alanback: I agree and I think the doubles remove from the game well-played strategies. What has been the response to eliminating doubles in race games?

Groucho: I've never seen it adopted :) Some people probably like the added luck factor, consider it exciting.

alanback: It's only exciting when I roll the doubles. It's frustrating when my opponent does!

I actually think that doubles are an interesting addition to the positional evaluation that would be missed. They cannot be ignored since they occur 17% of the time. In a multi point match the luck usually evens out anyway.

grenv: I do not agree that luck usually evens out in the course of a match. It takes much longer, several matches at least. Certainly I have seen many 21 point matches dominated by luck, though hardly a majority of such matches.

Czuch Chuckers: not to mention the interest Fencer will get on the money already submitted

Antje:

playBunny: How could I resist the start date of Friday January 13

SueQ:
It all fit together so well i couldn't resist

volant: Lolol. Nice one!

volant: Thanks to you for putting on the prize tourney. Very nice of you ...YEAH! Volant... 3 cheers.

Down 6 to 5 in a 7 point cube match.... do I automatically offer a double?

Czuch Chuckers: Yes. What do you have to lose?

It almost seems like the person losing early on in a cube match has an advantage....

Czuch Chuckers: And if your opponent moved first with a 4-1 he should refuse the double.

If you moved first and this is your second move then he should refuse most of the time.

Czuch Chuckers: Losing early is an advantage? That is not true (obviously in my opinion) and can be proven mathematically. If you want to give me a headstart I'll attempt to prove it

so being up 6 to 5 you should be given a double offer and refuse it to knot the match?

Czuch Chuckers: It's obviously not true that the early loser has an advantage. I think that what you mean to say is that it's not as hard to catch up as it is to get ahead, and I think that is clearly true. Nor is that necessarily a bad thing.

Czuch Chuckers: See my earlier post as to when the leader should take or drop. In general, take if you are ahead in the current game, drop if you are behind.

alanback: But a person who has lost 5 in a row in a 6 game match, really only needs to win 3 games for the victory....

alanback: It's a good idea to read a book (or a chapter) on doubling strategy. Many of the answers to these questions are common sense once you think about them, but wouldn't be intuitively obvious to a beginner. A good example is the take/drop question. You know that the outcome of the match will be decided by the result of the current game if you take, and by the outcome of the next game if you drop. Your chances of winning the next game are 50-50 (modify this if you think you can estimate the relative skills of yourself and your opponent); you should take if your chances of winning the current game are more than that, drop if they are less.

alanback: Sorry... I think I will have to find my answers online somewhere. There must be a good doubleing strategy found online somewhere....

Czuch Chuckers: Depends upon when you are measuring the advantage. At the start of the game, it would be unfair to say "Player X needs 7 wins, Player Y only needs 4." However, once you make the assumption that one player is ahead 6-0, you aren't at the start of the match anymore. I don't care who the players are, I'd rather be ahead 6-0 than tied 0-0. At the start of the match, both players have an equal likelihood of getting to 6-0, so the rules don't favor either of them.

Czuch Chuckers: 4 games actually, you forgot about the crawford round.

And if you lost 5 in a row you probably lost the match already unless every game was worth a single point.

Czuch Chuckers: Because of the Crawford rule, after the leader gets one point away from the match, one game has to be played where the trailer hads no right to double. So at 5-0 the trailer needs four wins, not three.
As for doubling strategy, the case where the leader is one point away from the match is about the only simple one. That is what makes cubed backgammon great !

http://www.bkgm.com/articles/mpd.html

I know some of this is already covered, but my thoughts in my own words on the subject.

If your opponent only has 1 more point to win the match, then for you - it is beter to double early so the game with worth 2 points so if you do win, you will win twice as many points. (If you lose - well no mater if it is worth 1 or 2 points, you will lose the match.)

If your opponent only has 1 more point to win the match, and lets say you wait for a few moves into the game before you double - then your opponent has the basicly "free" oppertunity to either accept or deny the double and get to play again - and only giving you 1 point. That is your opponent only needs 1 point to win, and if he is already in a losing position, there is no point in him accepting a double - it is beter to just give you the point and start the next game. (Where as if you doubled early, he would already be in the losing game worth 2 points)

(This is of course after the Crawford match where 1 game is played without the cube)

BIG BAD WOLF: I think you got it!

Czuch Chuckers: Essentially the point about dropping when losing is a good one. It isn't always easy to tell of course :)

After one move apparently 4-1 is the only way someone playing first can actually be considered to be losing (on rollouts), hence my suggestion that you refuse the double if you played 4-1 and are immediately doubled. Some might argue 2-1 as well, but that works out to about 50-50.

grenv: I guess i dont understand why 4 1 is so bad? what about 3 2 then?

Czuch Chuckers: Well, it's just how the rollouts work.

with 3-2 the best move in a single point game (which is what the game in question is) is 24/21 13/11. This is not as bad as the best 4-1 (24/23 13/9) probably because the back checker is better situated on 21 and the checker on 9 can be hit more easily than on 11 where it is relatively safe and a good builder.

It's very marginal though, 3-2 isn't that good either.

grenv: Which rollouts are you talking about here? How many iterations and what's the error margin, etc, etc?

playBunny: Well I can't remember where I originally saw that, some book years ago.

I just looked them up at bkgm.com. Apparently they use 46,656 iterations (seems like a funny number) and assumes cubeless play for a frame (which is essentially what we were talking about). There are probably more accurate rollouts available but they seem pretty good.

They say:
4-1 = 49.8%
2-1 = 49.9%
6-4 = 49.9%

Important to note that 6-4 has many gammon wins compared to gammon losses so is usually a better roll, but if gammons are not important as in the last frame then it's a bad roll.

Best roll in all cases is 3-1 obviously.

Also even 4-1 is winning if gammons are taken into account. Moving first gives you an advantage in most cases.

grenv: I'm off to bed so just a quickie..

46656 / 36 = 1296 and 1296 / 36 = 36. Such a number ensures that each dice roll is represented fairly for the first three moves.

I've done rollouts to 1296 and to 12960. Similar principle; 10 goes each for each pair of opening rolls in the latter case.

The 1296s were just so many wasted CPU cycles. Even at 12960, though, the expected error value exceeded the difference between the top moves in many cases. Getting the error values small enough to reliably decide between two moves would require rollouts of 500,000 and more.

I agree with 3-1, and 6-1's up there too. Whether the results can reliably differentiate between the least popular rolls I'm not sure. I'll have a look at what I found in a few hours...

playBunny: hmm, I thought the rollouts were essentially random, so the number of iterations being a multiple of 36 seems a little arbitrary. However if the first 3 moves are selected, rather than random, then it makes sense.

4-2 comes out better than 6-1 according to the site, but it's close.

grenv:
There are probably more accurate rollouts available but they seem pretty good.

They say:
4-1 = 49.8%
2-1 = 49.9%
6-4 = 49.9%

Do you mean that if I'm from 1 point of winning (for example 6-0 in a 7 point match), I should drop the cube if my chances on that game is 49,8%? That would mean that if I'm on the losing side, I should wait until my chances are 50,2% and not to double before that. That happens almost in every game, and thus I would get one point after another until the game would be even.

Or is the situation different in games when the losing player are not as close as 2 points away?

Wil: If you are 1 away from winning and your opponent is 2-away, you should drop any double when your chance of winning the current game is below 50%. The same is generally true in any case where your opponent is an even number of points away. If your opponent is an odd number of points away, then you should take any double unless you are seriously concerned about being gammoned.

Again, the percentages should be modified if you think you know you are better than your opponent or he is better than you.

alanback: Thanks for clarifying, I was sure we were talking about a 6-5 game from the start, but that was a while ago. :)

Also, you don't get to 50.2% on every game, you could be losing from the start and never come back. Also, how would you know that the chance was 50.2% without a computer? The first move is easy since these roll outs are well enough known.

grenv: That's where experience comes in :-) It's a good reason to double early, before the position becomes complex.

alanback: That's not what I meant. I am very aware of the strategic considerations of the cube, having learned to use it about 30 years ago, but most of us can't calculate the winning %ages accurately enough to determine the difference between 49.8 and 50.2 without a computer. And it won't always happen that you get into a position that is obviously a winning one.

aha! I'm here!!!!

Can someone tell me if there is something I am missing here or a rule I dont know about
In my game: http://brainking.com/en/ShowGame?g=1214077
I cant move the black piece at 11 in to the 6 position.. any reason why?

Rose: Because then you wouldn't be able to use the one on the other die.

Rose: You must move 11 to 10, and then 6 to 1
This is part of the new rules recently implemented - correctly - that you MUST move both pieces if you are able to. And unfortunately for you, if you move 11 to 6, you could not use your 1-spot!

pgt: ahhhh I got you.

Thanks folks for the quick replies!

is this really the best backgammon player? As far as I can tell he is on top of the ratings without making a move.

http://brainking.com/en/Profile?u=4320&eg=23&p=1

grenv: Looks like a fix

grenv: Highest rated? Jah. Best player? Pah!

Fencer: Could you make it so that provisional games cannot be played in private, please? There's no way for us to check for cheats otherwise.

playBunny: I was being ironic, I knew it was a cheat. Each game is 3 moves or fewer.

I don't think any games should be private personally. What have people got to hide?