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Last post, I made many huge mistakes fighting the backgame. This time I make several horrible plays as the backgamer. The next several positions are scenes from the first game of an 11 point match.
1) 11 to play.
is Grant score: 0 pip: 99 | ||||||||||||||||
11 point match | ||||||||||||||||
pip: 174 score: 0 is Bill | ||||||||||||||||
XGID=--B--BB-B--a-B--cb-dCcbB--:0:0:1:11:0:0:0:11:10 | ||||||||||||||||
to play 11 |
1. | XG Roller++ | 13/11* 8/7(2) | eq: -0.416 | |||
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2. | XG Roller++ | 13/12 13/11* 11/10 | eq: -0.500 (-0.084) | |||
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3. | 3-ply | 13/11*(2) | eq: -0.494 (-0.078) | |||
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eXtreme Gammon Version: 2.10, MET: Kazaross XG2
I moved 13/11*/10, 13/12. I hit an early shot and now have the rare chance of winning the backgame by going forward. My strategy was to spread my checkers around to patrol the outfield with this play.
I think the concept is OK actually, but double 1's gives me an opportunity to improve my structure which I shouldn't pass up. Namely, by moving 13/11*, 8/7(2) I open the possibility of forming a full prime. The 8 point and 2 point are seven points apart and can never be part of the same prime. Related to this concept, it is possible for Grant to enter poorly on the ace point and get stuck there - but only if I advance to the bar point.
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2) Grant has escaped and now I am back to normal backgame mode. 31 to play.
is Grant score: 0 pip: 91 | ||||||||||||||||
11 point match | ||||||||||||||||
pip: 175 score: 0 is Bill | ||||||||||||||||
XGID=--B--BB-BA----A-db-cBccBA-:0:0:1:31:0:0:0:11:10 | ||||||||||||||||
to play 31 |
1. | XG Roller++ | 8/4 | eq: -0.830 | |||
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2. | XG Roller++ | 24/20 | eq: -0.910 (-0.080) | |||
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3. | XG Roller+ | 23/20 2/1 | eq: -1.314 (-0.483) | |||
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eXtreme Gammon Version: 2.10, MET: Kazaross XG2
Clearly leaving my man on the ace point is the "DMP" play, since I need a hit and maximizing contact gives the most chances to hit something. On the other hand, this contact is double-edged since I could be pointed on or simply hit loose and miss, at which point I am sure to get gammoned more. How to judge this tradeoff?
I was pleased to get out of harm's way with 24/20 and lessen the gammon threat but this turns out to be the wrong idea.
The computer likes 8/4. The evaluation shows I get more than enough extra wins to compensate for the extra gammon losses.
However, I think the main reason has to do with cube position. By staying back, the computer thinks Grant is just shy of a cube. By jumping up, the computer thinks Grant has a dig double. So perhaps I get gammoned less since sometimes Grant hits loose and I miss or points on me and I dance. In these instances Grant blows by his market and wins only one point. Compare to my play where by jumping up I give Grant an efficient double that I must take - frequently losing 2 or 4 points.
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3) Once again I hit an early shot and get to try to win going forward. 55 to play.
is Grant score: 0 pip: 89 | ||||||||||||||||
11 point match | ||||||||||||||||
pip: 181 score: 0 is Bill | ||||||||||||||||
XGID=--B--BB-Ba----A-cA-cCddA-A:0:0:1:55:0:0:0:11:10 | ||||||||||||||||
to play 55 |
1. | XG Roller++ | Bar/15 20/15 14/9* | eq: -0.459 | |||
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2. | XG Roller++ | Bar/20 14/9* 8/3(2) | eq: -0.664 (-0.205) | |||
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3. | XG Roller+ | Bar/15 17/12 14/9* | eq: -0.455 (+0.004) | |||
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eXtreme Gammon Version: 2.10, MET: Kazaross XG2
I made the board with Bar/20, 14/9*, 8/3(2). The problem with this play is am too disconnected and lack outfield control. While making the board is desirable it is premature. I still have six men stuck on Grant's side of the board and am too far away from threatening to close the fifth point in my board.
Therefore, my priority is to extricate my back men and control the outfield. I am going to need to hit Grant's several more times as he tries to escape, so I should prepare my men for this task. The computer likes, Bar/20, 14/9*, 20/15(2) but equally respectable is Bar/20, 14/9*, 20/15, 17/12. These plays all move plenty of ammo into the outfield from where they patrol the escape zone.
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4) 64 to play.
is Grant score: 0 pip: 98 | ||||||||||||||||
11 point match | ||||||||||||||||
pip: 161 score: 0 is Bill | ||||||||||||||||
XGID=a-BB-BB--A------cA-cDddA--:0:0:1:64:0:0:0:11:10 | ||||||||||||||||
to play 64 |
1. | XG Roller++ | 20/14 17/13 | eq: -0.239 | |||
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2. | XG Roller++ | 23/13 | eq: -0.292 (-0.053) | |||
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3. | 3-ply | 20/10 | eq: -0.299 (-0.060) | |||
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eXtreme Gammon Version: 2.10, MET: Kazaross XG2
Once again the theme is to flood the outfield in order to control the escape zone territory. If Grant pops in and out with a four I need to be ready to hit him in the outer board. Therefore, 20/14, 17/13 is the play.
I got panicky about my back blot being vulnerable and popped him out with 23/13. Besides being wimpy and the wrong strategy, I should have been wanting to unstack my checkers on the 5 point anchor.
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5) 63 to play.
is Grant score: 0 pip: 111 | ||||||||||||||||
11 point match | ||||||||||||||||
pip: 95 score: 0 is Bill | ||||||||||||||||
XGID=aBCaBBC----A----b--cBdd---:1:-1:1:63:0:0:0:11:10 | ||||||||||||||||
to play 63 |
1. | XG Roller++ | 20/14 6/3* | eq: +1.074 | |||
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2. | XG Roller++ | 11/5 6/3* | eq: +0.974 (-0.101) | |||
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3. | 3-ply | 20/17 11/5 | eq: +0.971 (-0.104) | |||
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eXtreme Gammon Version: 2.10, MET: Kazaross XG2
I attribute this mistake to playing on autopilot. I moved 11/5, 6/3*. Hit loose, bring in a direct cover, pick up the dice. Easy. Right? Wrong.
After my play notice 42 and 22 don't cover so I only have 8 covers. Also, 44 is a horror show.
After the correct 20/14*, 6/3* it turns out I also have 8 covers! All 8's work plus 65 so the covers are the same, but 44 plays fine and is clearly more flexible.
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6) I lead 9 away 11 away. 32 to play from the air.
is Grant score: 0 pip: 138 | ||||||||||||||||
11 point match | ||||||||||||||||
pip: 144 score: 2 is Bill | ||||||||||||||||
XGID=-aBaB-B-C--BaB--acbd-b-A-A:0:0:1:32:2:0:0:11:10 | ||||||||||||||||
to play 32 |
1. | XG Roller++ | Bar/20 | eq: -0.400 | |||
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2. | XG Roller++ | Bar/23 11/8 | eq: -0.626 (-0.226) | |||
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3. | 3-ply | Bar/22 8/6 | eq: -0.407 (-0.007) | |||
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eXtreme Gammon Version: 2.10, MET: Kazaross XG2
This one is embarassing. I looked for the security of the anchor with Bar/23, 11/8.
I needed to realize that "playing safe" is actually the riskiest play of all. I am drifting into a bad position which will not age well.
Instead I need to recognize I have a bad position and need to make a bid for an anchor now before it's too late. Bar/20 is called for. For this roll only I have the better board and Grant has some loose blots that need tidying up before he can double. I absolutely need to take a chance now by coming up to his five point and hope for the best.
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7) Score is 9 away 7 away and I hold a four cube. 53 from the bar. In and out or in and kill?
is Grant score: 4 pip: 94 | ||||||||||||||||
11 point match | ||||||||||||||||
pip: 74 score: 2 is Bill | ||||||||||||||||
XGID=-DBaBCC---aa-------cbb-bcA:2:1:1:53:2:4:0:11:10 | ||||||||||||||||
to play 53 |
1. | XG Roller++ | Bar/17 | eq: +0.300 | |||
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2. | XG Roller++ | Bar/22 6/1 | eq: +0.080 (-0.220) | |||
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eXtreme Gammon Version: 2.10, MET: Kazaross XG2
Once again I made the superficially "safe" play Bar/22, 6/1 which is actually not safe at all.
If I had properly came out with Bar/17 it is true I step into a lot of shots but this my best chance to win. Grant would have all sixes and sevens to hit (17 sixes plus 52 and 43 or 21 hitters) but if Grant misses I can send a powerful 8 cube which he will probably have to drop. So by stepping out I basically get a significant free shot at winning the game right now.
On the other hand by staying back, Grant has all threes, 11's and 12's to hit. I am not sure if he chooses to hit with all these rolls but he does with most of them. It is true I hit back ~30% of the time when he hits loose but bottom line is I am giving him extra sequences to win. Why? Well, he either hits loose when I am a big underdog to win, -or- he simply makes a move in the outfield. Then, and this is the kicker, I am hoping to roll number to get into the outfield where he will have a double shot at me!! So if a good scenario is I move into a doubleshot next turn... why not just do it now?
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8) Later in the same game. I trail 9 away 7 away and am holding a 4 cube. Cube action?
is Grant score: 4 pip: 14 | ||||||||||||||||
11 point match | ||||||||||||||||
pip: 26 score: 2 is Bill | ||||||||||||||||
XGID=-DAACA-----------------ed-:2:1:1:00:2:4:0:11:10 | ||||||||||||||||
on roll, cube action? |
Analyzed in XG Roller++ | No redouble | Redouble/Take |
Player Winning Chances: | 46.59% (G:0.00% B:0.00%) | 46.58% (G:0.00% B:0.00%) |
Opponent Winning Chances: | 53.41% (G:0.00% B:0.00%) | 53.42% (G:0.00% B:0.00%) |
Cubeless Equities | -0.068 | +0.126 |
Cubeful Equities | ||
No redouble: | +0.167 | |
Redouble/Take: | +0.127 (-0.040) | |
Redouble/Pass: | +1.000 (+0.833) | |
Best Cube action: No redouble / Take | ||
Percentage of wrong pass needed to make the double decision right: 4.4% |
eXtreme Gammon Version: 2.10, MET: Kazaross XG2
I know this is a snore of a take but is it a double? Winning 8 points would be sweet but is it worth putting the matchon the line?
I am not math oriented when it comes to backgammon. I guessed I was about 50/50 to win from here and also guessed my doubling window would open at about 50%. This was based on nothing at all except a hunch. Turns out this is a no double but I wasn't too far off.
Alter the score my making me trail by 3 points instead of three and then the position is a correct Double / Take.
Good positions, Bill. In position 6, how bad is bar/22 8/6? That was what I wanted to play. I see you have it analyzed on 3-ply but not XGR++.
ReplyDeleteBeats me. Didn't notice that.
ReplyDelete