Vacant Places

[BrianEDuran]

Hi all

 

I'm reading Birdge Bridge Odds For Practical Players, by Hugh Kelsey & Michael Glauert. It goes over some stuff about Vacant places, but I still have a few questions.

 

1) Anyone have other recommendation on literature on Vacant Placess, online or in english print?

 

2) I don't understand why one should not count suit they only have partial information in. For example if you now RHO has 5 spades and LHO has 2, plus one round of diamonds has been played, they suggest you figure the odds to be 8 (13-5s) to 11, not 7 (13-5s-1d) to 10. They did "imply" that the both following in diamonds does affect the odds, but only slightly, so it would be something like 7.9 to 10.9. But I don't understand why this is the case.

 

3) Great, now that I understand vacant place, how many do I need before the odds vs. a finess come into play? I know that with AJxxx opposite the Kxxx its slight better to play for the drop, but what if I know 1 more vacant place, or two, or three? When does it become time to finess. Is there a table out there about these hands, the a suit combination, but with vacant spaces?

 

Thanks in advance.

 

Brian

[Free]

What's a "vacant place"?

[inquiry]

If you want to play with this concept, easily, try out this webpage

 

http://www.automaton.gr/tt/en/OddsTbl.htm

 

In the calculator you can dial in known cards in various suits.. but be careful, if you start adding the diamonds as in your example, you can generate wrong numbers.. have fun...

 

Also useful to play with for suit splits... honor location and the like.

 

Ben

 

The reason the random diamond discard on a spade proves nothing, is they have to play some card.. it wasn't forced. If they both follow to a diamond, you could use the program to compare 6 known cards in one hand to 3 in the other (instead of 5 to 2). But you already know that the fellow with 2 spades have 11 other cards.. the fact that he shows you one of them is of little mathematical help per se, and no help what soever in the vacant space calculation....

[paulhar]

Interestingly enough, we just recently had a thread on a BBO forum dicussing vacant spaces. Here's the link:

 

http://bridgebase.lunarpages.com/~bridge2/...our%20boss&st=0

 

The first mention of empty spaces is MickyB's post and most of them from that point talk some about it.

[1eyedjack]

Hi all

 

I'm reading Birdge Bridge Odds For Practical Players, by Hugh Kelsey & Michael Glauert.  It goes over some stuff about Vacant places, but I still have a few questions.

 

1) Anyone have other recommendation on literature on Vacant Placess, online or in english print?

Cannot think of any text to improve on Kelsey/Glauert, sorry. In what way do you find this text less than satisfactory? I think this is regarded as the definitive work.

 

2)  I don't understand why one should not count suit they only have partial information in.  For example if you now RHO has 5 spades and LHO has 2, plus one round of diamonds has been played, they suggest you figure the odds to be 8 (13-5s) to 11, not 7 (13-5s-1d) to 10.  They did "imply" that the both following in diamonds does affect the odds, but only slightly, so it would be something like 7.9 to 10.9.  But I don't understand why this is the case.

When they follow to one round of diamonds the only additional information that is available to you, that was not available to you immediately prior to the playing of one round of diamonds, is that neither defender started with a diamond void. The a priori probability of either defender starting with a diamond void is (usually) so small that the elimination of that possibility has no material bearing on the odds in another suit, contrasted with the effect on the odds if you were to take that into account in the vacant spaces.

 

Note that even if you do know the complete count in a side suit you should only adjust the vacant spaces if the defence had no choice but to reveal that count to you. If they volunteered the count unnecessarily then you should be suspicious as to their motive, ie possibly to cause you to miscalculate the vacant spaces.

 

3)  Great, now that I understand vacant place, how many do I need before the odds vs. a finess come into play?  I know that with AJxxx opposite the Kxxx its slight better to play for the drop, but what if I know 1 more vacant place, or two, or three?  When does it become time to finess.  Is there a table out there about these hands, the a suit combination, but with vacant spaces?

There will be hands when the percentage line in a particular suit in isolation will not provide the greatest chance of overall success in the contract. Leaving that possibility aside, when you are down to one missing card which might be finessed or dropped you simply go for the drop when the 4th hand has more vacant spaces than the player following in second position. Just be sure first to adjust the vacant spaces for all available information, ie including restricted choice effects.

 

On the combination that you posted you presumably cashed King and led small toward Ace-Jack, second hand following low. In the absence of a count in a side suit the hand sitting over the AJ has 12 vacant spaces to his partner's 11, favouring the drop. This is consistent with the brute force method of calculating the odds. Now suppose that before testing this suit you tried another suit and forced a count in that suit showing that the person sitting over the AJ had one more card in the side suit than his partner, then the odds are even - the drop is the same as the finesse. If he had two more than his partner then the player who followed in second seat has one more vacant place in total, despite having one fewer card left in his hand, and the finesse is then superior. All this assumes that there is no other information available (somewhat rare).

[winkle]

Take a look at:

 

http://www.rpbridge.net/7z75.htm

[kfgauss]

Hi all

 

I'm reading Birdge Bridge Odds For Practical Players, by Hugh Kelsey & Michael Glauert.  It goes over some stuff about Vacant places, but I still have a few questions.

 

1) Anyone have other recommendation on literature on Vacant Placess, online or in english print?

 

2)  I don't understand why one should not count suit they only have partial information in.  For example if you now RHO has 5 spades and LHO has 2, plus one round of diamonds has been played, they suggest you figure the odds to be 8 (13-5s) to 11, not 7 (13-5s-1d) to 10.  They did "imply" that the both following in diamonds does affect the odds, but only slightly, so it would be something like 7.9 to 10.9.  But I don't understand why this is the case.

 

3)  Great, now that I understand vacant place, how many do I need before the odds vs. a finess come into play?  I know that with AJxxx opposite the Kxxx its slight better to play for the drop, but what if I know 1 more vacant place, or two, or three?  When does it become time to finess.  Is there a table out there about these hands, the a suit combination, but with vacant spaces?

 

Thanks in advance.

 

Brian

1) Anyone have other recommendation on literature on Vacant Placess, online or in english print?

 

There's an article in "For Experts Only" (by the Granovetters) called "The Monty Hall Trap" by Phil Martin (which I haven't actually read, but have heard something of) which discusses the difference between "volunteered" information and information that you "happened upon [randomly]" and how you should use these various sorts of info in your use of vacant spaces (there's also something on this topic in the link above to Richard Pavlicek's website).

 

2)  I don't understand why one should not count suit they only have partial information in.  For example if you now RHO has 5 spades and LHO has 2, plus one round of diamonds has been played, they suggest you figure the odds to be 8 (13-5s) to 11, not 7 (13-5s-1d) to 10.  They did "imply" that the both following in diamonds does affect the odds, but only slightly, so it would be something like 7.9 to 10.9.  But I don't understand why this is the case.

 

This is not, as has been suggested above, simply because the difference is so small. If that were the case, then the second one would be correct but the first would be close.

 

The reason is as follows: Suppose I have 9 diamonds. The chances they split 2-2, 3-1, and 4-0 resp. are: ("3-1" means either way)

 

[x C y is "x choose y": the number of ways to choose y cards from a collection of x cards]

 

2-2: (22 C 11)(4 C 2)/(26 C 13) = 6*13*12*13*12/(23*24*25*26)

3-1: 2*(22 C 10)(4 C 1)/(26 C 13) = 2*4*13*12*11*13/(23*24*25*26)

4-0: 2*(22 C 9)(4 C 0)/(26 C 13) = 2*13*12*11*10/(23*24*25*26)

 

Thus the odds of 2-2 instead of 3-1 (if we rule out 4-0 by playing a round) are:

2-2:3-1 is: 6*13*12*13*12:2*4*13*12*11*13 = 3*12:4*11 = 36:44 = 9:11

 

Suppose we first remove 2 diamonds from the deck:

 

1-1: (22 c 11)(2 c 1)/(24 c 12) = 2*12*12/23*24

2-0: 2*(22 C 10)(2 C 0)/(24 C 12) = 2*12*11/23*24

 

1-1:2-0 is: 2*12*12:2*12*11 = 12:11

 

After you draw a round of diamonds, it's not the case that 1-1 is now more likely than 2-0. You gained no new info except that they weren't 4-0 (again, assuming opps just play random diamonds), so it must still be the case that an original 3-1 split is more likely than an original 2-2 split.

 

The (false) change in the odds (9:11 changing to 12:11) is basically due to there being more ways for them to play from an original 2-2 split (4 ways = 2*2) than from an original 3-1 split (3 ways = 3*1).

 

You can work out the implications for other suits, but this shows that at least for the diamond suit itself, you shouldn't be counting "partial information" in that suit.

 

3)  Great, now that I understand vacant place, how many do I need before the odds vs. a finess come into play?  I know that with AJxxx opposite the Kxxx its slight better to play for the drop, but what if I know 1 more vacant place, or two, or three?  When does it become time to finess.  Is there a table out there about these hands, the a suit combination, but with vacant spaces?

 

Others have posted calculators I guess, but you can also just do this by hand using the (x C y) stuff as above. (If you're unfamiliar with how this works, I can explain it more thoroughly.)

 

Hope this is useful,

Andy