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.

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?

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.

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.

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.

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

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.

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 %).

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

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?

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: 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.

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?

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.

pedestrian: Whatever the reason, somebody has screwed up!

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

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

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.

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.

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: 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.

Meanwhile I have downloaded more games:

630 games total
218 games with equal starting rolls (34.6 %)


All games in the sample are played between Summer 2009 and today.

Games in 2009:

306 total
99 with equal start rolls (32.4 %)

Games in 2010:

324 total
119 with equal start rolls (36.7 %)

A chi-square test is almost pointless; obviously this is almost impossible to happen just by coincidence, if the probability of equal start rolls is 1/18 = 5.556 %. But I have done it anyway.

Every one of the n = 630 games falls in one of two classes:
class 1: first and second roll equal (expected probability p1 = 1/18)
class 2: first and second roll not equal (p2 = 17/18)

Y1 = 218 is the number of games in class 1.
Y2 = 412 the games in class 2.

now is calculated:
V = (Y1 - n * p1)^2 / (n * p1) + (Y2 - n * p2)^2 / (n * p2)
= (218 - 35)^2 / 35 + (412 - 595)^2 / 595
= 1013.1

If the dice were not biased (probabilities p1 and p2 as expected), then the value V would be lower than 6.635 with probability 99 %, and lower than 10.84 with probability 99.9 %.

(edit:) see this table for the values to compare V with. With 2 classes one must look in the line with DF=1 (degrees of freedom).

moistfinger: Your credibility is already suspect when you say you never whined before -- all real backgammon players whine about the dice ;-)

alanback:
Point taken.

Pedro Martínez:
LOL

could anyone explain cloning backgammon for me? the rules are a bit confusing. they way it seems to be worded i could feesably end up with an infinite amount of pieces to bear of my bar. if i keep catpturing my enemys pieces i have to bear off more and more pieces.

Nothingness: I think you'll find the stratergy is that if you hit your oppnent then you will gain an extra man, therefore you have to way up the concequences of taking men off.

Nothingness: they way it seems to be worded i could feesably end up with an infinite amount of pieces to bear of my bar.

No, that would require an infinite amount of moves. But you're always complaining your opponents move only a few times a month, so while the number of pieces on your bar may grow, you don't live old enough to get an infinite amount. Now in theory, the maximum number of pieces on the bar is unbounded.

Nothingness:I think that 503 was my highest pip count ever:  Cloning Backgammon (Peter 63 vs. wetware)

wetware: Pip count 521 - 340.

AbigailII: I think you should get achievement points for that!    :-)

AbigailII: Life's too short to drink bad wine or play cloning backgammon!

AbigailII:His opponents do not have infinite Vacation Days,so his Days on the bar can be much shorter then anticipated.

still going after nearly six years wow

Neznalek's private tournament in Gammon Race #12

AlliumCepa: Thanks Ivaylo.

Where does the link with "web" take you?

A monthly series of fast-paced Hypergammon tourneys.


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

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

what is the record for the most amount of consecutive passes?

AlliumCepa: Thanks for that. Interesting, it's the right page but you're not logged in!

It should be okay from now on. I've been doing each month by editing the previous month's post and copying it into a new one. For some reason that gives me a fully-specified url (http://web.brainking.com/en/Tourneys/...) instead of the relative one (Tourneys/...). I'll make sure that I delete the unwanted portion in future.

i have passed 32 turns in a row

AlliumCepa: I am not sure if the "web" part should be there at all.

That's what I have in my address bar and it works for me, so it's legitimate. I just took the web. bit out and that worked too, except that I wasn't logged in. I'm not sure when or why Fencer created the web subdomain but, whenever it was, I updated my home page, which has links to login me in directly. It's been like that ever since.

AlliumCepa: I don't think it's a "bad" for anyone, lol. In any case, I've changed my home page link to log me in without using the web subdoimain.

Nothingness: I sure hope you're using autopass! ;-)

nabla:  I almost feel dirty playing an opening 21$ here.  It's like stealing equity.  (I normally play it anyway, but here it's a gift.)

Quick movers Random tourney.

Random game tourney with 2 backgammon variants