Position of the Day 02-18-25 - Instructive Cube

[ View Thread ] [ Post Response ] [ Return to Index ] [ Read Prev Msg ] [ Read Next Msg ]

BGonline.org Forums

Position of the Day 02-18-25 - Instructive Cube - Rollout and more development

Posted By: pierrez
Date: Friday, 21 February 2025, at 1:06 p.m.

In Response To: Position of the Day 02-18-25 - Instructive Cube for Intermediate Players - Rollout (Stick)

Consider diagram A and diagram B :
      
Diagram A

White is Joueur 2

score: 0
pip: 92

Unlimited Game
Jacoby Beaver

pip: 80
score: 0

Blue is Joueur 1

XGID=-BBb-BCBD----------cbbbbb-:0:0:1:00:0:0:3:0:10
Blue on roll, cube action?

Analyzed in Rollout No double Double/Take
Player Winning Chances: 73,48% (G:1,72% B:0,01%) 73,56% (G:1,59% B:0,01%)
Opponent Winning Chances: 26,52% (G:1,04% B:0,01%) 26,44% (G:1,03% B:0,01%)
Cubeless Equities +0,477 +0,954
Cubeful Equities
No double: +0,805 (-0,007) ±0,007 (+0,797..+0,812)
Double/Take: +0,811 ±0,009 (+0,802..+0,821)
Double/Pass: +1,000 (+0,189)

Best Cube action: Double / Take
Rollout details
1296 Games rolled with Variance Reduction.
Moves: 3-ply, cube decisions: XG Roller

Double Decision confidence: 87,2%
Take Decision confidence: 100,0%
Duration: 9 minutes 04 seconds

eXtreme Gammon Version: 2.19.211.pre-release
Diagram B

White is Joueur 2

score: 0
pip: 66

Unlimited Game
Jacoby Beaver

pip: 80
score: 0

Blue is Joueur 1

XGID=-BBb-BCBD-------------bef-:0:0:1:00:0:0:3:0:10
Blue on roll, cube action?

Analyzed in Rollout No double Double/Take
Player Winning Chances: 76,29% (G:5,78% B:0,07%) 76,19% (G:5,88% B:0,11%)
Opponent Winning Chances: 23,71% (G:0,35% B:0,00%) 23,81% (G:0,38% B:0,00%)
Cubeless Equities +0,581 +1,160
Cubeful Equities
No double: +0,877 (-0,120) ±0,006 (+0,871..+0,884)
Double/Take: +0,998 ±0,010 (+0,987..+1,008)
Double/Pass: +1,000 (+0,002)

Best Cube action: Double / Take
Rollout details
1296 Games rolled with Variance Reduction.
Moves: 3-ply, cube decisions: XG Roller

Double Decision confidence: 100,0%
Take Decision confidence: 67,8%
Duration: 5 minutes 38 seconds

eXtreme Gammon Version: 2.10

What is very interesting in the Stick’s position, is the fact that if one changes continuously the White homeboard from the original one to a closed board (Diagram A) then to a crushed board (Diagram B), we are staying permanently in the Double/Take window.
The original position and diagram B are the endpoints of the doubling window.
Whites chances are lying in (moving from) hitting with unpassable strong homeboard (original position to Diagram A) to an almost straight race (Diagram B).
Technically speaking, I would classify this position as “an anchor with a gap in front of” instead of “a phantom backgame” for two reasons :
1 - If the gap was behind the anchor, it still looks like a phantom backgame but it will obviously never be a take
2 - In a backgame position, the attacking side may expect for a double digit percentage of gammons when the defender may expect for a double shot. That will never happen here
Super cool position.