Minitinous Trump Break

[Davekapiti]

Time for the System Programmers to review, and hopefully modify, their dealing algorithm. Over the past 9 weeks I have become frustrated with the monotonous,unfair distribution of trumps, repeatedly 4 -0 or 5-0 breaks making the contract impossible to make, despite having 26 -29 HCP. Between dumy and declarer there are 8 or 9 trumps but the contract is impossible to make .

 

I have been playing Bridge competitively for over 40 years and I have never experienced this type of trump distribution over such a continuous period of time. Occasionally bad distribution as mentioned above can be a challenge, but the current situation is beciming quite boring t the point of expecting it each time a game in a suit has been bid correctly.

 

Comments from other players are welcome.

[manudude03]

It would help if you were to provide actual numbers. What I will say though it that people in real life are terrible at shuffling and so computer dealt hands will often appear to be more distributional than normal.

[eagles123]

I have to say playing with the robots I do feel at times that things aren't random, and cards are programmed to split badly/finesses to fail etc. sometimes u have hand after hand with 5-0 splits and three finesses failing every hand and after a while it can get quite tiresome!!

[barmar]

Every few months someone complains that our dealing algorithm is unfair. And every time, I explain that we've analyzed them and not found any deviation from the expected randomness. We also had the author of BigDeal, generally considered the authority on random dealing, analyze our data, and he said it was OK.

[HardVector]

The only time this comes up for me, is when I am practicing with my partner and I am fixing specific parameters for our hands. I notice the other hands tend to be statistically skewed in generating extreme breaks. When we put no constraints on, however, things look fine.

[johnu]

You must be just a general BBO member/player. Bad breaks and offside honors are skewed to the run of the mill players. If you have a Platinum Executive membership, finesses work at least 75% of the time, and you never get contract breaking bad breaks unless you are late with your monthly dues.

[smerriman]

A 4-0 trump break should happen once every 10 hands. Look at the last 100 times you've held 9 trumps, and count how many 4-0 splits there have been. I suspect it will be pretty close to 10, and you're simply imagining things like everyone else who brought this up.

[dsLawsd]

I would be interested in seeing the kernal/speculum/ or other tool myself together with an analysis. Over time it is likely to be fine, but the times that strange things do happen seems to be in certain events suggesting that hands with very even distribution are thrown out by non random methods. But then we Engineers/math guns are always a suspicious lot.))

[thepossum]

Please disregard any reputation points I gave above. I tried to undo one that I believe was incorrect.

 

I agree in principle with what most people are saying but the issue is far too complex to address on a forum and I'm too tired

 

Suffice to say I trust that the hands are suitably random, whatever randomness means :)

[nekthen]

Humans are programmed to see patterns. We see representations of things in clouds and on toast. Our brains organise random occurrences into patterns and we cannot stop them doing that. We just have to recognise that this bias exists

[barmar]

I would be interested in seeing the kernal/speculum/ or other tool myself together with an analysis. Over time it is likely to be fine, but the times that strange things do happen seems to be in certain events suggesting that hands with very even distribution are thrown out by non random methods. But then we Engineers/math guns are always a suspicious lot.))

The only non-random thing we do is swap the hand with the most HCP to South when you play Best Hand robot tourneys.

 

We also use the Linux rand() function, which is admittedly not the best random number generator. But Hans's analysis didn't find any particular bias due to this.

[dsLawsd]

Second opinions anyone? Statistics profs?

Also, swapping the hand violates the Laws of Bridge which states what is required for a bridge hand deal. What should/could be done instead is to Rotate the best hand to South without changing anything else.

 

The story continues - What deal generator does the ACBL use for Tournament play?

[pescetom]

Also, swapping the hand violates the Laws of Bridge which states what is required for a bridge hand deal. What should/could be done instead is to Rotate the best hand to South without changing anything else.

Good point.

 

The story continues - What deal generator does the ACBL use for Tournament play?

Good question.

[elwood913]

I’ve never seen patterns in toast?! Does this mean I’m not human :(

[barmar]

Second opinions anyone? Statistics profs?

Also, swapping the hand violates the Laws of Bridge which states what is required for a bridge hand deal. What should/could be done instead is to Rotate the best hand to South without changing anything else.

How can you rotate the best hand to South without changing any of the other hands? And what difference does it make how we get the best hand into the South position, it has the same effect on the randomness.

The story continues - What deal generator does the ACBL use for Tournament play?

We use a simple C function we wrote decades ago.

[cholula]

fwiw... I feel the same way... I alter my play in robot tournaments to expect finesses to be off. I find that to be more annoying than bad trump breaks which seem to be more randomly distributed.

[pescetom]

How can you rotate the best hand to South without changing any of the other hands? And what difference does it make how we get the best hand into the South position, it has the same effect on the randomness.

 

We use a simple C function we wrote decades ago.

By elementary logic you can rotate the best hand to South, the other hands rotate too. And this maintains the same random deal whereas the BBO method does not.

 

And I at least assumed the question about ACBL was related to real world tournaments, not BBO.

Our RA uses Big Deal I think.

[smerriman]

By elementary logic you can rotate the best hand to South, the other hands rotate too. And this maintains the same random deal whereas the BBO method does not.

This can't make a single bit of difference. The probability a given deal occurs is identical whether you rotate or swap.

[Lorneg]

It's not as random as you think. Just keep track of the leads for a while. It is probably

less than 2 or 3% of the time that the opening lead is away from a King. Now later on

in the play you get the Bots leading from Kings.

When I play in the club you just learn who leads form Kings and who doesn't There it

is at least 30 or 40% leading from a missing king.

[JmBrPotter]

. . .

 

The story continues - What deal generator does the ACBL use for Tournament play?

 

The ACBL began using Big Deal for the Winter NABC in 2016. Nicolas Hammond (author of the recent Detecting Cheating in Bridge) proved that feeding a suitable program boards 1, 2, & 3 of an ACBL generated board set would yield boards 4-36 in a short enough time for the result to be useful for cheating on most of the "solved" boards. He also delivered statistics indicating that some pairs might be using this "crack" (or one like it) to cheat at NABCs and Regionals. The ACBL (and EBU, and USBF, and WBF) finished switching to Big Deal by January 2017.

 

Apparently, most folks with sufficient knowledge of bridge, national bridge organizations, cryptography, mathematics, and statistics (This skill cluster probably requires a team of several folks in most instances.) believe that with suitable communications security Big Deal is not subject to such a "crack."

[JmBrPotter]

. . . I have been playing Bridge competitively for over 40 years and I have never experienced this type of trump distribution over such a continuous period of time. Occasionally bad distribution as mentioned above can be a challenge, but the current situation is becoming quite boring t the point of expecting it each time a game in a suit has been bid correctly. . . .

 

Dave,

 

If the powers behind Big Deal say that BBO has a good hand generator, I strongly trust that BBO has a good hand generator. The authors behind that generator have excellent knowledge of both the math behind good generators and the statistics to validate them. That theory knowledge has excellent backing by good computer programming to turn the theory into practice.

 

I have a very minor philosophical quibble with Big Deal. It samples the population of all possible bridge hands without replacement (Big Deal would deal every possible bridge hand exactly once before it repeated a hand (perhaps, a desirable property if you want to be certain that the hands for your tournament will have no duplicates). Philosophically, I feel that the sampling should be conducted with replacement (There is a tiny chance {several orders of magnitude larger than Planck's constant but still quite small} that a set of a few thousand hands for a large tournament would contain one or more duplicates.) The practical difference is that once in several human lifetimes we are very unlikely to see a headline about two identical hands at the same tournament versus never seeing two identical hands at the same tournament. That is, no practical difference.

 

You may have built a "feel" for what "random" bridge hands should resemble from playing shuffle and play events (e.g., local club games, KO teams, and Swiss teams). To get genuinely random hands via shuffle and play, every hand would need to be shuffled seven or more times. How likely is that? What proportion of the hands will be shuffled one or two (at best three) times before dealing? Inadequate shuffling will skew the hand distribution towards deals with four balanced hands each with 8-12 HCP (e.g., lots of 3-2, 2-2, and 3-1 trump splits and way to few 4-0, 4-1, and 5-0 trump splits). Players who encounter randomly distributed hands when they leave the sheltered waters of their local shuffle and play club for the first time will have their instincts for how the cards should break thoroughly battered.

[JmBrPotter]

. . . Suffice to say I trust that the hands are suitably random, whatever randomness means :)

 

Possum,

 

To a statistician, "randomness" means something like, "The statistical properties of an observation are indistinguishable from the statistical properties of a random sampling (e.g., tosses of fair coins, rolls of fair dice, or clicks from a Geiger counter) with a distribution matching the claimed distribution of the afore mentioned observation."

 

That definition probably sounds very precise and quite sensible. Yet, a statistics professor could probably speed a full semester long advanced graduate level course on the topic (and wish for a second semester). Donald E. Knuth devotes Chapter 3 (nearly 180 pages) of his The Art of Computer Programming to the topic of generating pseudo random variants and validating their "randomness" by that definition. It is a suitable text for a one semester undergraduate class on the topic and barely scratches the surface.

[tomkron]

We also use the Linux rand() function, which is admittedly not the best random number generator.

 

Actually, it's a terrible random number generator, even if you are using excellent seeding. (How are you seeding it?) The version of rand() on my Linux box has a period of at most 34,359,738,352 (~2**35) per the man page which means it can produce only an infinitesimal fraction of the 53,644,737,765,488,792,839,237,440,000 (~2**96) possible bridge deals. That tiny fraction might be representative of deals in general, but maybe the people doing the complaining are in fact observing patterns which weren't checked for by your statistical analysis.

 

Why can't you use a better random number generator, perhaps Mersenne Twister? It has a period of roughly 2**19937. Or get 96 bits of entropy from a hardware RNG or /dev/random or a cryptographically-secure RNG and use them to select a deal from the space of all possible deals? Several web sites (I believe Thomas Andrew's and separately Richard Pavlicek's) contain descriptions of how to do this.

[pescetom]

This can't make a single bit of difference. The probability a given deal occurs is identical whether you rotate or swap.

I'm no statistician and would be happy to hear from someone who is, but your argument doesn't convince me: the probability of a given deal is identical to that of any other deal, but that does not mean that any set of deals is equally random however the hands were generated.

[barmar]

It's not as random as you think. Just keep track of the leads for a while. It is probably

less than 2 or 3% of the time that the opening lead is away from a King. Now later on

in the play you get the Bots leading from Kings.

When I play in the club you just learn who leads form Kings and who doesn't There it

is at least 30 or 40% leading from a missing king.

I don't think that's because the deals are less random, it's because of GIB's algorithm for selecting opening leads. It tends to avoid leading away from kings much more than humans do.