Pedro Martínez: Great machine, and here was i thinking they paid 1000 people to sit at their cubes and roll dice!

If there is a defect it would seem not to be the random number generator but that the code doesn't use the generator in the particular case mentioned, but instead just gets the last number... sounds like a caching problem?
I wonder if those games were played with 2 people on the same computer? moves happening very quickly? We need more of this type of data most likely, in order to replicate the problem.

moistfinger: However, it is quite surprising because BK uses a very sophisticated system to generate the dice. :)
http://www.youtube.com/watch?v=7n8LNxGbZbs

Pedro Martínez: Well, that explains my searches not finding it. :)
It was closed in 2008... i'd say it should be re-opened and investigated. I'm sure anyone with access to the historical database could publish the statistics for a start.

wetware: The dice is a total joke on this website. It just doesn't feel right. I have never been one to whinge about backgammon dice before playing on Brainking. I know it is supposed to be random but it just isn't, it is skewed.

grenv: It was. In Czech though.
http://brainking.com/cz/ReadBug?bgi=1754

pedestrian: Was this added to the bug tracker? If so I couldn't find it.

pedestrian: Whatever the reason, somebody has screwed up!

grenv: We can only speculate about the cause of the problem, since we didn't write the code.

If we are to speculate, one possible hypothesis could be that some unintended event prevents the dice from being generated in the normal way. Whenever this event happens, you get the same dice as the previous roll. When it doesn't happen, you get a random roll. We must assume that this hypothetical event would be something that happens at the second player's first roll - but again, this observation is only useful to someone who has access to the code.

As an aside, if this hypothesis is correct, the event seems to happen in roughly 1 out of 3 games.

Thom27: That's a wierd bug... increasing the odds of the second roll equaling the first? What kind of twisted algorithm would cause that?..?..

Unless you wrote code that generated a random number first, then used that to determine whether to roll or just use the first result, ... but why write that sort of code?? It just doesn't seem like a plausible defect.

Any ideas?

Thom27: I agree, and have spent an inordinate amount of time analyzing results here.  (I wish it were easier to do, or that the flaw was ALWAYS evident, or the underlying pattern easier to discern.)  I'll continue playing less and less here, until it's remedied.  (I want to spend more time playing and studying--not investigating an unusual system flaw.)  I'm generally an outspoken skeptic of various "dice cheating" claims, but what's happening here is too much of an outlier to be dismissed cavalierly.

I also tried (unsuccessfully) to identify WHEN this skewness began.  I hoped that by doing so, I might help the powers-that-be to identify some code or procedural change that might have triggered it.

pedestrian: This is well possible, I must only download more files. I'm working on it...

I'm also going to do a chi-square test, which calculates a probability for an event to occur by coincidence, under the assumption that the dice are ok (equally distributed and independent).

Thom27: That's a great initiative! It seems clear that it is actually a bug and should be repaired as soon as possible. I wonder if it would be possible for your program to analyze a larger sample of games?

Thom27: “Coincidence.” Fencer, 4 December 2008, 09:33:00 CET

TC: I also had the impression that equality of first and second roll occurs much too often.

(For this topic, see the posts starting 3. Nov. 2009)

To check this, I downloaded the MAT files of all Backgammon games I have played so far, and wrote a programm which counts the games where the first rolls of both players are equal. Result:

206 games total
79 of them have equal first and second rolls (38.3 %)

This is 6.9 times the expected value (5.556 %).

Universal Eyes: this happened to me recently here. he 6-6 two in a row to beat me when i was way ahead! i was PEEEVED! i could not believe it.

A monthly series of fast-paced Hypergammon tourneys.


I like it fast, 5-point Hyper, 1st May 2010

I like it fast, 5-point Hyper, 1st June 2010

At the beginning of every game, the initial position is determined randomly. The pieces are set up symmetric like in usual backgammon, i.e. if white has n pieces on point x, then black has n pieces on point 25-x.

Besides from this, there can be various detailed rules to set up the pieces. The following is an example:

There is no blot (single stone on a point). every player has 15 pieces like in normal Backgammon. Every player has at least 2 stones in every quarter of the board. The rearmost stones of a player are not passed by any opponent's stones (i.e. if the white rearmost stones are on point 4, then there are no black on points 1 to 3).

All other rules are the same as in standard Backgammon.

alanback: There's quit a few that just take the gamble in an even game, that you will not accept a double and forget that the next roll could be double 6's and they could and usually do get counter doubled.
Then there looking at losing 4 instead of sneaking one.

Thad: It does if he has a mathematical chance to win, and it is a very good reason to double. I was speaking of situations where the opponent has no chance to win, but for one reason or another chooses not to resign.

Doesn't doubling when you're ahead and a move or two away from the end of a close game help to keep your opponent from getting a lucky win with doubles, which increases the skill factor in the game and reduce the luck factor?

Nothingness: The entire purpose of the doubling cube is to force the opponent to up the stakes or lose. In a face-to-face game, players will not usually play a game to an end when the outcome is a foregone conclusion. Online, someone has to double or resign to make that happen. Given the pace of play here, some folks like to move things along as quickly as possible.

AbigailII: It saved a bit of clicks.
Be aware of your doubles though, because you can score gammon or backgammon. If an opponent is about to be gammoned, it's bad to force double, he rejects and you only recieve 1 point instead of 2.

Nothingness: So, you're one move away from checkmate, and you double the stakes. Your opponent resigns instead of accepting the double. Didn't really change the outcome, did it?

Nothingness: The point you may be missing is that you only resign the current game, not the entire match. In your example, resigning would mean that you only lead by 4-1 instead of 4-0. Accepting would mean that the current game counts for two.

this seems flawed. How can you force a person to either up the stakes or lose..? I'm assuming that this is not an official rule. it would be like being one move away from chekcmate and saying i want to double the match.

Nothingness: the short answer is no. they can however force you to choose between resigning or doubling the value of that game, it's your choice but you do have to choose.
At the bottom of the page of this link http://brainking.com/en/GameRules?tp=23 is a more detailed explination

I am unfamiliar with how the doubling cube works. i was in game with a person and i was up 4-0 and during the beginning of the 5th game my opp send a message requesting to double the gmae. i had two options to either accept the double or to resign the game.. can you force a person to resign while using the doubling cube?

Pedro Martínez: LOL, I decided not to play any more tournament but that one had me really tempted !

What about a Logik tournament with compulsory random placement (see bug 1487) ? Brainking, the site with Easter-egg game variants.

Pedro Martínez: Awwww!!

playBunny: I am afraid Fencer has just fixed it. We're playing an unrated game of Fevga with alexlee and I can't do it any more…

Pedro Martínez: Lol. That sounds like fun!

Pedro Martínez: lol, awesome :D

A monthly series of fast-paced Hypergammon tourneys.


I like it fast, 5-point Hyper, 1st Apr 2010

I like it fast, 5-point Hyper, 1st May 2010

sal cine vrea sa joace

A monthly series of fast-paced Hypergammon tourneys.


I like it fast, 5-point Hyper, 1st Mar 2010

I like it fast, 5-point Hyper, 1st Apr 2010

Snoopy: A slow coach can block a country road but it takes two of them to block a two-lane highway.

alanback: ah yes i got accused of holding that tournament up way back in June 2007
funny how the section i was in finished long long ago..lol

WASSAIL

Wassail started just before Christmas in 2006 with 109 players in 22 sections. There are still 6 unfinished sections in round 1. With a minimum of 26 players advancing to round 2 and a max section size of 5, we are guaranteed at least six sections, meaning that there will be at least 2 sections in round 3 -- with luck round 4 will be the final. I estimate this will finish somewhere around 2020.

grenv: Great idea. I have made an appointment with my lawyer and will do the update on Thursday morning.

grenv:

The tournaments of the fathers shall be visited upon their children, unto the seventh generation!

pgt: There should be a way of passing your current tournaments in your will... could end up having your grandkids finish the tournament for you. Maybe someone not even born yet will play the winning move years from now. :)

AbigailII: My last move in this tournament was in March 2006. I am collecting a pension now. In those days I could afford to be a Brain Rook. I might not even be able to afford an internet connection by the time this tournament is over (lucky I have been eliminated already)

grenv: They have played 120 moves a year, but they are with two, so that makes 240 moves in the games. 48 moves a year is almost one per week, throw in some vacation days and the calculation is correct.


Oh my, it's so ridiculous ;)

grenv: Oh, it's not just anti-backgammon. That tournament has dozens and dozens of unfinished games, all-most all of them involving one of the players of the game I posted a link to.

AbigailII: yeah, and i notice it's also 120 moves, but only one game... glad i didn't enter an anti-bg tournament.

Czuch: There's also this one. Started a year later (Oct 2006), but it's the first game in a 3 win match.

Czuch: they have played about 120 moves in 5 years... that works out to 24 moves a year, which is about a move every 2 weeks... unfathomable - almost impossible given the 7 day limit.. they literally have to almost wait until the last second on every move!