TC: I noticed the bias too. Since it is quite hard for us, but very easy for Fencer to generate large statistics, I think it should be investigated asap. It is a potential exploit. For instance it makes 13/5 with an opening 62 much better than the usual 24/18 13/11 (until now I refrained from using that exploit).

My guess was that it had to do with the player at move winning or losing the opening roll in a multi-game match. But I didn't check that.

On a remotely related note, very long ago I submitted bug #1487 about a bias in the random placement in Logic, based on a statistic of 50x5 peg generations. I didn't even get an answer. I think that Fencer sometimes commits the fallacy of generalizing "some of my users are idiots" to "all my users are idiots".

playBunny: The reported order of the numbers within a roll isn't relevant is it?  Doesn't this just depend on whether a player swapped the numbers before using them?

I also checked my most recent two 21-pointers and found 6 out of 17 same initial rolls for both matches, so 35% compared with an expected percentage of less than 6% if they were independent.  I think this is statistically significant and wonder whether there is some circumstance where the first two dice rolls are determined at the same time (and so would always be the same), rather than when each player clicks on the game at different times?

grenv: Ok, but if you take out the doubles, there are only 30 possible rolls

But why do you take out the doubles? The second player can roll a double, so the second player has 36 different rolls. 2 of them can match the rolls of the first player.

grenv: Just checked my plakoto games from 2009. It's 10 cases of identical first rolls out of 27.

Another observation is that there are very few instances of both dice being different, e.g. 56, 43. I think the expected frequency of this would be 4 out of 9, but in the above sample it's only 5 out of 27. In playBunny's first sample, it is 0 out of 12. And in playBunny's second sample (the "reasonable" one), I count only 3 rolls out of 38 where both dice are apart.

Well... if I'm paranoid, at least I'm not the only one.

playBunny: oops, second roll can be doubles... gotta get some sleep.

Checking another two 21-pointers yielded a more reasonable number of equivalent rolls.

Game 1   35, 44
Game 2   52, 52
Game 3   54, 55
Game 4   53, 55
Game 5   64, 53
Game 6   32, 53
Game 7   51, 54
Game 8   23, 62
Game 9   42, 43
Game 10   41, 43
Game 11   31, 32
Game 12   61, 11
Game 13   46, 52
Game 14   62, 62
Game 15   63, 65
Game 16   13, 31
Game 17   65, 66
Game 18   65, 63
Game 19   35, 63

Game 1   34, 35
Game 2   54, 65
Game 3   45, 64
Game 4   51, 52
Game 5   14, 51
Game 6   14, 42
Game 7   61, 41
Game 8   16, 26
Game 9   23, 23
Game 10   13, 41
Game 11   35, 63
Game 12   52, 54
Game 13   42, 43
Game 14   25, 62
Game 15   65, 66
Game 16   63, 65
Game 17   65, 61
Game 18   32, 43
Game 19   34, 63

So the coincidences can be readily not found too.

pedestrian: I also did a very quick check using alanback's 21-pointer against furbster. It was the first and only match that I looked at.

Of the 12 games in the match, 5 started with the same roll for each player, although the order of the numbers was different in 3.

Game 1   61, 46
Game 2   23, 42
Game 3   12, 31
Game 4   14, 51
Game 5   13, 31
Game 6   45, 54
Game 7   15, 51
Game 8   41, 42
Game 9   41, 41
Game 10   13, 41
Game 11   65, 63
Game 12   31, 31

If it's coincidence then it certainly seems to be one that can be found without much effort.

ps. Abigail's right about the odds. It doesn't matter what the first roll is, the chances of the second matching it are dependant on the 36 possibilities for that second roll.

AbigailII: Ok, but if you take out the doubles, there are only 30 possible rolls I guess... right? so 1 in 15 then?

that makes sense... first die 2 in 6, second 1 in 5... 3x5 = 15

pgt: Of my current open backgammon games, 6 out of 10 had identical rolls for both players.

grenv: No, expected would be 1 in 18. The first player doesn't roll a double, which means that out of all the 36 possible rolls of the second player, only 2 match the roll of the first player.

pgt: Just to be clear... is the suspected behaviour that the first move for each player is the same? So if I roll a 3-1 so does my opponent?

If so I checked my last 7 games and didn't find it at all...

Expected would be 1 in 9?

pedestrian: I just did the same exercise on currently open games and 7 out of 15 had identical rolls for the first move

alanback: I just checked a small, random sample of games: the 13 games (or matches) of regular Backgammon played by alanback in 2009. Out of these 13, 6 games start with identical rolls by black and white.

I know, it's hardly conclusive. But still interesting.

The difficulty of writing code to deliberately skew the dice rolls is staggering. I cannot imagine it being done deliberately. This leaves open the possibility that there is some unanticipated factor that skews the randomness of the rolls. This also I consider unlikely, although I don't know precisely what random or pseudo-random number generator is used here. The fact is that out of hundreds of players, there will always be a few who are currently experiencing what appear in isolation as purposefully distorted results. This is just the result of the normal operation of the laws of chance. However, because only those few notice and report the apparent discrepancy, the anecdotal evidence always supports conspiracy theories. And backgammon players are always paranoid!

wetware: I've noticed this extremely too much this past 3 weeks.
the dice rolls that force me to leave men open, seem to coincide with my opponents rolling exactly what is needed to put me on the bar.
normally, I would take this with a grain of salt...but it happens so frequently lately,its become something I've been paying attention to.

Pedro Martínez:  I can't provide statistics, but my impression is that the bias is well worth investigating.  I think it happens often enough that some of the opening rolls should be played sub-optimally here.

I can only speak for myself, but no, I've got no statistics.

I wouldn't have suspected there could be such a problem, so I haven't especially been looking out for it. Even so, the tendency in my games has been obvious at times (several games in a row).

Now I learn that at least three other people have observed the exact same phenomenon. Sounds to me like it might be worth an investigation.

pedestrian: Can you publish statistics that prove that it isn't coincidence... or perhaps Fencer can?

Pedro Martínez: Definitely not a coincidence - if it's anything, it's a lot of coincidences!
I noticed it too.

Resher: I even reported it in the BugTracker. Fencer's reponse: “It is a coincidence.” *shrugs*

TC: I, too, have noticed that the first two rolls are the same much more often than I would expect.  And I don't think it's just me remembering these occasions that is distorting my perception.  Any other players noticed this?

As a backgammon player I fixed it: Since some months ago up today, in the first rolling of the players, always come same numbers. Like 5-1 vs 5-1, 4-3 vs. 4-3, 6-1 vs. 6-1, etc.

This is true fore most backgammon types (not for all).

I'm sure, most of backgammon players fixed this situation:

This is not a normal situation for randomized rolling computer dices.

Hope to hear for this matter..

Snoopy: ljubisa is a very patient player

i be very upset
Cloning Backgammon (Snoopy vs. ljubisa popovic)

i think its around move 50 my trouble started

spirit_66:   I suppose someone could create something for the "Zillions of Games" engine that would play Crowded.  From what I've seen, Zillions had backgammon, nack-, hyper-, and "deadgammon" (no idea what that is) capability.

coan.net:
I don't know!

spirit_66: Are there even programs out there that deal with the variant Crowded Backgammon? (don't need to post details if there are programs out there... just wouldn't think too many programs would be made for some of the rarer variants.)

pedestrian:
A program can give you the best moves!!!

skipinnz: Thanks for the advice. Actually, luck is what I used in this game where I was 'caught' as a 'cheater', so I guess it's not effective if you want to do it secretly. Apparently, he believed I was using a program. I don't understand how a program would help you be lucky...

pedestrian: The usual way to cheat is to bring along your own dice that are fixed, you could also bribe Fencer with lots os cash so the dice always fall in your favour, but as your a pawn I guess thats out, so I reckon you'll have to rely on good old fashioned luck. LOL

Does anyone know a way to cheat in crowded backgammon? I've just been accused of cheating, and if I'm going to be blamed for it, I want to have the pleasure of committing the crime as well.

gammonrace: I like the idea.
Boss?

can be played on a reduced board ... two home sections face each other (six points on each) and each player has 6 checkers placed like follow: 3 checkers on point 1, 2 checkers on point 2 and 1 checker on point 3 ... all backgammon rules are valid ... it's very compacted game, highly technical.
I can be played on one of the half of the board ...

Backgammon, 2200+, 7p & dc - 7 points match with doubling cube for 2200+, robin round

Karl

spirit_66: Somehow yes. But I personaly don't fight back the cheaters with their own weapons. I rather listen to the writing. Subtile though, even meaningless for the subject as it belongs to the social component. I leave the game checking to those who understand something about ;)

gogul:

----> <it's something for patient observation.>

Maybe with the help of a nice tool like GNU?

spirit_66: Turn-based gaming allows to moan over a long period of time. It's something for patient observation.

spirit_66: Ah, so turn-based backgammon just doesn't suit you. That's fair enough.

playBunny:

Well, I'm also registered at DailyGammon but I stopped playing there. There's also the long delay between the moves which can be used for foul play.

I prefer FIBS and GammonSite.

spirit_66: I'm still thinking more and more if BK is a good place for playing BG

BrainKing is great for a whole range of games but it's not the Home of Backgammon. If you're not already at DailyGammon you ought to check it out. See my profile for more details.

Heh heh, one of the attractions that I list is Pit yourself against a world class robot!

wetware: spirit_66 has said it too: Playing against bots I can do this on my PC with GNU, Jellyfish whatever for free.

The reason I asked you what you meant is that I think that argument rather misses the point. The point is that someone is masquerading bot as a person not that they are providing a bot to play against.

With regard to that latter point, whenever a site provides a bot to play against it is well attended! You may well have GnuBg at home but you cannot play turn-based against it with anything like the ease that you can at a site designed for the purpose. gb001, one of Dailygammon's GnuBg-based bots is very popular and not just with those who don't have GnuBg themselves. ;-)

wetware:

I can't see this problem as easy as you can. It drives me nuts thinking about that such a rotter is fooling me.

I pay at BK for playing BG against human beings. Playing against bots I can do this on my PC with GNU, Jellyfish whatever for free.

I'm still thinking more and more if BK is a good place for playing BG. The long possible delays between the moves are provoking any kind of fraud or foul play.

I've to face so often that somebody delay immediately the game if the one is on the loosing street. For me this is also a kind of foul play.

At the moment I think it's better to play BG with the short time limit of not more then 3 minutes.

Well, still frustrated about the way it goes here.

playBunny: In such cases, I hate the pretense and the unnecessary effort, pB.  Why should I have to go to the trouble of logging in, managing vacation days, and my remaining time, if my opponent is actually gnubg...which I could play at any time without those added steps?  And to think I may even have exchanged pleasantries with opponents who did little more than relay moves that were chosen by their program--well, I can't say it makes me furious, but I'm clearly not pleased by such actions.

I must say, however, that I haven't seen very much of that here.  I was mistaken when my earlier message said "...coming here to BK".  I ought to have corrected that.  Sure, there are problems here, but I've seen worse elsewhere--and that's what was on my mind when I wrote.

wetware: If I wanted to play against gnubg, I could do that without coming here to BK.

I've heard a number of people say something like this and, of course, I know what it literally means, but what is your point?

spirit_66: Its allright. The word you thrown at me made me laugh anyway, I think the laugh was on both sides. And about the cheats going on, I don't have the time for it. But what you observe might reinforce your oppinion on a suspected cheater but isn't enough for a proof IMO. In fact, players who like to concentrate on a move ge often run off in reallife playing, make forward boy backgammon is a fast game. Online playing allowes such a player to take his time, of course GNU comes after the game is finished. It happens that grandmasters exploit the idea to play with Gnu or fritz, it doesn't belong to bk IMO.

aaru: At some point, although absolute proof may still be out of reach, it is more reasonable to conclude that cheating has taken place.  On another site, I analyzed several players' matches.  In one case, I found at least 3 lengthy (21-point) matches where the player had 0 moves marked very bad, 0 moves marked bad, and just 1 marked doubtful--at gnubg's default settings.

If I wanted to play against gnubg, I could do that without coming here to BK.

gogul:

Ooohhh! Now comes the man from Switzerland with the big potatoes!!!

You can believe me that I'm only frustrated about .. let's say .. opponents with sound games.

Hard for me not to believe that there's something going wrong when I can watch them at the already opened game and it takes a long time till they make their moves. What do you think they are doing? My proof is if the GNU analyse at the end of the match show me no fault. The top of all is if they have very luck dices too.

But I never complained about any unfair play of you!!!

spirit_66: Your frustration because of cheaters, I don't buy it. Your offences toward me aimed on luck.