BBO Discussion Forums: GIB Fails to lead AK against 6NT; leads it against 6C - BBO Discussion Forums

Jump to content

Page 1 of 1
  • You cannot start a new topic
  • You cannot reply to this topic

GIB Fails to lead AK against 6NT; leads it against 6C

#1 User is offline   42krunner 

  • PipPipPipPip
  • Group: Full Members
  • Posts: 145
  • Joined: 2013-April-10

Posted 2015-September-27, 10:19

8 board robo-dup, MP's.

About half field in 6NT with exact same auction and result. Most of the rest of the field was in 6C going down when GIB leads the AK.

link

Daniel
0

#2 User is offline   steve2005 

  • PipPipPipPipPipPipPip
  • Group: Advanced Members
  • Posts: 3,152
  • Joined: 2010-April-22
  • Gender:Male
  • Location:Hamilton, Canada
  • Interests:Bridge duh!

Posted 2015-September-27, 11:54

old bug. they fixed it for 7N. same thing 7 of suit cashes 7N doesn't lead Ace.
programmers fixed by making GIB cash 1 trick if available against 7N rather than simulating hands.

Do programmers have to put same fix to cash with 2 tricks against 6N?
Sarcasm is a state of mind
0

#3 User is offline   42krunner 

  • PipPipPipPip
  • Group: Full Members
  • Posts: 145
  • Joined: 2013-April-10

Posted 2015-September-27, 12:01

Is it a bug or does GIB actually think it can have a good chance of setting it two? I don't see how, even with the "lie" 3NT bid.
0

#4 User is offline   steve2005 

  • PipPipPipPipPipPipPip
  • Group: Advanced Members
  • Posts: 3,152
  • Joined: 2010-April-22
  • Gender:Male
  • Location:Hamilton, Canada
  • Interests:Bridge duh!

Posted 2015-September-27, 16:50

 42krunner, on 2015-September-27, 12:01, said:

Is it a bug or does GIB actually think it can have a good chance of setting it two? I don't see how, even with the "lie" 3NT bid.

it runs a simulation and if it thinks it has 50.00000001% chance of getting on average greater than 2 tricks it leads something else.
Where the real problem comes I think is it simulations it runs it still gets 2 tricks with other leads so sees no difference from leading a random card than leading AK
Sarcasm is a state of mind
0

#5 User is offline   johnu 

  • PipPipPipPipPipPipPip
  • Group: Advanced Members
  • Posts: 4,928
  • Joined: 2008-September-10
  • Gender:Male

Posted 2015-September-27, 17:21

IMHO, cashing the first 2 tricks in a small slam is overrated :) It's much more suspenseful to win the last 2 tricks so I think GIB is just trying to make the hand interesting until the last card.
0

#6 User is offline   Bbradley62 

  • PipPipPipPipPipPipPipPip
  • Group: Advanced Members
  • Posts: 6,542
  • Joined: 2010-February-01
  • Gender:Male
  • Location:Brooklyn, NY, USA

Posted 2015-September-27, 22:53

I'd like to know what hands West simulated. West is looking at 7HCP; North announced 13-15 and South announced 20-21. So, the two-part question is:
  • how many tricks can declarer cash outside of diamonds?
  • is there any chance of EW taking 3 tricks?

If West cashes AK, EW gets exactly 2 tricks. I don't see any reasonable simulation that yields EV(EW)>2 if West leads anything else.
0

#7 User is offline   1eyedjack 

  • PipPipPipPipPipPipPipPip
  • Group: Advanced Members
  • Posts: 6,575
  • Joined: 2004-March-12
  • Gender:Male
  • Location:UK

Posted 2015-September-27, 23:20

 Bbradley62, on 2015-September-27, 22:53, said:

I'd like to know what hands West simulated. West is looking at 7HCP; North announced 13-15 and South announced 20-21. So, the two-part question is:
  • how many tricks can declarer cash outside of diamonds?
  • is there any chance of EW taking 3 tricks?

If West cashes AK, EW gets exactly 2 tricks. I don't see any reasonable simulation that yields EV(EW)>2 if West leads anything else.

I don't think that your final sentence gets to the root of the problem. Also of relevance are sims that result in fewer than 2 tricks for the defence.

Suppose that it runs 1000 sims of various leads all of which lead to precisely 2 tricks for the defence. How is GIB to choose from among THOSE simulated leads the ones that involve cashing the first two tricks?

A possible solution, if programmable, would be to place higher priority on earlier tricks than later tricks. Then if two sims otherwise appear equally profitable, the one that takes those tricks earlier in the play would be chosen.
Psych (pron. saik): A gross and deliberate misstatement of honour strength and/or suit length. Expressly permitted under Law 73E but forbidden contrary to that law by Acol club tourneys.

Psyche (pron. sahy-kee): The human soul, spirit or mind (derived, personification thereof, beloved of Eros, Greek myth).
Masterminding (pron. mPosted ImagesPosted ImagetPosted Imager-mPosted ImagendPosted Imageing) tr. v. - Any bid made by bridge player with which partner disagrees.

"Gentlemen, when the barrage lifts." 9th battalion, King's own Yorkshire light infantry,
2000 years earlier: "morituri te salutant"

"I will be with you, whatever". Blair to Bush, precursor to invasion of Iraq
0

#8 User is offline   cloa513 

  • PipPipPipPipPipPip
  • Group: Advanced Members
  • Posts: 1,528
  • Joined: 2008-December-02

Posted 2015-September-28, 20:07

 1eyedjack, on 2015-September-27, 23:20, said:

I don't think that your final sentence gets to the root of the problem. Also of relevance are sims that result in fewer than 2 tricks for the defence.

Suppose that it runs 1000 sims of various leads all of which lead to precisely 2 tricks for the defence. How is GIB to choose from among THOSE simulated leads the ones that involve cashing the first two tricks?

A possible solution, if programmable, would be to place higher priority on earlier tricks than later tricks. Then if two sims otherwise appear equally profitable, the one that takes those tricks earlier in the play would be chosen.

That fails to explain how it manages to make the "correct lead" with clubs every time- simulations should have told it not to lead out AK for a risk of a ruff and its supposed to have already a preference for 2 down over a possible 3 down.
0

#9 User is offline   Bbradley62 

  • PipPipPipPipPipPipPipPip
  • Group: Advanced Members
  • Posts: 6,542
  • Joined: 2010-February-01
  • Gender:Male
  • Location:Brooklyn, NY, USA

Posted 2015-September-30, 00:41

 1eyedjack, on 2015-September-27, 23:20, said:

 Bbradley62, on 2015-September-27, 22:53, said:

I don't see any reasonable simulation that yields EV(EW)>2 if West leads anything else.


I don't think that your final sentence gets to the root of the problem. Also of relevance are sims that result in fewer than 2 tricks for the defence.

Suppose that it runs 1000 sims of various leads all of which lead to precisely 2 tricks for the defence. How is GIB to choose from among THOSE simulated leads the ones that involve cashing the first two tricks?

A possible solution, if programmable, would be to place higher priority on earlier tricks than later tricks. Then if two sims otherwise appear equally profitable, the one that takes those tricks earlier in the play would be chosen.

I guess my statement should have been that I don't see any reasonable simulation that yields EV(EW)>=2 if West leads anything other than the cashing tricks. As you point out, there is always a probability of taking fewer than 2, and there should be virtually no probability of take more than 2, so the expected value should be less than 2.
0

#10 User is offline   1eyedjack 

  • PipPipPipPipPipPipPipPip
  • Group: Advanced Members
  • Posts: 6,575
  • Joined: 2004-March-12
  • Gender:Male
  • Location:UK

Posted 2015-September-30, 01:02

Yes I phrased my response poorly.

My point being, as I expect that you realise, that in general, not just on this hand, an early trick should be regarded as more valuable than a later trick (all other factors being equal), simply because an early trick has greater confidence of banking. Ie, the program should appreciate that where it simulates a later trick there should be a built-in acceptance of the possibility that it might not materialise even if no actual simulations demonstrate it. If specific simulations do generate a disparity in the number of tricks, whether more or fewer, then by all means that should take priority over this principle.
Psych (pron. saik): A gross and deliberate misstatement of honour strength and/or suit length. Expressly permitted under Law 73E but forbidden contrary to that law by Acol club tourneys.

Psyche (pron. sahy-kee): The human soul, spirit or mind (derived, personification thereof, beloved of Eros, Greek myth).
Masterminding (pron. mPosted ImagesPosted ImagetPosted Imager-mPosted ImagendPosted Imageing) tr. v. - Any bid made by bridge player with which partner disagrees.

"Gentlemen, when the barrage lifts." 9th battalion, King's own Yorkshire light infantry,
2000 years earlier: "morituri te salutant"

"I will be with you, whatever". Blair to Bush, precursor to invasion of Iraq
0

Page 1 of 1
  • You cannot start a new topic
  • You cannot reply to this topic

1 User(s) are reading this topic
0 members, 1 guests, 0 anonymous users