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

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.

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.

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

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.

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.

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?

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".

21 : 13/11 6/5
31 : 8/5 6/5
41 : 13/9 8/7
51 : 13/8 6/5
61 : 13/7 8/7
32 : 13/11 8/5
42 : 8/4 6/4
52 : 13/8 6/4
62 : 13/5
43 : 13/10 13/9
53 : 13/5
63 : 8/5 8/2
54 : 13/4
64 : 24/14
65 : 24/13

My propositions. I didn't check with a bot and I could be wrong about some.This of course would be with 100% of same rolls. Some of them are too bold to be played against only 50% of same rolls.

Resher: If both numbers were generated at the same time, wouldn't you expect 100%..? To what do we attribute what is being seen.

Some kinda fun #2
One big section, 5 points match with dc, fischer clock: 2/0.18/5
Everyone is welcome!

See you across the board,
Karol

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playBunny: The links take me to the log in page.

Carl, AlliumCepa: That's wierd. I copied the links directly from the tournaments page. I've changed them from absolute urls to relative ones. It should be fine now. Thanks, guys. :-)

Look the position Fevga (Jaak vs. AlterMann) , please!
All black checkers are blocked, but they are not collected onto the one point behind player's prime. Thus BrainKing Fevga rules http://brainking.com/en/GameRules?tp=111 don´t require to unblock a point in the prime to allow the opponent a chance to move. I used this possibility and moved
41. 18-23, 18-23, 17-22, 19-24
Backgammon Galore has the same rules http://www.bkgm.com/variants/Fevga.html but there is a reference of George Savdar http://www.bkgm.com/rgb/rgb.cgi?view+1202 that there are many different variations in Greece.
The main variation has a rule:
If you have a 6-prime and the opponent can't move at any dice (for example has all his checkers behind this prime (not the only case), you MUST free one point in your turn in order the opponent to have non-zero probability to move.
So, according to this rule I did an illegale move. Where is the truth?

Jaak: I recently read that rule somewhere as well, and noticed we did not have that here. I just assumed maybe there are more than one version of "Fevga"

I had been curious, because GoldToken just added a game VERY similar to Fevga, but it's called "Moultezim". With that game the tiny difference between it and what we have here is that you can not fill more than 4 pips in your opponent's starting area. (Fevga is 5 pieces in your own starting area) PLUS it had the rule you mention, for Fevga.

Just noticed this one.....

The first doubling cube tournament

Started in 2005, and still not out of the first round???????

Baked alaska and cardinal.... 5 years for a 7 point doubling cube match???? Really???? Come on guys, that is just plain wrong

Czuch: Holy crap! You're not kidding. It's why I didn't join it when it was announced.

playBunny:   Fully deserving of a Super Snail achievement award.

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!

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

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

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.

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 ;)

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)

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. :)

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

grenv:

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

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.

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

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

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sal cine vrea sa joace

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Pedro Martínez: lol, awesome :D

Pedro Martínez: Lol. That sounds like fun!

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: Awwww!!

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.

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?

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

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 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.

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?

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.