cube action in an seemingly harmless position - Backgammon Forum - Discuss Backgammon Strategy, Clubs and Books

Two Plus Two Forums Sports and Games Chess and Other Board Games Backgammon Forum hosted by Bill Robertie.

cube action in an seemingly harmless position

Post Reply Subscribe

...

07-25-2013 , 07:02 AM

colin20g

enthusiast

Join Date: Nov 2012 Posts: 88

Code:

GnuBG ID: hfPgATCwz+BBCA:cAmgACAACAAA
XGID=-b---BE-B---dD---dAc--Aaa-:0:0:1:00:1:2:0:5:8

Black on roll: What is the correct cube decision for both players?

Spoiler:

Quote

07-25-2013 , 08:47 AM

911InsideJob

enthusiast

Join Date: Oct 2012 Posts: 52

Double / Pass.

This one is strictly score based. At 2 away 4 away and also 3 away 4 away the Trailers gammon value is about 1.0 or almost perfect.

Cube action tends to be very fast double and very fast pass.

NeilKaz has a rule of 80 to guide cube action at 2 away 4 away. If Trailers plain wins plus gammons are greater than 80%, Leader should drop.

Not sure if that applies to 3 away 4 away or not, but you get the idea of the power of the gammons.

This is a very dangerous position for White to play:

If he gets gammoned he loses.

His own gammons are muted (b/c the overage)

His own recubes are hampered. (Since Black the trailer can take deeper than money)

Quote

07-25-2013 , 09:14 AM

kruidenbuiltje

journeyman

Join Date: Mar 2010 Posts: 270

Hi,

the white position is somewhat awkward with the two wasted checkers on his 1- and 2-point.
In a money game black would not yet have a double, his only asset is his 5-point and his 8-point is stripped.
But on this score 2-1, a redouble from white has wastage, since white only needs 3 points.

I'd say double/take

Quote

07-25-2013 , 09:18 AM

yogiman

adept

Join Date: Jun 2012 Posts: 784

Two conditions of PRaT are met, so according to this rule of thumb it could be a thin double. However, there are very few market losers. Remembering a reference position from Kit Woolsey's book, if the two black checkers would be, say on the 13 point, it would be no double. An extra hit would give black a good racing advantage, but white a possibility to anchor. In cash game it would be borderline. The previous two respondents alerting me to the fact that it is a 3-away, 4 away situation could tip it slightly to the double side, as there is some gammon potential.

Quote

07-25-2013 , 09:27 AM

kruidenbuiltje

journeyman

Join Date: Mar 2010 Posts: 270

Hi,

another remark after reading your spoiler:

The 20% gammons is high, i think it has to do with the following:
Black on his next move will probably escape his 18-blot or anchor on it.
White will split with most of his numbers, black will then attack since the white board is vulnerable.
Hence the 20% gammons.
When white takes the time to cover a/the blot(s) has time to create new builders, thus making a future white split again dangerous.

I now have to agree with the man who believes that 911 was an inside job and say double/pass.

Quote

07-25-2013 , 10:24 AM

yogiman

adept

Join Date: Jun 2012 Posts: 784

Quote:

Originally Posted by kruidenbuiltje

I now have to agree with the man who believes that 911 was an inside job and say double/pass.

Well, you don't have to. According to Gnu Supremo it is too good to double.

Quote

07-25-2013 , 12:27 PM

Taper_Mike

adept

Join Date: Sep 2009 Posts: 1,030

Quote:

Originally Posted by yogiman

Well, you don't have to. According to Gnu Supremo it is too good to double.

During the first couple of days after a position is posed, it's better to let the original poster reveal the bot data or rollout. I think most readers prefer to try to figure out a position on their own. I know I enjoy reading about a person's over-the-board thought process more than I do a recitation of the bot's play.

What you might do in those cases when you want to refer to bot data, such as today, is enclose it in spoiler tags.

Just my two cents.

Mike

Quote

07-25-2013 , 12:31 PM

Taper_Mike

adept

Join Date: Sep 2009 Posts: 1,030

Quote:

Originally Posted by colin20g

Black on roll: What is the correct cube decision for both players?

I have this as a double for sure. Before reading this thread, I think I would have taken. Would White's position be stronger if his two deep blots were joined to make the 1pt?

What were the moves that led up to this position? If they are still available, please post them. Thanks.

Mike

Quote

07-25-2013 , 02:50 PM

colin20g

enthusiast

Join Date: Nov 2012 Posts: 88

It started like this:

Game 3: black starts
White: 2______________ Black: 1
1)_____________________62: 24/18 13/11
2) 32: 6/3 3/1___________33: 25/22 8/5 8/5 11/8
3) 54: 13/8 6/2

Quote

07-26-2013 , 01:41 AM

#10

Taper_Mike

adept

Join Date: Sep 2009 Posts: 1,030

Quote:

Originally Posted by colin20g

It started like this:

Game 3: black starts
White: 2______________ Black: 1
1)_____________________62: 24/18 13/11
2) 32: 6/3 3/1___________33: 25/22 8/5 8/5 11/8
3) 54: 13/8 6/2

Thanks.

I hate it when I roll 32 in reply to a 6-split! I usually play 24/21 13/11, duping 4. Against an opening 62, you can also play both rear checkers up, or even split them, and then slot your 4pt with the deuce! Hitting on the 1pt is a small overplay.

Here’s a 62k XG rollout.

Mike

Code:

XGID=-a----EaC---dEa--c-e----B-:0:0:1:32:0:0:3:0:10

X:Player 1   O:Player 2
Score is X:0 O:0. Unlimited Game, Jacoby Beaver
 +24-23-22-21-20-19------18-17-16-15-14-13-+
 | X              O |   |    O        O  X |
 | X              O |   |    O           X |
 |                O |   |    O           X |
 |                O |   |                X |
 |                O |   |                X |
 |                  |BAR|                  |
 |                X |   |                  |
 |                X |   |                O |
 |                X |   |    X           O |
 |                X |   |    X           O |
 | O              X |   | O  X           O |
 +-1--2--3--4--5--6-------7--8--9-10-11-12-+
Pip count  X: 167  O: 159 X-O: 0-0
Cube: 1
X to play 32

    1. Rollout¹    24/22 24/21                  eq:-0.2543
      Player:   43.93% (G:9.78% B:0.40%)
      Opponent: 56.07% (G:14.42% B:0.56%)
      Confidence: ±0.0021 (-0.2564..-0.2522) - [59.5%]
      Duration: 10 hours 46 minutes

    2. Rollout¹    24/21 6/4                    eq:-0.2547 (-0.0004)
      Player:   44.10% (G:10.63% B:0.43%)
      Opponent: 55.90% (G:15.34% B:0.76%)
      Confidence: ±0.0023 (-0.2570..-0.2524) - [40.4%]
      Duration: 11 hours 31 minutes

    3. Rollout¹    24/21 13/11                  eq:-0.2585 (-0.0041)
      Player:   43.92% (G:10.80% B:0.43%)
      Opponent: 56.08% (G:15.18% B:0.76%)
      Confidence: ±0.0022 (-0.2606..-0.2563) - [0.1%]
      Duration: 10 hours 41 minutes

    4. Rollout²    6/1*                         eq:-0.2770 (-0.0226)
      Player:   43.10% (G:11.69% B:0.38%)
      Opponent: 56.90% (G:15.29% B:0.84%)
      Confidence: ±0.0043 (-0.2812..-0.2727) - [0.0%]
      Duration: 6 hours 26 minutes

    5. Rollout²    13/10 6/4                    eq:-0.2772 (-0.0229)
      Player:   43.74% (G:11.15% B:0.44%)
      Opponent: 56.26% (G:16.14% B:1.07%)
      Confidence: ±0.0033 (-0.2805..-0.2740) - [0.0%]
      Duration: 6 hours 14 minutes

    6. Rollout²    13/8                         eq:-0.2805 (-0.0262)
      Player:   43.21% (G:11.20% B:0.44%)
      Opponent: 56.79% (G:15.56% B:0.79%)
      Confidence: ±0.0031 (-0.2836..-0.2774) - [0.0%]
      Duration: 5 hours 30 minutes

    7. Rollout²    24/22 13/10                  eq:-0.2815 (-0.0272)
      Player:   43.26% (G:10.67% B:0.41%)
      Opponent: 56.74% (G:15.21% B:0.72%)
      Confidence: ±0.0031 (-0.2846..-0.2784) - [0.0%]
      Duration: 5 hours 58 minutes

    8. Rollout³    13/11 8/5                    eq:-0.2864 (-0.0320)
      Player:   43.34% (G:11.70% B:0.45%)
      Opponent: 56.66% (G:16.38% B:1.11%)
      Confidence: ±0.0049 (-0.2912..-0.2815) - [0.0%]
      Duration: 2 hours 00 minute

    9. Rollout4    24/21 8/6                    eq:-0.3046 (-0.0503)
      Player:   42.41% (G:9.99% B:0.37%)
      Opponent: 57.59% (G:14.40% B:0.66%)
      Confidence: ±0.0073 (-0.3119..-0.2973) - [0.0%]
      Duration: 25 minutes 28 seconds


¹  62208 Games rolled with Variance Reduction.
   Dice Seed: 61758585
   Moves and cube decisions: 3-ply

²  31104 Games rolled with Variance Reduction.
   Dice Seed: 61758585
   Moves and cube decisions: 3-ply

³  15552 Games rolled with Variance Reduction.
   Dice Seed: 61758585
   Moves and cube decisions: 3-ply

4  5184 Games rolled with Variance Reduction.
   Dice Seed: 61758585
   Moves and cube decisions: 3-ply


Rollout by David Rockwell
2013-Jun-12
eXtreme Gammon Version: 2.xx
62S-32-dr.xgp
[U=W S4 H23 $23 d26 Z27 %32 C50 w54] "<62**31***15 5 10

Quote

07-29-2013 , 04:44 PM

#11

Dmitriy ObukhovDmi

stranger

Join Date: Jul 2013 Posts: 9

It's a lovely forum you got here.

About position: with two checkers on ace and deuce point it will be very difficult for her to build a threatening home board any time soon. It also means it will be very dangerous for her to split in order to fight for an advanced anchor, because he will be eager to hit (and he got plenty of checkers in the zone already to do that) and try to close her out since hits from the bar are very double edged. I would double this for money in a heartbeat. Even if it is wrong, her game is not so easy to play and she surely will be giving back some of that equity. If it is a gammonish cube for money, it is likely a pass at the score where trailer's gammonish worth almost as much as his single wins. Also, taker's recuse big is reduced at this score.

Double/Pass

Quote

08-06-2013 , 01:47 AM

#12

Wazzle

journeyman

Join Date: Jun 2012 Posts: 349

Quote:

Originally Posted by kruidenbuiltje

Hi,

But on this score 2-1, a redouble from white has wastage, since white only needs 3 points.

I'd say double/take

can you explain this wastage concept, as it applies here? I'm new to the game, and I've mostly just studied cash game play. I've studied little cube theory based on match scores.

Quote

08-06-2013 , 01:49 AM

#13

Wazzle

journeyman

Join Date: Jun 2012 Posts: 349

Quote:

Originally Posted by 911InsideJob

His own gammons are muted (b/c the overage)

His own recubes are hampered. (Since Black the trailer can take deeper than money)

what is overage, if you don't mind? also, what does it mean to take deeper than money?

danke

Quote

08-06-2013 , 04:30 AM

#14

kruidenbuiltje

journeyman

Join Date: Mar 2010 Posts: 270

Hi Wazzle,

it is a match to 5 points

white's score is 2, black's score is 1.

Black has doubled so we play for 2 points now.

If white gets the upper hand later in the game, he can redouble the cube to 4.

If white then wins the game he will score 4 points and win the match at a score of 6-1,
but he would already have won if he had only scored 3 points, since the match is to 5 points.
This 1 point difference 6 versus 5 is a wastage of 1 point.

If black would have won the score would be 2-5, so black would win the match exactly, without wastage.

Overage is the same as wastage.

White will not so soon redouble to 4 (= his recubes are hampered), because black needs exactly 4 points to win the match.
So if the game goes the wrong way, white will not get another chance to try and win the match.

To explain "taking deeper than money" i use another example. Say that you play a long 15-point match and the score is 13-1 for white.
White offers a double, for money the gammonless take point for black is when he has 25% chance.
But in a 15-point match black's chances after passing the cube (the score is then 14-1) are only about 2%.
In that case black's take point is 2%, he can take 23% deeper than for money.
Any chance higher than the 2% after passing is good for black, so he would be happy to take if he had for instance only 5% of winning.

The 5-point match is very special, read the next article and you understand why:

http://www.bkgm.com/articles/GOL/Aug99/fivept.htm

Quote

08-06-2013 , 09:37 AM

#15

colin20g

enthusiast

Join Date: Nov 2012 Posts: 88

It is a double/pass according to rollouts with different settings.

Quote

08-06-2013 , 11:13 PM

#16

Wazzle

journeyman

Join Date: Jun 2012 Posts: 349

@ Kruiden,

thank you for clearing this up. It makes a lot more sense to me now. I think in a cash game this position is a standard early double/ take situation. The fact that in match play the cube for this pos is double/pass and almost too good to double really shows me that match play is very different from cash play.

Quote

08-07-2013 , 12:35 PM

#17

Wazzle

journeyman

Join Date: Jun 2012 Posts: 349

@Kruiden,

I've started to read the article on 5 pt matches, and I'm very impressed. I plan to read it a few times to internalize the info. Having only studied cash play, Im amazed with the way match scores demand different checker play and cube action, even with it comes to something as seemingly meaningless as whether to slot or split with a 21 opener.

Sorry for derailing the thread a little, guys.

Quote

Post Reply Subscribe

...