Pedro Martínez: ah ok, thanks :)

i will use the cube more often then i guess :)

Pedro Martínez: actually I have gotten many gammons with a double and received 4 points, I have also gotten backgammons with a double but also received 4 points, I just assumed that I had gotten the checkers out and had them sent back

Vikings: Would you please provide a link to any game like that? Plz

I'll look

Pedro Martínez: my bad, it looks like they were all resignations, but here is a link to where I received 4 points but may have been eligible to receive 6 http://brainking.com/en/ArchivedGame?g=1177229

Vikings: Yes, you should've gotten 6 points. I don't play "cubed" anti-backgammon because of this bug right now, since it is a major flaw, in my opinion.

Pedro Martínez: as I said earlier, I may have had all the checkers out of the 1st quadrant at one time or another and had them set back, I have had that happen in hyper-backgammon and only received 2 points also

Pedro & Vikings: in this game my opponent resigned but i only got 1 point for the game

(my opponent knew i would get 3 points if he resigned, he wondered about the 1 point as well)

how come vikings game gave him gammon points upon resigning of his opponent ? (although it should have been a backgammon?) while my game doesnt ?

does anyone have any idea about the way this bug works ?

Hrqls: don't know, looks similar enough to my game

In Vikings game, they got 4 points since the cube was doubled and the person who resigned did not have any pieces off the board.

In Hrqls game - only 1 point since the person who resigned already had a piece off the board.

WHAT NEEDS TO HAPPEN (in my opinion): With Anti Backgammon

Lets say someone moves all their pieces off the board - it needs to look at how many points they would get if it was regular backgammon, then just give those points to the opponent with pieces still on the board.

Lets say someone resigns. First the computer needs to "pretend" that the person that resigned has won the game (of regular backgammon), and calculate how many points they would get if they actually moved all their pieces off the board. (regular, gammon, backgammon) - then give those points to the opponent with pieces still on the board.

Pedro Martínez: I´m on his enemies list for more than ayear, just because I won 2 games in a row...

It´s not my fault that he is such an awful player. I tried not to win, but he played so badly that I had no alternative but win...

He is a really sportsman... LOL

Hrqls: It's exactly as BBW said - in anti games, the system takes the position of the loser's pieces into consideration when counting how many points the winner will get. And it should be the winner's pieces that must matter.

André: The interesting thing is that he has added me to his enemies list but hasn't declined my invitation yet. He probably waits for me to go to vacation or something and then, when he sees I haven't logged on for some time, accepts the invite...yeah, that's what I call sportsmanship

Pedro Martínez: why don;'t u canccel the invite then?

furbster: I want him to accept it. I don't plan to go anywhere in the nearest future. If I do, I'll cancel it, of course...:)

BIG BAD WOLF: ah! thanks! indeed the difference is the number of pieces which are beared off already .. i didnt notice that :)

i agree completely with you .. now we just need to bribe/blackmail fencer ;)
does anyone knows what he wants for christmas present ? ;)

Hrqls: BrainKing membership

wellywales: he wants to be a rook ?
hmm i can imagine .. it must be boring and lonely to be the only white king ;)

i am trying to learn how to use the cube better

i am wondering though .. i declined the cube action in this game ... i didnt think i could win this game (too many safe options and some steps ahead of me) .. accepting would mean this game makes the match .. but declining means i have to win the crawford game first, and then another game to win the match ... i am not sure if i have a better chance winning the next 2 games than i would have had to win the doubled game (which i declined)

any opinions ?
(i think its ok to talk about this cube action as it has been handled already ? if not, please let me know and i will remove this question :))

the player results in the cubed teamtournament counts all games separately. should it count all matches for this individual result ?

Hrqls: Very close call.

Your chance of winning from 19-20 down is about 28% (2 in a row is obviously 25%, but you have to factor in the chance of getting a gammon in the next game).

Your chance of winning this game is probably about 28% as well (or thereabouts), so not much you could do to improve your odds (except for hoping he doesn't double!)

Maybe someone could run it through a computer and give us the results? I think it's ok since the double is already rejected.

Hrqls: The tournament is still decided by the won total match, and not each game - I kind of like how it shows for the players stats each game

grenv: *nod* i had a bad feeling about that game .. i cant count chances yet though so i didnt have a clue about 'about 28%' :)

she is a good player, at least our games seem to be about even ... so its tough :)

(btw i wont tell her you called her him ;))

BIG BAD WOLF: true ... but declining a cube action will cost you a game while it can win you the match

Hrqls: agreed, the games won/lost is kind of irrelevant. Maybe showing both matches and games would be interesting, but matches is what should be there. I guess it's the default behaviour of the programming rather than intentional.

grenv: *nod* i think so as well

Hrqls: Looking at the position you've got two men back versus Gamek's single man which ready to escape. If it doesn't manage to escape, (eg a 2-1) then you've got to hit it and cover the blot on your 4-point. You've got no home development and only the initial builder's points while Gamek has her bar point and three sources of builder. Both your back men are blocked on 6s and 5s. And the pipcount deficit is 20 points plus the roll. Not a lot of joy in that scenario. ;-)

grenv: Nicely judged.


Cube analysis, cubeful equities:

3-ply
W 73.2%, Wg 18.5%, Wbg 0.6%, L 26.8%, Lg 5.0%, Lbg 0.1%

1. Double, pass _______ +1.000
2. Double, take _______ +1.238   (+0.238)
3. No double __________ +0.978   (-0.022)
Proper cube action: Double, pass


Rollout, 1296 games
W 72.8%, Wg 29.3%, Wbg 2.6%, L 27.2% Lg 6.4%, Lbg 0.5%

1. Double, pass _______ +1.000
2. Double, take _______ +1.217   (+0.217)
3. No double __________ +0.964   (-0.036)
Proper cube action: Double, pass

The figure in bold is how much would have been given away by taking the cube. A value of .200+ makes it a major blunder.

playBunny: *phew* so i did the right thing (according to the rollout) .. but considered (a tiny bit) a major blunder ;)

her builders made me worry ... if she wouldnt have had those then i would have probably accepted .. although i guess it still wouldnt have been the right thing to do :)

Hrqls: Heh heh. I considered a "tiny bit" too. As always, it's much easier to find justifications for an answer that has been proved. Such was the case with the description of the position. ;-)

Aye, such a nice set of builders was a big threat.

playBunny: This case seems like a good "exercise" for cube newbies (cewbies?) or judgement evaluations ;)

WhiteTower: *nod* thats why i posted it ... being a newbie at this myself as well :)

btw i just won the crawford game, so far the cube declining was ok ... now we are up to the final game :) we will have fun :)

playBunny: I'm surprised it was a major blunder, what is the chance of winning the game from that position? It must be significantly 28% for it to be a blunder. What do the numbers actually mean from a statistical perspective?

grenv: i always though 25% chance to win was enough to accept a double ?

lately i am forcing myself to play more defensive though .. i have lost too many points by accepting too much so far :)

Hrqls: That's the pure mathematical cutoff, however you do gain a slight advantage in accepting so the real number is often slightly less (depending on the match score).

In this case the 28% is your chance of winning the match after rejecting the double. In this case, because accepting basically makes this game the final one, 28% becomes the cutoff.

It seems that the chance of winning this game turned out to be 26.8% or 27.2%, so to say that it would have been a major blunder is a little harsh (unless I am missing something).

grenv, Hqrls I won't claim to be an expert in this area so here's what I understand myself.

W 72.8%, Wg 29.3%, Wbg 2.6%, L 27.2% Lg 6.4%, Lbg 0.5%

Wins (all), Wins by gammon, Wins by backgammon, Losses ditto
The percentages are for the person cubing.
(That's why I said "nicely judged" to you grenv because Hrqls' chaces were 27.2%)

1. Double, pass _______ +1.000
2. Double, take _______ +1.217 (+0.217)
3. No double __________ +0.964 (-0.036)

The equity figures are how many points you'd gain or lose on average. Drop the cube and you'll lose every match 1.000. Fail to double now and you'll only win .964, ie. delaying for 1 roll will cost 3.6% of the possible points (because of losing the game or the next one or from subsequent cube decisions). If the opponent takes the cube then the gain will be .217 above expectation. That's a huge increase, and a huge additional loss for the loser given that they could have dropped and only lost the single point.

The 75%/25% double and take rule works because it's the break-even point for the taker. if they play 4 nmatches and take, then losing 75% at 2 will cost 6 points but they'll win 2 back with the other 25% for a net loss of 4. That's the same as if they had dropped the cube in all four games.

That rule doesn't take into account the gammon and backgammon wins which, in this example, are considerable. Two men on the wrong side of a 3-prime with good builders. That's the extra factor that makes it such a blunder. The maths now becomes
(72.8 - 29.3 - 2.6 = 40.9) x 2 win points +
(29.3 - 2.6% = 26.7) x 4 gammon points +
2.6 x 8 backgammmon points
versus
27.2 x 2 lost points.

As far as knowing exactly how the equity figure is worked out I can't say. In a single game it's as straightforward as the maths for the 75%/25% example shown but for longer matches I believe the equity value also has the future matches factored in through the use of the match equity table. That's where I get uncertain because to it seems logical that equity for a match can only go as high as 1. Perhaps Alan can explain this aspect.

- side note -

For anyone else who is between 92-100% confused with all the percentages being thrown out - you are not alone. Maybe if I took a some time to really read what is all being said it might make me a beter player - but I have a simple test - if I think I still have a good chance to win - accept double. If I think I have a good chance to lose - deny the double. Depending on how many points are left - how close the match is can help determin if I want to take bigger chances or not.

Ok, just wanted to get that off my chest. Carry on with all the percentage talk... :-)

http://xfriis.dk/maxfriis/bg/double.html

BIG BAD WOLF: "If I think I have a good chance to lose - deny the double"

Aye, that's a reasonable guideline to use at the start but you'll be at the mercy of those who know they can scare you by doubling. There are plenty of situations that look like you're going to lose when you should actually take. You'll know you're getting the hang of the cube when you confidently take what you would once have dropped.

Paradoxically a common feature in games with those who don't know how to judge the cube is for them to take a cube that should be dropped like a hot rivet. And when they get the 6-6, or whatever, and go on to win... Doh!

playBunny: I think, therefore, that on balance you should never accept the double in that game because of the great chance of being gammoned.

In this case though, the gammon was irrelevant since the match would have been over anyway on a loss, and all that you need to consider is the win/loss %ages. These may be tainted by not playing for a gammon, so I suspect that the actual chances are slightly lower than 27% and the rejection of the double is correct, but not by much!!

grenv: That's a very good point and suggests that I made a mistake in setting up the analysis. I'll do it again....

But no. At a score of 2-away, 2-away, whether in a 2-point match or the 21-pointer that it was, the number and conclusion are the same: -0.238 (3-ply) and a very bad take.

Hmmmm......

Doh! It's in what Hrqls said in the original query, "i am not sure if i have a better chance winning the next 2 games than i would have had to win the doubled game (which i declined)". The answer is a resounding Yes to trying to win the next two games rather than that single one.

I normally use the equity figures when analysing but GnuBg can alternatively show the equivalent in Match Winning Chance and it's much better for this query.

Cube analysis, 3-ply, MWC

1. Double, pass _____ 68.75%
2. Double, take _____ 73.20%  (+4.45%)
3. No double ________ 68.33%  (-0.42%)

Proper cube action: Double, pass

This time you can see that taking the cube gives away 4.45% more than playing the next two games.

playBunny: hmmm, I think I was mistaken with my 28% comment. After looking up match equity tables it seems most do say low 30s, which means the action is clear. I need to memorize them better. :)

grenv: Then someone like Ed Trice will come along and patent a new version of Backgammon where memorizing equity tables (as per chess openings) will be impossible or impractical ... hence my dislike of cube games :)

frolind: great site! thanks!

thanks to all for the analysis .... it helps me a lot to decide on future cases ... although i will need to practice these theories, and what i think to understand from it :), a lot more :)

knowing your opponent is a good advantage on cube decisions .. some players accept too many cube actions, some players can be scared easily ... and some players know how to advantage of your mistakes :)

Here is another game.
Dont look at the way it finishes (although me telling you this gives it away i guess :))

if it was a cubed game and he would have doubled i would have declined the double directly!

but ... does anyone have time and is willing to do an analysis of this game if the cube was used ?
please ? ;)

Hrqls: I'm happy to analyse a position or match every now and then if it helps someone learn something.

What do you mean by a cube analysis given that this is a single game? In order to analyse it I need to know how long the match is and what each player's score is at the start of the game. Also to know at what moves any cube decisions are supposed to have happened.

playBunny: ah ok .. suppose its a 21 point match, and its the first game of the match ... to keep it as clean as possible with all options still open

Hrqls: And the cube... What do you want to know?

playBunny: if he would have offered a double ... i would have declined ... but .. how much of a blunder would it have been to accept ?

what were the chances to win a game like that ?

this might be quite useful information for future games .. although these situations dont happen too often (in my games yet) .. i might go for them more often if the chances are higher than i thought them to be :)

Hrqls: Lol. Aye, but when? If he'd doubled on his first move you'd have been a fool to drop! And what situation are you talking about? There are 94 "situations" in that game. ;-)

playBunny: move 35 (where the link leads to :)) .. or maybe 1 move earlier

Hrqls: Lol. My eyes are closing. I thought the game had ended with a resignation at that point.

If I were white I would expect my opponent to gratefully drop the cube if it were offered. The hit is only going to happen 30% of the time and the chances of keeping the blot thereafter are not high enough to justify taking. You were very lucky.

Thus says me. Let's see whether GnuBg is going to agree or tell me off!

....

Okay. After White's move 34, and just before Black's 1-1, the percentages are W 91.1%, Wg 55.3%, Wbg 0.1. After the 1-1 and Black has closed his home table, they are W 93.9%, Wg 75.6, Wbg 4.4%

Dice decisions.
Double: Are you crazy???? Gammon, man, go for the sizzle!!!
Take: Are you crazy???? The frying pan's out and hot! And you want a doubled cube???