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Hand dealt vs. computer generated

#21 User is offline   barmar 

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Posted 2016-August-29, 08:28

View Posthrothgar, on 2016-August-28, 06:41, said:

When I say "plausibly insecure" I mean that someone could invest a relatively small amount of money, crack the ACBL's hand generator, and use the first hand of a tournament to predict all subsequent hands in real time.

You mean the first day of an NABC they can predict all the hands for the rest of the week? Wouldn't that require them to use the same run for all sessions during the tournament, and in a predictable order?

Or just that from first board of a session they can predict the remaining hands of the session? But unless they can get the first hand ahead of time, does that do them much good? And if they can get the first hand record, they could probably get the hands for the entire session. I suppose someone could play board 1, go to the restroom, enter the board in their phone and get the rest of them -- is that the concern? In any "important" event (like the late rounds of big events like Spingold), players aren't allowed to leave the playing area unsupervised.

#22 User is offline   661_Pete 

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Posted 2016-August-29, 10:37

I'm wondering, what's the freakiest hand ever seen on BBO (outside of the goulash's, that is)? I think the longest suit I've ever had is a 9-carder - I have a vague recollection of an 11-1-1-0 in live bridge many years ago (missing the AQ of my long suit, I couldn't even make game.....) but it's all rather hazy.
A few weeks ago on BBO, my partner picked up a 7-6-0-0 which is quite a rarity I think.
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#23 User is offline   Stefan_O 

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Posted 2016-August-29, 14:17

View Post661_Pete, on 2016-August-29, 10:37, said:

I'm wondering, what's the freakiest hand ever seen on BBO (outside of the goulash's, that is)? I think the longest suit I've ever had is a 9-carder - I have a vague recollection of an 11-1-1-0 in live bridge many years ago (missing the AQ of my long suit, I couldn't even make game.....) but it's all rather hazy.
A few weeks ago on BBO, my partner picked up a 7-6-0-0 which is quite a rarity I think.



I had 7-6 around the 20th of June this year:

http://tinyurl.com/z36qqum
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Only a few days later, the robot got its revenge :D :D (I havent seen anything like it, since)

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#24 User is offline   hrothgar 

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Posted 2016-August-29, 15:01

Here's an amusing hand from yesterday's BBF event

{comments}


(Still somewhat surprised Barry didn't raise to 6)
Alderaan delenda est
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#25 User is offline   661_Pete 

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Posted 2016-August-30, 02:31

View PostStefan_O, on 2016-August-29, 14:17, said:

Only a few days later, the robot got its revenge :D :D (I havent seen anything like it, since)
I think you can blame your robotic partner there, for not leading their ("its"?) singleton spade and at least hold opponents to ten tricks. Especially at MPs scoring.

I've never tried playing with robots on BBO and I don't have any intention to. Robotic dealers I can live with, but robotic players...... :blink:
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#26 User is offline   Fluffy 

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Posted 2016-August-30, 02:46

It depends on the club, at my club with 85 average age, they shuffle once the deck. This results on balanced hands for everyone*

Have you ever heard an old player something like...

-I have to rebid my suit, I have 5!

That's because 5-card is a rare feature when you don't shuffle enough.


*Just to explain, when you draw trumps or run a suit, you place same suit cards one after the other, that's the usual way of playing a hand. On a properly shuffled deck, if you pick a card, chances of next card to be the same suit ar 23.5%. Just after playing the hand however chances are around 60%, and after shuffling badly they will be 35-40%. This results on balanced hands all around.
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#27 User is offline   Fluffy 

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Posted 2016-August-30, 02:51

I met a clever lady who explained to me Why AQ finesses were usually not working, because people with KQ lead king then play queen, putting the king over the queen in general.
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#28 User is offline   Stefan_O 

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Posted 2016-August-30, 08:07

View Post661_Pete, on 2016-August-30, 02:31, said:

I've never tried playing with robots on BBO and I don't have any intention to. Robotic dealers I can live with, but robotic players......


OK -- if you only play with your fixed/known partners, that's the best, of course.

Otherwise, I can only recommend the "Robot Duplicate" tourneys.

Even though "surprises" happen once in a while,
-- the robots IMO make a MUCH, MUCH better & sensible game than playing random human pickup pards online,
esp. after some practice, as you get used to deal with some of the robot peculiarities.
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#29 User is offline   nullve 

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Posted 2016-August-30, 08:42

View Postpigpenz, on 2016-August-28, 18:21, said:

A lot of Barry Crane's rules for playing suits was based on old fashioned shuffling from what I have read

View PostFluffy, on 2016-August-30, 02:51, said:

I met a clever lady who explained to me Why AQ finesses were usually not working, because people with KQ lead king then play queen, putting the king over the queen in general.

Barry Crane's rule for finding queens and jacks.
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#30 User is offline   1eyedjack 

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Posted 2016-August-30, 14:24

View Post661_Pete, on 2016-August-30, 02:31, said:

I've never tried playing with robots on BBO and I don't have any intention to. Robotic dealers I can live with, but robotic players...... :blink:

Your loss. But your choice.
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.

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#31 User is offline   hrothgar 

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Posted 2016-August-30, 14:57

View Postbarmar, on 2016-August-29, 08:28, said:

You mean the first day of an NABC they can predict all the hands for the rest of the week? Wouldn't that require them to use the same run for all sessions during the tournament, and in a predictable order?

Or just that from first board of a session they can predict the remaining hands of the session? But unless they can get the first hand ahead of time, does that do them much good? And if they can get the first hand record, they could probably get the hands for the entire session. I suppose someone could play board 1, go to the restroom, enter the board in their phone and get the rest of them -- is that the concern? In any "important" event (like the late rounds of big events like Spingold), players aren't allowed to leave the playing area unsupervised.


Comment 1: Looks as if someone has operationalized the attack

Comment 2: You don't need the first hand for the session, you can move forward or backwards
Alderaan delenda est
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#32 User is offline   Vampyr 

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Posted 2016-August-30, 20:20

I thought it was by now well known that you can sufficiently randomise an unsorted deck with just 7 riffle shuffles, or 2500 overhand shuffles.
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#33 User is offline   mikestar13 

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Posted 2016-August-30, 20:25

View Posthrothgar, on 2016-August-28, 06:41, said:

FWIW, I spent far to much time looking into the intricacies of the system that the ACBL and the USBF use to generate hands.

Executive summary: The system that the ACBL uses to generate hands is both plausibly insecure and statistically problematic.

When I say "plausibly insecure" I mean that someone could invest a relatively small amount of money, crack the ACBL's hand generator, and use the first hand of a tournament to predict all subsequent hands in real time.

When I say "statically flawed" I mean that the linear-congruential generator that the ACBL uses to generate pseudo random numbers only covers a relatively small portion of the space of hand deals and the process that the generator uses to walk through this space use a very simple process. If the phase of the hand generator program were to align with the phase of the the lcg all sorts of bad things would happen.

At the most basic level, and lcg is not cryptographically secure and should not be used for any kind of statistical simulation....



My God, I knew ACBL could be stupid, but a lcg? I knew this algorithm was s*** in first week of programming school back in the 70's.
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#34 User is offline   cynac 

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Posted 2016-September-01, 17:20

I agree with the first post. That hands have become "more distributional". And I agree with the "myth" that it is because of previous imperfect shuffling. For rubber bridge it would take an enormous time shuffling to get rid if the increased linkage in suited cards, resulting in a more even distribution if they are then dealt around the table.
In duplicate, there is indeed, as mentioned above, an increased sequence of tricks played in the same suit.....you pull trumps....you run suits. When did you last play suits at random?

As an extra "myth", there was a suggestion, perhaps true, that finesses are more likely to fail in hand-dealt rubber bridge.... Because there is the small extra chance that the finesse has already been taken. (Basically the most likely card to be played after a jack is the queen.....and the two might not be split during the shuffle). If you ever did magic with cards, you'll have realised how easy it is NOT to change the order.
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#35 User is offline   ShirleyMqz 

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Posted 2017-March-20, 23:24

View PostPhil, on 2016-August-27, 21:17, said:

When others have looked at this topic, imperfect shuffles by players actually generate wilder hands than computer generated hands so the whole
'computer-hands' thing is a myth generated by club players.


The consensus is that this is not true. Hand shuffling actually generates MILDER hands than true random shuffling. People complain that the computer hands have more singletons and voids, and there appears to be some truth to that.

Another accusation is that computer hands violate the "law of symmetry" that hand-shuffled cards seem to follow, which says that if your own hand is flat then the other hands are more likely to be flat, and if your hand is wildly distributional then the other hands are likely to be as well. In other words, if your hand is 4-3-3-3 it's unlikely that anybody has a void, even more than normal statistics would indicate, and similarly if you have a void it's likely that nobody holds a 4-3-3-3 hand. Computer hands, being truly random, don't behave that way.
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#36 User is offline   pigpenz 

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Posted 2017-March-21, 17:45

View Postnullve, on 2016-August-30, 08:42, said:


As I started to read this thread I was wondering the same question. Barry played minor suite finesses a different way
which supposedly his ideas came from the fact of incomplete shuffling.

also I thought I had always read that shuffling around 7 times takes care of incomplete shuffling.
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#37 User is offline   JLilly 

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Posted 2017-March-22, 19:01

View Postpigpenz, on 2017-March-21, 17:45, said:

As I started to read this thread I was wondering the same question. Barry played minor suite finesses a different way
which supposedly his ideas came from the fact of incomplete shuffling.

also I thought I had always read that shuffling around 7 times takes care of incomplete shuffling.


Riffle shuffling seven times randomizes all but the top and bottom two or three cards. Assuming the riffle-shuffling is competent and sincere.
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#38 User is offline   JLilly 

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Posted 2017-March-22, 19:06

View PostJLilly, on 2017-March-22, 19:01, said:

Riffle shuffling seven times randomizes all but the top and bottom two or three cards. Assuming the riffle-shuffling is competent and sincere.


My personal position is that every club game whose rake is independent of the deal should practice memoryless deals. That is, if you're not playing against the house at all, and the house takes a fixed cut from the players' play, then the deal should not be able to be gamed.
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#39 User is offline   barmar 

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Posted Yesterday, 15:21

View PostJLilly, on 2017-March-22, 19:01, said:

Riffle shuffling seven times randomizes all but the top and bottom two or three cards. Assuming the riffle-shuffling is competent and sincere.

I'm a pretty poor riffle shuffler. When I'm shuffling, I do the follow procedure:

Take a hand from the board, do a quick overhand shuffle of it.
Take another hand, overhand shuffle it.
Riffle these two hands together.

Repeat the above for the other two hands.

Riffle those two half decks together, and then do several more riffle and overhand shuffles of the whole deck.

I hope that the shuffles of the smaller portions of the deck make up for how clumpy my riffles are when I shuffle the whole deck. And throwing in a few overhand shuffles ensures that I don't have the same top and bottom cards each time I riffle.

Blackjack dealers in casinos use a similar procedure of shuffling small parts of the deck first and then merging them, that's where I got the idea.

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