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the big thread about cube decisions

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06-21-2015 , 10:08 AM

#226

uberkuber

veteran

Join Date: Jul 2009 Posts: 3,091

Double/Drop ?

Quote

06-21-2015 , 10:39 AM

#227

yogiman

adept

Join Date: Jun 2012 Posts: 784

Good try.

Quote

06-22-2015 , 01:38 AM

#228

bleep69

grinder

Join Date: Sep 2008 Posts: 483

I would definitely double as black. As white, I'm a little nervous. My open blot on the 7 point coupled with blacks ammo bearing down to close off his board, would lead me to drop, but I think it is close. I would still drop though.

Quote

06-22-2015 , 02:01 PM

#229

yogiman

adept

Join Date: Jun 2012 Posts: 784

Wow, you guys are becoming better than me. It gets time that I am going to study my own material.

Code:

Cube analysis
Rollout cubeless equity  +0,626

Cubeful equities:
1. Double, pass         +1,000
2. Double, take         +1,054  ( +0,054)
3. No double            +0,761  ( -0,239)
Proper cube action: Double, pass

This position is too complicated to substantiate with numbers. Black can make a 5-board or not, white can enter or not, if white enters he can be sent to the bar again, and the rear checker could also be pointed on.

Remove the blot by covering it, and black has no double:

Code:

Cube analysis
Rollout cubeless equity  +0,334

Cubeful equities:
1. No double            +0,495
2. Double, pass         +1,000  ( +0,505)
3. Double, take         +0,451  ( -0,043)
Proper cube action: No double, take

But this is not only due to the missing blot, but also due to white's point making. Without the point it would have been a double.

I hope someone will confirm or reject the following statement:
If you are on the bar and both have a 4-board, it is generally okay for you to take unless there is a second blot lingering around.
It's a very rough guideline, and I have only seen a couple of instances of this case, so I am quite insecure about it. Likely it is possible to refine the conditions for this directive.

Good thing for black is that he could make a 5-board. Good thing for white is that white's blot on the 17-point is not within easy reach, and that black has made his 1-point. I am not sure whether I am biased by preknowledge, but the 5-board threat weighs heavy, so it would be a pass.

Quote

06-23-2015 , 02:41 AM

#230

bleep69

grinder

Join Date: Sep 2008 Posts: 483

Having a second blot lying around under any situation seems to be cause for concern when the cube is about! I may be able to answer your question more fully in another 10 or so years...

Quote

06-26-2015 , 04:49 AM

#231

yogiman

adept

Join Date: Jun 2012 Posts: 784

Position ID: 5rYBIlC2bUAAOQ Match ID: UqkAAAAAAAAE

White - Pips 134

Black - Pips 147
Black on roll. Cube action?

Quote

06-26-2015 , 05:05 AM

#232

Kamba

enthusiast

Join Date: Feb 2015 Posts: 93

Scary. I think this must be a drop. We need to throw quite a lot of 2's to get out of jail, which swings it in white's favour quite a bit. However, we seem to have a lot of time to do so, especially if we hit those other two checkers. Surely this would be too good if we weren't so stacked on the 24 point. Man, this is actually a tricky one and i'm not quite sure how to work it out.

OTB i would play the player here. Most (that I play against) would drop instantly, so:

Double / Drop

Quote

06-26-2015 , 10:44 AM

#233

Karol Szczerek

enthusiast

Join Date: Mar 2015 Posts: 92

This is prime vs. prime. Those opp's blots in the outfield doesn't matter much. It's all about timing. And with only one outfield spare and 3(!) men behind a broken 6-prime plus one in the gap, it can't be close to a double.

Let's say ou hit one, and he dances - a normal exchange. You still have to hop the 4-pt. prime (20/36) or You are already in big trouble. Even if You hop, You have 2-3-rolls time to get a 2 AND THEN a 5 or 6.

I think this position is rather close to 50/50. There is so much that can go wrong. Yes, we have some gammons, but opp too, for sure.

Maybe it would be a double with only 2 men on 24pt., and a gammon-promoting match score.

Here - never double / lightning take.

Quote

06-26-2015 , 04:59 PM

#234

Fllecha

journeyman

Join Date: Mar 2010 Posts: 321

Its a strage position because, with opponent on the bar with some blots scattered around and what it looks a good timing on our side plus a perfect 5 board, it seems even too good to double. So one can make the correct decision (clear no double, the three man on the 24 point are simply too much a liability) for the wrong reason.

A pretty much interesting question is: how Many players otb would have take? Has everybody considered that black board is static for some time and the blot help white timing?

Again a paradox: for a pratical rule, a double sounds good because you can find a lot of drop otb but here black is not more that 50-50

Quote

06-27-2015 , 12:06 AM

#235

uberkuber

veteran

Join Date: Jul 2009 Posts: 3,091

Quote:

Originally Posted by Kamba

we seem to have a lot of time to do so, especially if we hit those other two checkers.

With all respect, no and no.

Quote

06-28-2015 , 07:54 AM

#236

yogiman

adept

Join Date: Jun 2012 Posts: 784

White - Pips 134

Black - Pips 147
Black on roll. Cube action?
Created with www.BGdiagram.com

Code:

Cube analysis
Rollout cubeless equity  +0,104

Cubeful equities:
1. No double            +0,305
2. Double, pass         +1,000  ( +0,695)
3. Double, take         -0,121  ( -0,426)
Proper cube action: No redouble, take

If black thinks it is too good too double, than he is probably a romancer, nothing wrong here, and there will be quite a few of them in the sphere of games. At the other end of the spectrum there is the predator, who might double, and as a second mistake might hit when he throws 61,62,64,51. As a matter of fact white would have a strong beaver, and should put on a sour face.

It is true that hitting the blots helps white's timing, but the same is true for not hitting plus the slip of a lot of gammons, so black has to hit. In this position it is easier for white to enter, moving black 2 to 7 and white 7 to 8:

Code:

Cube analysis
Rollout cubeless equity  +0,210

Cubeful equities:
1. No double            +0,424
2. Double, pass         +1,000  ( +0,576)
3. Double, take         +0,120  ( -0,303)
Proper cube action: No redouble, take

This is worse for white's timing, but now he has the possibility to anchor on the 2-point.

----

The doubles three to six are bad, because they spoil black's timing to get those rear checkers out. It is also a problem when black doesn't throw a 5 or 6 three times in a row. Those problems will be recurring as long as black has less than two checkers on the 22-point.

So black has still no double with one less on the 1-point, 24 to 3:

Code:

Cube analysis
Rollout cubeless equity  +0,438

Cubeful equities:
1. No double            +0,656
2. Double, pass         +1,000  ( +0,344)
3. Double, take         +0,603  ( -0,053)

Black has still not enough flexibility, though +0,438 is a big improvement.

Unless transferred to the 22-point:

Code:

Cube analysis
Rollout cubeless equity  +0,583

Cubeful equities:
1. Double, take         +0,991
2. Double, pass         +1,000  ( +0,009)
3. No double            +0,835  ( -0,155)
Proper cube action: Redouble, take

It's even almost a pass.

Conclusion:
Black has a double when the following conditions are fulfilled:
– white is on the bar
– black has two checkers on the 22-point
– there are two white blots in the outfield ready to be picked up

Quote

06-28-2015 , 09:57 AM

#237

Fllecha

journeyman

Join Date: Mar 2010 Posts: 321

I clearly said no double because of our 24 men. But i reason about people: Since doubling is -0.12 when he takes and +0.7 if he drop we calculate x(0.7) +(1-x)(-0.12)=0. you find that given 100 opponent we Break even if we find about 12 of them that drop that double. And imo we can easily find them in a random distribution of opponent with no info on their level of play, and the same when you play against the pretty large range 1400-1650 elo players.

Quote

06-28-2015 , 11:15 AM

#238

yogiman

adept

Join Date: Jun 2012 Posts: 784

Nice calculation.

Double, if you think there is a small (=bigger than 12%) chance that he will drop. Ofcourse you can help him with it.

Quote

06-28-2015 , 11:52 AM

#239

Alpha Fish

Pooh-Bah

Join Date: Aug 2008 Posts: 3,917

your calculations would be right if we didn't have our initial +.300 equity, as it is, he needs to drop around 40% for us to breakeven

Quote

06-28-2015 , 02:00 PM

#240

yogiman

adept

Join Date: Jun 2012 Posts: 784

You are right. 38% exactly. You expect to have a reasonable chance that he will drop.

Quote

06-28-2015 , 02:14 PM

#241

Fllecha

journeyman

Join Date: Mar 2010 Posts: 321

My fault: didnt considered our initial equity... Ok case closed.

Quote

06-28-2015 , 11:59 PM

#242

yogiman

adept

Join Date: Jun 2012 Posts: 784

After a good night's sleep.

x(0.7) +(1-x)(-0.12)= 0.30
0.7x + 0.12x = 0.30 + 0.12
x = 0.42/0.82 is about 50%

Quote

06-29-2015 , 03:03 PM

#243

TheRealFatboy

centurion

Join Date: Sep 2013 Posts: 165

the answer has been posted, but i saw it as no double and a MONSTER TAKE, continued reading and was happy to see i got it right. black is in jail, looks like almost a 50/50 game. it's a disaster.

Quote

06-29-2015 , 03:06 PM

#244

TheRealFatboy

centurion

Join Date: Sep 2013 Posts: 165

Quote:

Originally Posted by Karol Szczerek

Karol plays very strong. What he says is worthy of remembering, like Mr Robertie.

Quote

06-30-2015 , 04:04 AM

#245

yogiman

adept

Join Date: Jun 2012 Posts: 784

Quote:

Originally Posted by TheRealFatboy

the answer has been posted, but i saw it as no double and a MONSTER TAKE, continued reading and was happy to see i got it right. black is in jail, looks like almost a 50/50 game. it's a disaster.

I think you deserve a place in a self-proclaimed backgammon lobby of fame.

Quote

06-30-2015 , 02:06 PM

#246

TheRealFatboy

centurion

Join Date: Sep 2013 Posts: 165

Quote:

Originally Posted by yogiman

I think you deserve a place in a self-proclaimed backgammon lobby of fame.

lol.

sadly not even close, im just a beginner trying to get better

but you can have a little dose, wanna play?

Best,

Eric-Fatboy
**** talker HOF world champion(inducted 1993)

Last edited by TheRealFatboy; 06-30-2015 at 02:14 PM.

Quote

06-30-2015 , 02:20 PM

#247

yogiman

adept

Join Date: Jun 2012 Posts: 784

I gain little merit by winning from a beginner, but I lose a lot by being defeated by a beginner. This doesn't look like a take.

Quote

07-01-2015 , 01:59 AM

#248

bleep69

grinder

Join Date: Sep 2008 Posts: 483

Dropping is a huge blunder in this case Yogi, I suggest a take.

Quote

07-01-2015 , 03:12 AM

#249

yogiman

adept

Join Date: Jun 2012 Posts: 784

Look Bleep, it has taken me a lot of pain to build an image here. First a beginner is provoking me into a challenge, and next another beginner is advising me what to do. My selfconfidence starts cracking.