-May-04, 10:46, said:

At trick 10, GIB underleads its Ace where it can only cost a trick given the King is out - declarer is known to have two trumps and so only room for a singleton heart.

http://tinyurl.com/lhquqpe

From West's perspective, it is crazy unlikely for East to bid 4 without the K -- especially given the vulnerability.

So, "knowing" that East has K, the West Robot IMO believes that "all cards are equal" and leads any heart.
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#3 User is offline   gwnn 

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Posted 2017-May-05, 03:46

This is a play that can never gain but will often break even, so technically it can still be a result of Monte Carlo simulations. I think it's a bit much to ask for a fix that can distinguish "works on any distribution" from "works on any distribution simulated". Although I would really like more simulations or I would like to know whether GIB sometimes just gives up on simulating, which seems to be the case.
... and I can prove it with my usual, flawless logic.
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#4 User is offline   xeno123 

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Posted 2017-May-05, 09:30

View Postgwnn, on 2017-May-05, 03:46, said:

This is a play that can never gain but will often break even, so technically it can still be a result of Monte Carlo simulations. I think it's a bit much to ask for a fix that can distinguish "works on any distribution" from "works on any distribution simulated". Although I would really like more simulations or I would like to know whether GIB sometimes just gives up on simulating, which seems to be the case.


Yes, I agree that is what happened. I've seen it before, mostly in the context of when a player has "lied" during the bidding.

There is a relatively simple fix - near the end of the hand run a handful of simulations with all inferences from bidding turned off. Or even simpler, if two cards are equivalent, play the higher one!
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