In the next few posts I will try to explain what went wrong and how to choose the best play, and I hope it will be useful to you.
But, first things first - let's see the answers for the positions from the last post.
The positions from the last time should have been easy, if you didn't miscount chances for bearing off.
1.
 is Player 2score: 0 pip: 7 | ||||||||||||||||
 | ||||||||||||||||
| Unlimited Game | ||||||||||||||||
| pip: 3 score: 0  is Player 1 | ||||||||||||||||
| XGID=-AA------------------aa---:1:-1:-1:00:0:0:0:0:10 | ||||||||||||||||
| on roll, cube action? | ||||||||||||||||
| Analyzed in XG Roller+ | No redouble | Redouble/Take |
| Player Winning Chances: | 47,22% (G:0,00% B:0,00%) | 47,22% (G:0,00% B:0,00%) |
| Opponent Winning Chances: | 52,78% (G:0,00% B:0,00%) | 52,78% (G:0,00% B:0,00%) |
| Cubeless Equities | -0,056 | -0,111 |
| Cubeful Equities | ||
| No redouble: | -0,056 | |
| Redouble/Take: | -0,111 (-0,056) | |
| Redouble/Pass: | +1,000 (+1,056) | |
| Best Cube action: No redouble / Take | ||
| Percentage of wrong pass needed to make the double decision right: 4,8% | ||
Again we can use shortcuts mentioned in last two posts.
We start by noticing if the top player trows a 1 or a 2 he will not bear off. The chance to throw either 1 or 2 is 20 of 36 rolls. So 16 rolls bear off, 20 rolls don't.
Now to see how the doubles play. 11 doesn't bear off, but 22 does. That's a total of 17 rolls.
17 rolls bear off, 19 don't.
That's less than a half so top player shouldn't double. If he doubles, you should beaver (turn the cube to the next value while keeping the cube).
2.
| is Player 2 score: 0 pip: 6 | ||||||||||||||||
| | ||||||||||||||||
| Unlimited Game | ||||||||||||||||
| pip: 3 score: 0 is Player 1 | ||||||||||||||||
| XGID=-AA-----------------a---a-:1:-1:-1:00:0:0:0:0:10 | ||||||||||||||||
| on roll, cube action? | ||||||||||||||||
| Analyzed in XG Roller+ | No redouble | Redouble/Take |
| Player Winning Chances: | 63,89% (G:0,00% B:0,00%) | 63,89% (G:0,00% B:0,00%) |
| Opponent Winning Chances: | 36,11% (G:0,00% B:0,00%) | 36,11% (G:0,00% B:0,00%) |
| Cubeless Equities | +0,278 | +0,556 |
| Cubeful Equities | ||
| No redouble: | +0,278 (-0,278) | |
| Redouble/Take: | +0,556 | |
| Redouble/Pass: | +1,000 (+0,444) | |
| Best Cube action: Redouble / Take | ||
Using our shortcuts, we see that your opponent needs either a 5 or a 6 to bear off. That's 20 rolls.
How do doubles play? 66 and 55 are already included in "either a 5 or a 6", 44 bears off, 33 bears off, 22 bears off. 11 doesn't bear off. Three more rolls.
23 rolls bear off, 13 don't. 13 is more than 9 (25% of 36) so you have an easy take.
3.
| is Player 2 score: 0 pip: 4 | ||||||||||||||||
| | ||||||||||||||||
| Unlimited Game | ||||||||||||||||
| pip: 3 score: 0 is Player 1 | ||||||||||||||||
| XGID=-AA--------------------b--:1:-1:-1:00:0:0:0:0:10 | ||||||||||||||||
| on roll, cube action? | ||||||||||||||||
| Analyzed in XG Roller+ | No redouble | Redouble/Take |
| Player Winning Chances: | 72,22% (G:0,00% B:0,00%) | 72,22% (G:0,00% B:0,00%) |
| Opponent Winning Chances: | 27,78% (G:0,00% B:0,00%) | 27,78% (G:0,00% B:0,00%) |
| Cubeless Equities | +0,444 | +0,889 |
| Cubeful Equities | ||
| No redouble: | +0,444 (-0,444) | |
| Redouble/Take: | +0,889 | |
| Redouble/Pass: | +1,000 (+0,111) | |
| Best Cube action: Redouble / Take | ||
In order to fail to bear off, he must roll a one; as we know from our shortcuts, that's 11 rolls that don't bear off.
But, double 1's do bear off, so 10 rolls don't bear off.
That's slightly more than needed 9 rolls and you should take.
4.
| is Player 2 score: 0 pip: 8 | ||||||||||||||||
| | ||||||||||||||||
| Unlimited Game | ||||||||||||||||
| pip: 3 score: 0 is Player 1 | ||||||||||||||||
| XGID=-AA-----------------a-a---:1:-1:-1:00:0:0:0:0:10 | ||||||||||||||||
| on roll, cube action? | ||||||||||||||||
| Analyzed in XG Roller+ | No redouble | Redouble/Take |
| Player Winning Chances: | 38,89% (G:0,00% B:0,00%) | 38,89% (G:0,00% B:0,00%) |
| Opponent Winning Chances: | 61,11% (G:0,00% B:0,00%) | 61,11% (G:0,00% B:0,00%) |
| Cubeless Equities | -0,222 | -0,444 |
| Cubeful Equities | ||
| No redouble: | -0,222 | |
| Redouble/Take: | -0,444 (-0,222) | |
| Redouble/Pass: | +1,000 (+1,222) | |
| Best Cube action: No redouble / Take | ||
| Percentage of wrong pass needed to make the double decision right: 13,3% | ||
We can again start by "either a 5 or a 6", and that's 20 rolls that bear off.
Now we subtract rolls containing a 5 or a 6 that don't bear off. 51, 52, 61, 62 don't bear off. That's 8 rolls. Now 20-8 = 12 rolls which bear off.
How do doubles play? 44 bears off, 33 bears off. 22 doesn't bear off. Now we have 14 rolls total which bear off.
14 is less than 18 (50% of 36) so he should not double as he is not a favorite to win this game. If he makes a mistake and doubles, you can beaver if you're playing unlimited session (in a match play you cannot beaver).
This position is from my match against a relatively strong player and he made a blunder here, so even a stronger player can make errors in positions like this one:
| is Player 1 score: 0 pip: 104 | ||||||||||||||||
 | Unlimited Game | |||||||||||||||
| | pip: 142 score: 0 is Player 2 | |||||||||||||||
| XGID=-----BEbB-B--B---bbdBb-c--:1:1:1:44:0:0:0:0:10 | ||||||||||||||||
| to play 44 | ||||||||||||||||
What is your move here, and please explain the reasons behind your move:
a) 20/12(2)
b) 20/16(2) 13/9(2)
c) 20/16 20/8
d) 20/16(2) 6/2(2)
e) 13/9(2) 6/2(2)
f) 10/2(2)
g) 8/4(2) 6/2(2)
h) 6/2(2) 5/1(2)
i) something else - what?
c) 20/16(2) 6/2 (2)
ReplyDeleteI think making a 2pt is a must in case I hit him, especially with so many spare checkers stacked on my 6pt. I'm not sure about the second part of the move - 13/9 gives my opponent a chance to escape with if he rolls 66. I think it is very important to maintain the midpoint as long as he is down there - I want to be able to get him when he has to split.
If I play the selected move my opponent has only 2 rolls to escape safely from me.
Actually by blocking him in my outer board and "unblocking" him in his board (and hoping he doesn't roll 44 or 55) I am actually pushing him to enter his homeboard with his outer board points while trying not to split his 18pt. At one point he will have to split them and this is when I attack. The only problem is that I also need to move my checkers in the upcoming rolls. So now I'm not sure what to do :)
I hope this is a good enough reason to move from his 5pt. But if he rolls 55 or 44 the match is pretty much over. Backgammon is a game of luck and statistics anyway, so I choose this move :)
g) 8/4(2) 6/2(2) because we are behind in the race, so it's better to stay behind with the back checkers (that are moreover comfortably anchored on the golden point) and build a strong home board, while waiting for the decisive shot.
ReplyDeleteUnstacking the 6 point is a plus.
g) 8/4(2) 6/2(2) for me too:
ReplyDeleteI wanna have the stronger homefield than my opponent
and if behind stay behind