Game 3, move 24, 25 and 26: Forum 4-2

[diane]

Ok, we had a flurry of activity after moving our 15-8, all pretty much obvious, so I nexted them....

Firstly after we moved 15/8, rkb rolled 2-1, and I took the liberty of assuming his hit, 20/17*

7zYTEADntgoAAw:AQGlACAAAAAA

Forum then rolled a lifesaving 6-2, which not only got us off the bar, but hit a second checker...Bar 19*/17*

57YKIALvNgMIQA:QQmrACAAAAAA

rkb danced with 4-1

7zYDSADnNgGIYA:AQGmACAAAAAA

Now Forum (blue) to move 4-2

5zYBiGDvNgNIAA:QQmxACAAAAAA

[vikingblood80]

Spoiler

Well about the hit..I'm not sure if its really clear..at least for rkb with access to the cube he could double us out after a possible dance.At DMP I'm pretty sure its the correct move but as here Gammon losses are still an issue for rkb.well I'm not sure.

Now to our 4-2:

Want to get our checkers home and do not want to seperate them.
Since 5-5 is the comeback roll for rkb we dont want to put single spares on the 13 or 10 point.

This only leaves 17/13 15/13 and 17/11 as possibilities. May be our chance of hitting that blot on the 8 are higher when making the 13-point, I feel (that means I haven't counted) that 17/11 will bring us home more easily especially with our opp having 2 on the bar.

[close]

[ah_clem]

Spoiler

We're in good shape here.  Probably the most important thing is to play anti-joker, so don't leave a checker on the 15.  Only 15/9 and 17/13 15/13 accomplish this.  Hitting a third blot would increase our gammon chances, and we're more likely from 5 points away than one point away.

And now I've probably given this more thought than it deserves. 

17/13 15/13

[close]

[ah_clem]

Spoiler

Since 5-5 is the comeback roll for rkb we dont want to put single spares on the 13 or 10 point.

This only leaves 17/13 15/13 and 17/11 as possibilities.

How does that leave 17/11 as a possibility?  15/9 is the other possibility.

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[diane]

Spoiler

How does that leave 17/11 as a possibility?  15/9 is the other possibility.

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Agree, maybe take another look, viking.

[diane]

Spoiler

Well about the hit..I'm not sure if its really clear..at least for rkb with access to the cube he could double us out after a possible dance.At DMP I'm pretty sure its the correct move but as here Gammon losses are still an issue for rkb.well I'm not sure.

[close]

Spoiler

 don't say that, I have been paranoid about nexting anything - but gnu certainly thought anything else was quite wrong.  The trouble is, that what happened next may cloud this one a bit.

[close]

[roadkillbooks]

OUCH....what a bad shake.  Its hard for me to see the move in retrospect to see what I would have done.  Of course seeing the situation like this i say that I clearly would have not hit but I don't know.  I have been eschewing hits while building my board.  I think I even eschewed a hit on that same point with another 3-1.  I have also commented about not leaving blots all over the board. With hitting the potential for losing a gammon is quite high...if i don't hit Im conceding some equity but I surely wont lose a gammon.  I think that w/out hitting now Im probably around 25%.  I assume this by looking at the non hit position, imagine a double and it feel like a take.  Racing chances is probally around 8%, and I will most likely get another (at least indirect shot).  Almost all holding positions with a 5 point anchor and immediate shot potential with a strong board are takes. Gammons are a major part of this position as is match score.  If I hit my chances are:  lets assume hits are loses and MOST of those are gammons , dances are wins, and coming out on the 2 and not hitting split.  There are 15 hits, 5 2's that don't hit, that leaves 16 dance numbers.  If all hits were gammons it would be:
My loses would be
15 x 4 (hit gammons)=60, 3 x 2 (give forum 3 of 5 wins with a non-hitting 2s) =6  60+5=66

My wins are
(16 x 2)+ (2 x 2)=36
66-36=30 points lost

Not hitting

is 27 x 2=54 (me losing race 75% of time)
9 x 2= 18 (me winning 25%)

54-18=36 points lost

So based on that number I would have hit..

Now this does leave other things unresolved and whether or not I would have either erred or not. But I don't think this was a next..a 6 point difference but what if im not calculting the non-hitting 2's? if i only win 1 of five....it is onnly a point point difference or a minor error.

but anyway.....i don't like my predicament anymore   

roadkillbooks

[ah_clem]

OUCH....what a bad shake.  Its hard for me to see the move in retrospect to see what I would have done. 

Well, according to gnubg none of the other moves are even close, although I can't say it's completely obvious to me. 

Maybe it's not a NEXT, but at least be thankful that diane was moving for you instead of me.  (c:



    1. Rollout          20/17*                       Eq.:  -0.338
       0.465 0.120 0.006 - 0.535 0.282 0.013 CL  -0.402 CF  -0.338
      [0.001 0.002 0.001 - 0.001 0.002 0.001 CL   0.005 CF   0.006]
    2. Rollout          8/6 7/6                      Eq.:  -0.464 ( -0.126)
       0.243 0.011 0.000 - 0.757 0.016 0.000 CL  -0.530 CF  -0.464
      [0.001 0.001 0.000 - 0.001 0.001 0.000 CL   0.002 CF   0.003]
    3. Rollout          8/6 3/2                      Eq.:  -0.503 ( -0.165)
       0.236 0.013 0.000 - 0.764 0.027 0.000 CL  -0.561 CF  -0.503
      [0.001 0.002 0.000 - 0.001 0.001 0.000 CL   0.002 CF   0.004]       
    4. Rollout          7/6 3/1                      Eq.:  -0.513 ( -0.175)
       0.229 0.009 0.000 - 0.771 0.018 0.000 CL  -0.561 CF  -0.513
      [0.001 0.001 0.000 - 0.001 0.001 0.000 CL   0.002 CF   0.004]
        Full cubeful rollout with var.redn.
        1296 games, Mersenne Twister dice gen. with seed 868041210 and quasi-random dice
        Play: 0-ply cubeful prune [expert]
        Cube: 0-ply cubeful prune [expert]

[diane]

I can go back...it will of course give a completely different outcome, but if rkb feels that he would like to reason out a not-hit [which seems to be already done], then I will take it back to his 2-1 and let the game go from his choice.  Let me know.

I don't want this to get contentious, it is meant to be fun.

[roadkillbooks]

No..I probally would of it.

When I said "ouch bad shake"..i wasn't talking about the next.  I was talking about the lousy situation I am in now.  While clearly -.12 is a blunder and "NOT even close"....the nature of the situation is one the still has to be made.  Its not a stupid play not to hit...just overly timid.  I most likely would have it.  I was basically saying that I might have made the blunder not to hit...

that is of coursr not possible to do now becasue if we went back I would hit because I have spent more time figuring it out and I just saw the gnu numbers..which reflect fairly closely what I estimated out.  6 points in 36 would be  a -.167 (i think), 4 points would be -.11 .............

So lets just go and roll my a 5 fast and prove me wrong that most of the hits are not gammons.



roadkillbooks

[diane]

ok, thanks - I have angsted most of the night over this one - I am definitely waiting now - however likely your move might seem  

There is quite a close vote on this one - and we have 4 voters missing [or thereabouts], so I will give them a chance to have their say.

[vikingblood80]

Agree, maybe take another look, viking.

Ah..thougt he had 3 on the bar...then of course no blot on 10,13 and 15.

[Zorba]

Have to agree that rkb's 2-1 was not a next, actually a pretty tough problem for human players to solve over the board as it involves weighing wins against losing gammons, at a lop-sided matchscore. Good analysis by rkb. With the difference between the moves a little over 0.1 according to GnuBG, it's far from obvious every good backgammon player would have hit here. After all, even world class players makes blunders at the ~0.1 level every now and then. That said, I'd guess most players would end up hitting here, as it's such an obvious road to turn the game around right away. So no harm done here I'm pretty sure

On to our 4-2 move:

Spoiler

This game is almost in our pocket and we have high gammon chances too. The best scenario is to pick up both other blots and close the fivepoint, for a near sure gammon win. Pick'n'pass on the fivepoint could also be quite effective to raise our gammon wins. 17/11 looks best for an aggressive approach: 3's and 7's hit the outfield blot, 6's and 10's may hit on the 5pt.

There's however still one risk of losing this game suddenly: a hitting 5-5 by rkb. To avoid turning this roll into a big joker for rkb, we should try not to leave blots at our 10, 13 and 15pts. 17/13 15/13 is pretty good as it even blocks this 5-5 partly, making it a bit ugly for rkb to play. It gives us 5's to hit the blot, pretty good, and perhaps 8's (4-4!) to hit on our 5pt. It keeps both outfield checkers close together, usually the best way to bring them around (although putting them on the same point is usually not optimal). Also, the 13pt is not in direct shot range of a potential anchor by rkb, this might help us if he enters quickly.

Compare to 15/9, which leaves 1's to hit (and 9's), a few more shots but worse checker placement: the two outfield checkers are now furthest apart, and the front checker in direct range of rkb's potential anchor. If rkb enters quickly, the backchecker could get into trouble sometimes as we'd first save the other checker.

Conclusion: 17/11 is too risky since the 5-5 risk can be eliminated smoothly by either of the other plays. Between those two, I have a slight preference for 17/13 15/13 for the reasons stated above, although I'm not particurlarly fond of putting both on the same point in situations like this. Here, however, making the point makes rkb's 5-5 even worse, that should be worth something.

[close]

[adrian]

That said, I'd guess most players would end up hitting here, as it's such an obvious road to turn the game around right away.

Never do what the enemy expects. 

[Zorba]

GnuBG says...

Spoiler

Close decision, first two moves way too close to call.

    1. Rollout          17/13 15/13                  Eq.:  +2,0203
        95,23  74,17   3,42 -   4,77   0,22   0,00 CL  +2,0322 CF  +2,0203
      [  0,05   0,10   0,07 -   0,05   0,02   0,12 CL   0,0021 CF   0,0022]
        Full cubeful rollout with var.redn.
        3888 games, Mersenne Twister dice gen. with seed 866958214 and quasi-random dice
        Play:  2-ply cubeful prune [world class]
        keep the first 0 0-ply moves and up to 12 more moves within equity 0,16
        Skip pruning for 1-ply moves.
        Cube: 2-ply cubeful prune [world class]
    2. Rollout          15/9                         Eq.:  +2,0173 ( -0,0030)
        95,29  73,76   3,52 -   4,71   0,13   0,00 CL  +2,0295 CF  +2,0173
      [  0,05   0,10   0,07 -   0,05   0,02   0,00 CL   0,0020 CF   0,0022]
        Full cubeful rollout with var.redn.
        3888 games, Mersenne Twister dice gen. with seed 866958214 and quasi-random dice
        Play:  2-ply cubeful prune [world class]
        keep the first 0 0-ply moves and up to 12 more moves within equity 0,16
        Skip pruning for 1-ply moves.
        Cube: 2-ply cubeful prune [world class]
    3. Rollout          17/11                        Eq.: +2,0004 ( -0,0199)
        94,15  74,14   3,83 -   5,85   0,38   0,00 CL  +2,0148 CF  +2,0004
      [  0,05   0,10   0,08 -   0,05   0,07   0,01 CL   0,0021 CF   0,0023]
        Full cubeful rollout with var.redn.
        3888 games, Mersenne Twister dice gen. with seed 866958214 and quasi-random dice
        Play:  2-ply cubeful prune [world class]
        keep the first 0 0-ply moves and up to 12 more moves within equity 0,16
        Skip pruning for 1-ply moves.
        Cube: 2-ply cubeful prune [world class]

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