Game 4, move 2 : Herd 6-1

[diane]

move?

[KDP]

Spoiler

making the bar is tempting, especially with only his one point board, but why leave a shot when you dont have to.  15-8

[close]

[ah_clem]

Spoiler

I count 16 shakes that hit us if we make the bar point.  That's almost 50%.  Meanwhile we have an opportunity to lock in a 15 pip lead for a couple of rolls at least.  Big numbers can be played off the midpoint, small numbers can be dumped behind the anchor.  So while I hate the stacks,  I think safteying the blot is the way to go.

Also, with Linus having made the GP and with no other checkers back the bar point is not worth as much as usual.

15/8

[close]

[ah_clem]

XGR++

Spoiler

Making the bar point here is a massive blunder.  I was thinking it would be something like a .08 error, but it's a triple whopper with cheese.



XGID=-----bE-C---dF-Aac-e------:0:0:1:61:3:1:0:5:10

X:Player 1   O:Player 2
Score is X:3 O:1 5 pt.(s) match.
+13-14-15-16-17-18------19-20-21-22-23-24-+
| X     X  O  O    |   | O                |
| X           O    |   | O                |
| X           O    |   | O                |
| X                |   | O                |
| 6                |   | O                |
|                  |BAR|                  |
|                  |   | X                |
| O                |   | X                |
| O           X    |   | X                |
| O           X    |   | X  O             |
| O           X    |   | X  O             |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count  X: 147  O: 155 X-O: 3-1/5
Cube: 1
X to play 61

    1. XG Roller++ 15/8                         eq:+0.352
      Player:   62.79% (G:1.55% B:0.03%)
      Opponent: 37.21% (G:1.19% B:0.02%)

    2. XG Roller++ 13/7 8/7                     eq:+0.003 (-0.349)
      Player:   55.93% (G:4.23% B:0.13%)
      Opponent: 44.07% (G:6.63% B:0.14%)

    3. 1-ply       15/14 13/7                   eq:-0.019 (-0.370)
      Player:   54.24% (G:4.39% B:0.14%)
      Opponent: 45.76% (G:6.90% B:0.20%)

    4. 1-ply       13/6                         eq:-0.091 (-0.443)
      Player:   52.50% (G:4.37% B:0.13%)
      Opponent: 47.50% (G:7.74% B:0.17%)

    5. 1-ply       15/9 8/7                     eq:-0.096 (-0.447)
      Player:   52.61% (G:5.09% B:0.15%)
      Opponent: 47.39% (G:8.24% B:0.21%)


eXtreme Gammon Version: 2.10, MET: Kazaross XG2

[close]

[diane]

This is surprising...it is the kind of play where I would almost always play the safe option, but deep down be wishing I was brave enough to make the other play, which seems to do more. Especially in this case, where it seems almost harmless..after all, he has no board yet, the game is young enough to encourage a more cavalier approach. Add that to what moving 15/8 doesnt do, I really don't understand that massive difference...

[ah_clem]

The thing is, making the bar point accomplishes very little here.  When your opponent is sitting on the ace point, making your bar point is a huge asset - it blocks 6's (and with 5's already blocked it effectively blocks all big rolls)  plus it starts a prime that can be extended in both directions.

By contrast, with your opponent having made your 5 point, the bar point doesn't block squat and will never grow into a full prime.  Yeah, you might make the 9 point but it will be highly unlikely that you will ever make the 10 and 11 points.

Since making the bar does so little, there's no reason to take risks to achieve so little gain.  As for what 15/8 does, it safties our runner, meaning we have now escaped both backmen, have no blots, and a nice 15 pip lead.   That's not so bad, and is a significant improvement to the starting position.

[Zorba]

All good points. Some other things to consider: we already escaped one backchecker to safety, and now we have a chance to get the second one safe, and we have a nice racing lead. With Linus holding a high anchor, we have pretty good chances to just bring this one home, dumping behind the anchor while waiting for doubles to clear the mid. So, not much need to take risks here, when 15/8 already makes us a good favorite.

If the checker on 15 was the first backchecker we were trying to escape, making the bar would be more attractive as we're far from turning it into some kind of midpoint vs. high anchor game (yet), and a generally strong asset would be valuable in many gameplans. Indeed, I've seen many times the bot recommend making the bar with a 6-1 rather than safetying the first escaped backchecker.

Adding to the size of the blunder of 13/7 8/7 here must be the matchscore. 15/8 creates a very low gammon rate, which is very good for us in case Linus wants to double at some point (his gammon wins on a 2-cube win the match and have huge value). Making the bar risks getting the lonely backchecker attacked and could lead to some gammon losses.