Vikings: If that proved to be too much information, the point in question could just be shown as guarded without giving the number of pieces on it.

I would still like to try the game first with it showing all the pieces on a point if the dice would let you move there even if the point is guarded. There would still be plenty of darkness in such a game. Too much darkness and it'd just turn into a running lucky game. I don't know if it'd work or not. Too much information and it'd be very much like regular Backgammon, that I agree with.

Let's pretend it's the start of the game and I roll 5-3.Even before this roll I know the four points where all of your pieces are and how many are on them even though I cannot see any of your pieces. This is analogous to the start of a Dark Chess game. I can see my four points and the rest of the table would be dark. Now the roll of 5-3 would show me your two runners on my 1 point, the 3 point, the 5 point, the 16 point(Your outer table 9 point), your 5 pieces on your 6 point, and your 4 point.

Whatever move I decide to make will be unknown to you until you roll the dice. Now this is where how the game would be played will make a difference. Will the game show my dice roll or not? If it doesn't show the roll, then you'll always be in the dark except for those cases of when your next roll happens to reveal where I might have moved from an earlier position. If it does show the roll, then you'll have information about where I might have moved, but you won't necessarily know where I moved.

As the game progresses, they'll be an increase in information as the pieces become spread out and some rolls would reveal a lot of the table. And then, just like Dark Chess, it would get real dark as the last of the pieces passed each other and it became a running game. I can imagine other scenarios, such as me having five or six points guarded in a row. No matter what roll I received it would show up a lot of points in front of this and be very dark behind it. When both people have all the pieces in their home bases it would be a very dark board. Here again, the information shown would make a difference. Are born off pieces shown? I think they should be, but it could work without showing them too. This is sometihing I don't like about how Dark Chess is on this site as compared to IYT version, the promoting of Pawns and showing them and the piece promoted to. BrainKing reveals nothing about this happening. IYT, will either take the piece out of the opponent's captured pieces bag, or in the case of an extra Queen or third Rook, Knight, or Bishop, will show that an extra piece is on the board though it doesn't reveal its position. Both ways are playable, but it makes a difference in the play at times.

on this move i rolled 2+4 ... should i have moved 5 to 1 and 3 to 1 (leaving a single piece on 3) or was i allowed to move 5 to 3 and then 3 off the board ?

in the second option i only used 5 of the possible 8 steps (which i would have used in total in the first option)

is this allowed ? (or is it just as much frowned upon as on using only 1 die when you can use 2 dice as well)

Hrqls: You may do either move as you see fit. Nothing compells you to be efficient in the usage of the pips or in baring pieces off. Perfectly fair and part of the strategy of the game. Especially if your opponent has pieces in your home base.

Another example similiar to this is when your opponent has a piece on the bar and you're bearing off. Say you have two pieces on your 2 point and one on your 1 point and no others and roll 6-1. You have some choices here. You could bare off two pieces on the 2 and 1 point leaving one piece on the 1 point. Better is to move one piece from the 2 point to the 1 point and bare off the other piece on the 2 point.

The rules that I've read of Backgammon say moving the pieces around in your home base instead of baring off is allowed and they also say you needn't use the most pips possible. This is different than the maximum usage of the dice because you have used both dice.

Hrqls: You are required to use the dice to tha maximum but not necessarily the pips, so what you did is perfectly legitimate and the best move.

Walter Montego & playBunny: ah thanks, i am glad :) *phew*

i move both dice when i can (even if its to my disadvantage) but i didnt think about this possibility until after i moved

It used to be when I played someone a game of Backgammon and we were within a few hundred points of each other in rating we'd be playing for 8 rating points. Now there's this sliding scale and I find it completely unfair to the higher rated player. I will never be able to play a higher rated player that cares about his rating on this site because how disadvantageous the odds are now. Someone that's 300 points above me risks 14 rating points to my 2! This is nowhere near the odds of my actual chance of winning. It may not 1 to 1, but it can't be 7 to 1.

Can we please have a ratings system for Backgammon that reflects the odds of winning and keeps in mind that there's luck involved? This disparity will further segegrate the Backgammon playing community or will encourage people to not play rated games at all. I can see having a big difference in the points awarded if we were playing a match to 10 wins or game points, but to have it like this for a single game is ridiculous.

Walter Montego: Actually the ratings system is now correct, assuming a game of skill of course. This will end up being fairer in backgammon as well, but still not optimal, once the ratings are recalculated.

It makes complete sense that the player rated higher risks more, and if that doesn't reflect the actual odds, then the difference in ratings is too much. This will probably be fixed somewhat when the recalc happens.

grenv: If a recalculation of everyone's rating takes place, it won't fix anything. It will just use this rating system retroactively. I agree that a higher rated player should get less reward for winning a game against a lower rated player, but the points should be based on the ratings of the players involved and their actual odds of winning a single game. For a series of games it should break even after awhile if the odds are calculated correctly. For a match where the points are awarded at the end of a series of games, I can see having it set up with higher points, but this would again be because of the odds. In a long match, the better player will win more often.

Walter Montego: I agree with Walter that the differential between winning and losing appears to be overstated -- the new system is better than the old one which effectively didn't recognize ratings differences at all (unless you were playing outside the 400-point band on either side of your own rating), but I think it represents an over-correction. I think we should give the new system a chance to operate before making judgments about it. We are used to playing under the old (flawed) rules; now we high-rated players are going to have to work hard to maintain our positions. I have suffered, too, because the change in the system coincided with something of a slump in my games; still I notice that those behind me are also suffering a decline. I expect a significant compression of the ratings spread, and I think that is a good thing. Why shouldn't we have a system under which a player can reasonably expect to climb into the upper echelons in a relatively short period of time? I think it should make the site more competitive and interesting.

alanback: I think you're right about the compression. In fact, because the points awarded favour the lower player so greatly, I believe it'll be over-compressed.

Playing all and sundry in single-pointer tourney matches is going to kill the ratings of the higher players who join a lot of them. (Score one for the Knights vs the Rooks, for a change, lol). Winning 60-65% of tourney matches, as a top player would, will not be enough compensation for the 7 to 1 points differential against players within 300 points and certainly not for the 15 : 1 against those further down.

After the adjustment all those games which previously won 8 useful points will only, in fact, have earned beans while the lost matches will be harshly felt.

Another aspect of this formula is that the ranking system will be highly volatile. A player rated 120 below will have a 2 : 1 advantage in the points awarded though the skill differential is minor and the luck differential is zero. Any player to reach a height can be tumbled merely by winning 50-50 against weaker players.

I took my thinking about this a bit further but posted it to the main BrainKing board where arpa raised the issue.

It's serious: This change will have a severe flattening effect. If left alone we will all - high and low - eventually have the same rating!

http://brainking.com/en/Board?bc=1&bscx=403725

(Bear in mind that the link puts my message at the top of the page but doesn't show anything posted afterwards. There may well be replies to it on the "previous" pages.]

playBunny: We won't all have the same rating, since if you lose and your rating goes down, you will gain more next time you win. Since there is some skill in the game the list will still be meaningful, though not as much as another system may be.

In fact winning 65% of games against average players is the problem, and there are undoubtedly players with inflated ratings as a result (for all I know I may be one :)

grenv: In any event, because Fencer is recalculating the ratings from the beginning, we will be able to tell tomorrow whether we all wind up with the same rating!

grenv: We'd eventually have the same rating.

The formula will consistently pull the higher rated player down by more than they can possibly win because it doesn't account for luck.

So the lower rated player will go up by more than they should and the higher player down until the two have the same rating.

Apply that to all possible pairs and everyone has the same rating!

playBunny: That doesn't make sense, there must be a point at which equilibrium is reached where players of different ability reach different ratings.

For instance if I win 62.5% of the time against a weaker opponent, we would balance out at a point where I stand to gain 6 and lose 10, whatever that difference is.

I agree in principle that this system is not good for backgammon, but the ratings would not balance to everyone equal since there is some skill in the game.

grenv: The following is from US Chess ratings

In any good rating system, if two players with the same rating played a large number of games, one would expect each to win half of the games that were not a draw. As the difference in their ratings increases, the probability that the higher-rated player will win increases. In the U. S. system the difference in ratings at which the better player will win 90.9% of the time is arbitrarily set at 400. A player with a rating of 1100 will win 91% of his games with a player with a rating of 700, and a player with a rating of 2000 will win 91% of her games with a player with a rating of 1600.

For any particular match, it should be possible to calculate from the difference in the player's ratings the probability that one of the players will win. Taking “We” to be the “win expectancy” and “ΔR” the difference in the players' ratings,

We (underdog) = 1 / (1 + 10 ^ (ΔR / 400))
[The formula on the original web page is incorrectly formatted. The one above is correct. ^ is raise-to-the-power-of]

For example, using this formula, if two players differ by, say 90 rating points, the probability of a win for the higher-rated player is 0.627, and for the lower-rated player, 0.373. If the results of a series of games bear out this expectation, the players' ratings are “correct,” and shouldn't change. Players' ratings change only when the results of a match are not what the difference in their ratings led one to expect, and the extent of the change in ratings is based on how far off the expectation was.

So, according to the US Chess formula, the 63% point is a difference of 90 points.

In Backgammon 65% is the difference between a top player and an average player. I believe BKR formula is based on the the one referred to above so we could expect the entire ratings spread to be maybe 100 or so points each side of average!

So, okay, you're right - a difference of zero is exaggerated but with such a small spread and a volatility of up to 10% of that per match? ... they might as well be the same, lol.

I can't wait to see the results of the recalc....

FIBS rating - good for backgammon - http://www.fibs.com/ratings.html

And a good calculator once you get past airplane-cockpit syndrome, lol.

Javascript calaculation:
function afRatingChanges (fRatingP1, fRatingP2, uiExperienceP1, uiExperienceP2, uiMatchLength)
    {
    var fRatingDiff = Math.abs (fRatingP1 - fRatingP2);
    var fRootMatchLen = Math.sqrt (uiMatchLength);
    var fBasicMatchValue = 4 * fRootMatchLen;

    var fProbUnderdogWins = 1 / (1 + Math.pow (10, fRatingDiff * fRootMatchLen / 2000));

    if (fRatingP1 < fRatingP2)
{
     fProbWinsP1 = fProbUnderdogWins;
     fProbWinsP2 = 1 - fProbWinsP1;
     }
    else
   {
  fProbWinsP2 = fProbUnderdogWins;
    fProbWinsP1 = 1 - fProbWinsP2;
  }

    var fExperienceFactor1 = Math.max (1, 5 - (uiExperienceP1 + uiMatchLength) / 100); // Will be 1 when
    var fExperienceFactor2 = Math.max (1, 5 - (uiExperienceP2 + uiMatchLength) / 100); // Exp >= 400.

    var fRatingChange1W = fBasicMatchValue * fProbWinsP2 * fExperienceFactor1;
    var fRatingChange1L = fBasicMatchValue * fProbWinsP1 * fExperienceFactor1;
    var fRatingChange2W = fBasicMatchValue * fProbWinsP1 * fExperienceFactor2;
    var fRatingChange2L = fBasicMatchValue * fProbWinsP2 * fExperienceFactor2;

    return new Array (
       fRatingChange1W, fRatingChange1L,
      fRatingChange2W, fRatingChange2L);
    }

It doesn't seem to be possible to create a tournament of multiple-point matches. That is, one in which each player would play the other a 3-point match, for example. Am I missing something?

I've no idea, but I hope so! Sounds like a very sensible tourney to me. ;-)

Brainking board's perhaps best for this as someone might have done it for a different game type.

I am new on this site and I would like to play backgammon but it seems to me that it is not possible to use the cube.
Is this well that?
If so, do you know why this possibility does not exist here?

jolat: Indeed, there's no cube on this site. The reason is that it isn't implemented - a Fencer decision. ;-) At some, yet unknown, time in the future, a backgammon version with a cube will be implemented.

Some put a line on top of this page with the message that cubes will be implemented in the future.

What is that "cube" and "bug" all about?

I've just added these two points to the rules:

• If it is possible, both dice must be used. It means that some pieces can become "frozen" in certain positions because making a move with these pieces would create a situation where the second dice couldn't be used.
• If only one die can be used, the one with the higher number must be chosen.

Please let me know if it really works. I hope I've fixed this issue at last but I could easily overlook some special cases :-)

Fencer: Thank you, Fencer. I interpret this to say you have changed the software, not just the published rules?

alanback: Right, I changed/fixed the model.

Fencer: Ah, good. I presume that the new rule is in effect immediately even for running games? Or do running games keep using the old rules, which didn't enforce maximum die usage?

AbigailII: It's in effect immediately even for running games. It would be too complicated to separate them.

Marfitalu: Looks like the system currently does not see that you can bear off chips soon, and in the process - trying to make you use both your dice.

Looks like Fencer will have to add the code of "if using the smaller dice leads to a point where you can start to bear pieces off the board, then allow it - otherwise ...."

BIG BAD WOLF: I've run into several situations where it won't let me use the smaller die first. These aren't games where I will only use one die, but want to move the smaller number first, to set up the larger number. In one case it didn't give me the option of swapping my dice. Is this a bug or have the rules changed?

UzzyLady: If it is as you describe it is definitely a bug.

UzzyLady: If you see them, post about it here - a link to the game, and what you want to do...... That way Fencer can see it and fix it.

http://brainking.com/en/ShowGame?g=1084875 and
http://brainking.com/en/ShowGame?g=1084875 are examples of the bearing off problems. In both cases I want to take the smaller die first so that I can start bearing off.

And of course, now that I'm looking for it, I can't find the other game I had a problem with. I'll keep searching.

http://brainking.com/en/ShowGame?g=1090894&i=18

I wanted to swap the dice so I could take the 4 first, but there was no swap dice button.

Not uncommon, but it needs to be fixed!

alanback: I'll gladly suffer through the fixing of a few bugs, if it means we get the big one taken care of!

I'm not sure which big one you are referring to, but I can't say the present situation is an improvement if the reports below are accurate.

UzzyLady: I believe Fencer will fix this relatively trivial bug [pointing and shaking index finger at Fencer!] as soon as he is made aware of it :)

WhiteTower: I'm sure you're right :-)

alanback: I mean, he obviously worked in the shadows while we were all jeering at him, and now his surprise has come out slightly faulty :) SURELY his pride will not allow this issue to remain alive for much longer ;)

i have another game with the same bug : http://brainking.com/nl/ShowGame?g=1084960

i want to move the 4 first, so i can bear off with the 6

Hrqls: i posted the bug in the bug tracker

Wait a minute.

Whoah, real-time troubleshooting ;-)

Fencer: ah! i checked for you but didnt see you online .. i guess you heard all our souls cry for help ;)

Mine work as well. Thank you.

Should be fixed.

Fencer: Hats off to you, you must be quite a programmer!

alanback: He sure is - who knows ONE perfect programmer who doesn't introduce a new bug fixing a old one? ;)

Fabien Letouzey! Perhaps it surpasses the "King" Richard Lang.......