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the big thread about cube decisions

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02-25-2015 , 09:55 AM

#26

Robertie

old hand

Join Date: May 2004 Posts: 1,954

Clear no double. Black needs to make a lot of progress with his back men before he can think about doubling. Move his two back checkers to his 13-point and let White fill in his board a bit so the race differential is about 10 pips and you've got a position which is a bare double and an easy take. The prime doesn't mean much when White has a high anchor.

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02-25-2015 , 11:00 AM

#27

yogiman

adept

Join Date: Jun 2012 Posts: 784

Code:

Cube analysis
Rollout cubeless equity  +0,111

Cubeful equities:
1. No double            +0,172
2. Double, pass         +1,000  ( +0,828)
3. Double, take         -0,101  ( -0,273)
Proper cube action: No double, take (24,8%)

Rollout details:
Centered 1-cube:
  0,555 0,084 0,003 - 0,445 0,083 0,002 CL  +0,111 CF  +0,172
 [0,002 0,003 0,000 - 0,002 0,002 0,000 CL   0,005 CF   0,008]
Player gnubg owns 2-cube:
  0,556 0,083 0,003 - 0,444 0,084 0,002 CL  +0,223 CF  -0,101
 [0,002 0,002 0,000 - 0,002 0,002 0,000 CL   0,011 CF   0,013]
Truncated cubeful rollout (depth 10) with var.redn.
147 games, Mersenne Twister dice gen. with seed 768561025 and quasi-random dice
Stop when std.errs. are small enough: ratio 0,1 (min. 144 games)
Play: world class 2-ply cubeful prune [world class]
keep the first 0 0-ply moves and up to 8 more moves within equity 0,16
Skip pruning for 1-ply moves.
Cube: 2-ply cubeful prune [world class]

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03-01-2015 , 04:23 PM

#28

yogiman

adept

Join Date: Jun 2012 Posts: 784

Position ID: bM4AIG7Eb4cCEA Match ID: MBkAAAAAAAAE

White - Pips 125

Black - Pips 191
White doubles. Take or Pass?
Created with www.BGdiagram.com

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03-01-2015 , 10:38 PM

#29

uberkuber

veteran

Join Date: Jul 2009 Posts: 3,127

I pass this position:

- No connection between back and front positions;
- 3 men on ace point with bar point blocked;
- 2 men on the bar plus one other that might be attacked.

Sure, Black has the better board, but if I look at the big picture, things don't look good.

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03-02-2015 , 02:05 AM

#30

bleep69

grinder

Join Date: Sep 2008 Posts: 483

I pass as well. I addition to the points mentioned by uber, white has plenty of ammunition bearing down on us. White's ungainly stack on the 6 point works against him, but not enough imo.

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03-02-2015 , 10:57 AM

#31

yogiman

adept

Join Date: Jun 2012 Posts: 784

Code:

Cube analysis
Rollout cubeless equity  +0,784

Cubeful equities:
1. Double, pass         +1,000
2. Double, take         +1,361  ( +0,361)
3. No double            +0,967  ( -0,033)
Proper cube action: Double, pass

Even with the knowledge of this rollout, I might take on a sunny day considering the difference in homeboard strength and white's hind checker. One of the better numbers for white is 32, that is, covering and hitting. In this case an average number for black would be to enter two of his three bar checkers without hitting. Tryouts show me that in many cases black still can develop a good (back)game, and sometimes even manages to move forward. And when white is going to hit loose and black manages to hit back, he will likely be back in the game. Also, if black manages to survive in a descent way, the difference in cube dexterity will become important. This rollout might be very flawed, because complicated positions arise with some evaluations which are imo totally off-target.

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03-02-2015 , 12:15 PM

#32

Fllecha

journeyman

Join Date: Mar 2010 Posts: 321

The main problem here is Connectivity because we lost the midpoint and the gap on the 5 point, not the many men back or the men on the bar, cuz opponent has no board.

The pass here is clear but i would suggest to change things:

Fill the 5 point, make a midpoint with the same men on the bar and 4 man back and Now i lean toward a take Now

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03-02-2015 , 02:11 PM

#33

bleep69

grinder

Join Date: Sep 2008 Posts: 483

Isn't the major concern that we have two guys in jail, with a potential third to follow, while white is howling at the gates with ammunition to spare to hit and build points while we try get out? Yes, he has no board, but that's not going to last, and we are going to be likely dancing while he builds it.

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03-02-2015 , 02:51 PM

#34

uberkuber

veteran

Join Date: Jul 2009 Posts: 3,127

32 is a good number, but 11,22,33,44 are just as good and 41,31 are pretty good as well. Add in 43 to the mix and suddenly 1 roll out of 3 is threatening for Black.

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03-02-2015 , 05:05 PM

#35

yogiman

adept

Join Date: Jun 2012 Posts: 784

It is pretty improbable that this would technically be a take with given equity. Still, I would be curious what the outcome would be if you play this position with your friends a number of times.

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03-09-2015 , 12:55 AM

#36

yogiman

adept

Join Date: Jun 2012 Posts: 784

Position ID: 4POGQUBsGzDALA Match ID: MAEAAAAAAAAE

White - Pips 174

Black - Pips 149
White on roll. Cube action?
Created with www.BGdiagram.com

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03-09-2015 , 02:48 AM

#37

bleep69

grinder

Join Date: Sep 2008 Posts: 483

My immediate reaction is no double/take, but my reasons are a little vague. White has the better trap, but little ammunition to add to it in the short term. In the meantime he has a fair amount of work to do getting his back men out. The exposed blot, and the trapped blot don't strike me as massive weaknesses, as they will escape in short order, and possible form an anchor in the process.

The main problem with most decisions in backgammon at my level is I can make a convincing case (to myself) for either course of action, depending on what my initial thoughts are. Fundamental principles seem hard to come by, and hard to learn, as the presence of a single blot somewhere means you are dealing with a different principle to the one you thought was relevant.

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03-09-2015 , 06:56 AM

#38

yogiman

adept

Join Date: Jun 2012 Posts: 784

You are right. According to the rollout it is a perfect draw.

Code:

Cube analysis
Rollout cubeless equity  +0,478

Cubeful equities:
1. No double            +0,709
2. Double, pass         +1,000  ( +0,291)
3. Double, take         +0,709  ( -0,000)
Proper cube action: No double, take (0,0%)

White has too little ammunition to corner black. Get a back checker further up to his 13-point, and it will be a pass.

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03-09-2015 , 07:32 AM

#39

uberkuber

veteran

Join Date: Jul 2009 Posts: 3,127

Damn, was thinking double/pass.

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03-10-2015 , 09:11 AM

#40

yogiman

adept

Join Date: Jun 2012 Posts: 784

Position ID: 2M6YAUiTnSPgAA Match ID: cAkAAAAAAAAE

White - Pips 148

Black - Pips 122
Black on roll. Cube action?
Created with www.BGdiagram.com

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03-10-2015 , 03:24 PM

#41

peachpie

centurion

Join Date: Aug 2014 Posts: 182

I say double/pass. I don't think it is too good quite yet.

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03-10-2015 , 06:08 PM

#42

uberkuber

veteran

Join Date: Jul 2009 Posts: 3,127

I'm not sure if it's take or pass, so probably a double.
From PRAT criteria, I lean towards a pass.

Quote

03-11-2015 , 03:06 AM

#43

yogiman

adept

Join Date: Jun 2012 Posts: 784

Code:

Cube analysis 
Rollout cubeless equity  +0,554 

Cubeful equities: 
1. Double, take         +0,874 
2. Double, pass         +1,000  ( +0,126) 
3. No double            +0,744  ( -0,131) 
Proper cube action: Double, take

Black is well ahead in the race. There is a reasonable thread to hit the second checker. But black's hind checkers have a continuity problem, and white's inner board is superior. That's enough compensation to make it a fat take. Even if the black checker on the 11 point is moved (in direct cover range) to the 9 point, it is a good take:

Code:

Cube analysis
Rollout cubeless equity  +0,584

Cubeful equities:
1. Double, take         +0,922
2. Double, pass         +1,000  ( +0,078)
3. No double            +0,760  ( -0,161)
Proper cube action: Double, take

It would be a very convincing pass, if black's board would not be interrupted:

Black on roll. Cube action?

Code:

Cube analysis
Rollout cubeless equity  +0,719

Cubeful equities:
1. Double, pass         +1,000
2. Double, take         +1,269  ( +0,269)
3. No double            +0,942  ( -0,058)
Proper cube action: Double, pass

Quote

03-11-2015 , 11:25 AM

#44

yogiman

adept

Join Date: Jun 2012 Posts: 784

Position ID: bt5gCARwb48BAA Match ID: cAkAAAAAAAAE

White - Pips 102

Black - Pips 107
Black on roll. Cube action?
Created with www.BGdiagram.com

Quote

03-11-2015 , 07:56 PM

#45

uberkuber

veteran

Join Date: Jul 2009 Posts: 3,127

Easy take I would guess. Not quite a double I think.
No double/take.

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03-12-2015 , 12:43 AM

#46

Taper_Mike

adept

Join Date: Sep 2009 Posts: 1,030

All the doublets play well, as do a few other POH numbers and several hitting aces. I’d cube based on volatility. Down by only 5 pips, and holding the better board, I would take.

Mike

Quote

03-12-2015 , 01:20 AM

#47

bleep69

grinder

Join Date: Sep 2008 Posts: 483

Double/take, but close to no double. There is a decent chance that we can get white caught up as we develop our base. Easy take because there's also a decent chance that white slips through. black won't want to hit loose, so only the rolls that hit and cover are any good to him.

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03-12-2015 , 02:01 AM

#48

bleep69

grinder

Join Date: Sep 2008 Posts: 483

Quote

03-12-2015 , 04:38 AM

#49

Kamba

enthusiast

Join Date: Feb 2015 Posts: 93

I would be very reluctant to double here. Purely because the pip count is so close. But perhaps that is too timid.

Quote

03-12-2015 , 08:40 AM

#50

yogiman

adept

Join Date: Jun 2012 Posts: 784

Code:

Cube analysis
Rollout cubeless equity  +0,494

Cubeful equities:
1. Double, take         +0,798
2. Double, pass         +1,000  ( +0,202)
3. No double            +0,685  ( -0,113)
Proper cube action: Double, take

Black has quite a few marketlosers. 11,22,33,44,42,41,21 hit and lengthen the prime, 55 and 66 give a victorious shot ahead, and 16 has some gammon potential. What rule of thumb we could take recourse to in order to decide whether this is a take? I would say, look to the gammon potential and look if white has some chances to work his way out.

Here there is not so much gammon potential overall. Viewing white's chances, more than half of blacks numbers are not very succesful, the race is close, and black might have to hit loose with white at the edge of the 5-prime.

But I wouldn't be surprised if I would have accepted the cube out of bravado.

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