Position # 46

[PersianLord]

Position information:

Pip-count: Red  131-153 White
Score:       Red     2-0   White
Match:                   3-pointer

Spoiler

Red has a very strong position here. He needs just 1 pt to win the whole match and he has a 5-pt prime. Hitting is a bad mistake here, because it gives white a possibility to play a backgame. After hitting, any 1, plus 43, would give white a double-anchor backgame and that would knock the sh** out of red. I think hadn't white had that blot on red's ace pt, hitting would have come right. Anyway, red should play safe here and make an anchor with the 6. With 2, the 13/11 is the best.

    1. Cubeful 2-ply    24/18 13/11                  Eq.:  +0.511
        75.8%  25.3%   1.3% -  24.2%   4.7%   0.1%        2-ply cubeful prune [world class]
    2. Cubeful 2-ply    24/18 9/7                    Eq.:  +0.465 ( -0.046)
        73.6%  26.6%   1.4% -  26.4%   6.1%   0.1%
        2-ply cubeful prune [world class]
    3. Cubeful 2-ply    24/22*/16                    Eq.:  +0.447 ( -0.064)
        72.6%  34.4%   2.8% -  27.4%   4.3%   0.1%
        2-ply cubeful prune [world class]
    4. Cubeful 2-ply    24/22* 13/7                  Eq.:  +0.409 ( -0.102)
        70.7%  37.4%   4.0% -  29.3%   4.7%   0.1%
        2-ply cubeful prune [world class]
    5. Cubeful 2-ply    18/10                        Eq.:  +0.389 ( -0.122)
        69.9%  29.6%   2.4% -  30.1%   6.7%   0.2%
        2-ply cubeful prune [world class]

[close]

[socksey]

Spoiler

I voted 24/18 13/11 Not to hit so you don't leave the chance for white to block your 1 pt for a great backgame for him.  Blocking red's 7 pt is also a good thing.

[close]

Would be nice for other voters to explain their choice in spoiler form, of course. 

Happy to see the problems appear again, PersianLord!  Thanks!  

socksey



"Diamonds are nothing more than chunks of coal that stuck to their jobs." - Malcolm Stevenson Forbes

[Zorba]

Good instructive position, PL!

Spoiler

This is a good position to analyze even without the specific roll.

The matchscore means this is basically a DMP game, where only single wins are important. The exception is White winning a backgammon for the match, but that's rare from the starting position and even rarer from here! Safe to ignore this, and just look at single wins.

DMP games make certain game plans more attractive; on the defense, there is no fear of a (back)gammon loss anymore, so deep anchor games and backgames are more attractive. You can stay back as long as you wish, for that last ditch shot.

The board. Red has pinned down 3 of White's checkers behind a very strong blockade, which might turn into a full 6-prime. Note that the ninepoint checkers are not very effective in this blockade (the threepoint is made; offensive points six apart are inefficient), they are more like builders for the fourpoint. That open fourpoint is the weakest part, but White will have a hard time making it.

Red still has some backcheckers to bring around. White's offense isn't much now, but it's a good start with the fivepoint made, builders well placed, also on the midpoint. In a few rolls, White might have a pretty strong blockade herself!

Red has a good advantage in the race. This is not terribly important here, as White is so strongly blocked.

White will have some lasting winning chances from his twopoint anchor, but they're pretty low. Given the third backchecker and the current race situation, White's twopoint anchor game won't have great timing and White will often crunch his board while waiting for a shot, so that even a hit won't be a winner.

White's chances to turn this into something better are by moving up the defense to the fourpoint anchor, for better timing and a chance to hit Red in the outfield. But that needs a specific good roll for White and simply won't happen often.

A stronger plan is for White to try and contain at least one of Red's backcheckers, form a counter-blockade and hope that Red is forced to break up something upfront eventually.

Last but not least, White can hope for a backgame, which might have good timing if it's the 23-21 (2-4) variety. The 24-23 (1-2) one will give plenty of shot chances, but is very hard to time, so White might be crunched by the time he hits and not always win after a hit. Still, better than just a 23pt game for White. Of course, White needs a fourth checker sent back quickly to have a go at a backgame at all!

Given all of the above, the 6-2 move here becomes a lot clearer.

[close]

[PersianLord]

Good instructive position, PL!

Spoiler

This is a good position to analyze even without the specific roll.

The matchscore means this is basically a DMP game, where only single wins are important. The exception is White winning a backgammon for the match, but that's rare from the starting position and even rarer from here! Safe to ignore this, and just look at single wins.

DMP games make certain game plans more attractive; on the defense, there is no fear of a (back)gammon loss anymore, so deep anchor games and backgames are more attractive. You can stay back as long as you wish, for that last ditch shot.

The board. Red has pinned down 3 of White's checkers behind a very strong blockade, which might turn into a full 6-prime. Note that the ninepoint checkers are not very effective in this blockade (the threepoint is made; offensive points six apart are inefficient), they are more like builders for the fourpoint. That open fourpoint is the weakest part, but White will have a hard time making it.

Red still has some backcheckers to bring around. White's offense isn't much now, but it's a good start with the fivepoint made, builders well placed, also on the midpoint. In a few rolls, White might have a pretty strong blockade herself!

Red has a good advantage in the race. This is not terribly important here, as White is so strongly blocked.

White will have some lasting winning chances from his twopoint anchor, but they're pretty low. Given the third backchecker and the current race situation, White's twopoint anchor game won't have great timing and White will often crunch his board while waiting for a shot, so that even a hit won't be a winner.

White's chances to turn this into something better are by moving up the defense to the fourpoint anchor, for better timing and a chance to hit Red in the outfield. But that needs a specific good roll for White and simply won't happen often.

A stronger plan is for White to try and contain at least one of Red's backcheckers, form a counter-blockade and hope that Red is forced to break up something upfront eventually.

Last but not least, White can hope for a backgame, which might have good timing if it's the 23-21 (2-4) variety. The 24-23 (1-2) one will give plenty of shot chances, but is very hard to time, so White might be crunched by the time he hits and not always win after a hit. Still, better than just a 23pt game for White. Of course, White needs a fourth checker sent back quickly to have a go at a backgame at all!

Given all of the above, the 6-2 move here becomes a lot clearer.

[close]

This is the kind of analysis I appreciate the most. Through, constructive and educative. Thanks Zorba. 

[sixty_something]

PL, nice work on your numerous problems and great comments by you and Zorba on this one in particular .. when i first started these posts, i experimented with several different styles .. the one i settled on includes the board image in the Poll question itself making it possible to see the position, question, and answers at the same time .. if you'd like to try that use something like this code as your Poll question:

Code Select Expand

[img]http://www.isarapix.com/pix84/1201822591.png[/img] [size=13pt]  WHITE, facing a backgame ahead 2-1 in a 5 pointer, tries to win the point with a bluff.  [b]WHITE to play. What is best?

the code above comes from the last problem i posted, Cube 109 - Cube against backgame? .. you'll see in the associated post that i also attached an image of the problem (since the imgage file is stored elsewhere), an associated text file with GNUbg analysis as an answer, and the Position and Match ID for entry into GNUbg or Snowie. if desired

we decided long ago to NOT insist on a "standard" problem style or attempt to enforce one .. so, any style is most welcome .. i just thought i'd offer this option to you as it is not self-evident how to display the board and position within a Poll question .. i've used IsaraPIX, a free service, to upload and store images and have been most satisfied with it

thanks again for your many problem posts and keep them coming .. i have collected a few to add soon myself - one an espeically interesting cube problem in a match with socksey

[PersianLord]

PL, nice work on your numerous problems and great comments by you and Zorba on this one in particular .. when i first started these posts, i experimented with several different styles .. the one i settled on includes the board image in the Poll question itself making it possible to see the position, question, and answers at the same time .. if you'd like to try that use something like this code as your Poll question:

Code Select Expand

[img]http://www.isarapix.com/pix84/1201822591.png[/img] [size=13pt]  WHITE, facing a backgame ahead 2-1 in a 5 pointer, tries to win the point with a bluff.  [b]WHITE to play. What is best?

the code above comes from the last problem i posted, Cube 109 - Cube against backgame? .. you'll see in the associated post that i also attached an image of the problem (since the imgage file is stored elsewhere), an associated text file with GNUbg analysis as an answer, and the Position and Match ID for entry into GNUbg or Snowie. if desired

we decided long ago to NOT insist on a "standard" problem style or attempt to enforce one .. so, any style is most welcome .. i just thought i'd offer this option to you as it is not self-evident how to display the board and position within a Poll question .. i've used IsaraPIX, a free service, to upload and store images and have been most satisfied with it

thanks again for your many problem posts and keep them coming .. i have collected a few to add soon myself - one an espeically interesting cube problem in a match with socksey

Thanks for the kind words.

About the style, I'm used to my style and I think it's good.

Regards

[Zorba]

I didn't mention the actual move in my last post, partly on purpose. 24/18 is clear from the reasons I gave. How to play the two is much less clear: 13/11 is very safe, but leaves you with a stripped position and only one spare to play freely (although the ninepoint can be seen as two spares/builders here). 9/7 starts bringing more builders into play, for making the important fourpoint, but leaves a relatively safe blot on the ninepoint, and a direct 1-shot for opponent on your midpoint.

I'd call it a "very safe" vs. "somewhat bold" move decision here. It is only somewhat bold; getting either blot hit here is not such a big deal, because the blockade is so strong. You figure to have time to enter and get around again.

Your strong position and White's weak board might indicate a bold move. On the other hand, White has three backcheckers compared to your (quasi-)anchor on the barpoint, which is an argument for a safe move. The fact that gammon wins don't help Red probably also makes the bold move a bit less attractive.

I voted for 9/7 but was far from sure. 13/11 does better in the rollout, but 0.03 is not much.

Since 9/7 might lead to more complicated positions, giving White more chances to make mistakes, I'd still play it against weaker players. But expert vs. expert, 13/11 seems to be the play here.

Here is a high settings rollout result:

    1. Rollout          24/18 13/11                  Eq.:  +0,442
        72,4%  36,6%   9,6% -  27,6%   4,7%   0,2% CL  +0,442
      [  0,3%   1,1%   0,8% -   0,3%   0,2%   0,0% CL   0,006]
        Full cubeless rollout (trunc. at one-sided bearoff) with var.redn.
        648 games, Mersenne Twister dice gen. with seed 835914028 and quasi-random dice
        Play:  2-ply cubeless prune
        keep the first 0 0-ply moves and up to 8 more moves within equity 0,06
        Skip pruning for 1-ply moves.
        Cube: 2-ply cubeful prune
    2. Rollout          24/18 9/7                    Eq.:  +0,412 ( -0,030)
        71,0%  39,7%  11,7% -  29,0%   5,8%   0,2% CL  +0,412
      [  0,4%   0,9%   0,8% -   0,4%   0,2%   0,0% CL   0,007]
        Full cubeless rollout (trunc. at one-sided bearoff) with var.redn.
        1296 games, Mersenne Twister dice gen. with seed 835914028 and quasi-random dice
        Play:  2-ply cubeless prune
        keep the first 0 0-ply moves and up to 8 more moves within equity 0,06
        Skip pruning for 1-ply moves.
        Cube: 2-ply cubeful prune
    3. Rollout          24/22*/16                    Eq.:  +0,331 ( -0,111)
        67,0%  42,9%  19,7% -  33,0%   3,6%   0,4% CL  +0,331
      [  0,8%   2,1%   2,3% -   0,8%   0,5%   0,1% CL   0,016]
        Full cubeless rollout (trunc. at one-sided bearoff) with var.redn.
        144 games, Mersenne Twister dice gen. with seed 835914028 and quasi-random dice
        Play:  2-ply cubeless prune
        keep the first 0 0-ply moves and up to 8 more moves within equity 0,06
        Skip pruning for 1-ply moves.
        Cube: 2-ply cubeful prune
    4. Rollout          18/10                        Eq.:  +0,328 ( -0,114)
        66,9%  40,1%  16,0% -  33,1%   7,2%   0,3% CL  +0,328
      [  0,9%   1,9%   1,8% -   0,9%   0,5%   0,1% CL   0,018]
        Full cubeless rollout (trunc. at one-sided bearoff) with var.redn.
        216 games, Mersenne Twister dice gen. with seed 835914028 and quasi-random dice
        Play:  2-ply cubeless prune
        keep the first 0 0-ply moves and up to 8 more moves within equity 0,06
        Skip pruning for 1-ply moves.
        Cube: 2-ply cubeful prune
    5. Rollout          24/22* 13/7                  Eq.:  +0,326 ( -0,116)
        66,3%  45,1%  23,3% -  33,7%   4,9%   0,0% CL  +0,326
      [  1,1%   1,9%   2,3% -   1,1%   0,4%   0,6% CL   0,023]
        Full cubeless rollout (trunc. at one-sided bearoff) with var.redn.
        216 games, Mersenne Twister dice gen. with seed 835914028 and quasi-random dice
        Play:  2-ply cubeless prune
        keep the first 0 0-ply moves and up to 8 more moves within equity 0,06
        Skip pruning for 1-ply moves.
        Cube: 2-ply cubeful prune

[adrian]

I missed your BG problems. Welcome back !