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The serious thing about this position is the 4 pips difference After black play. The bots sometimes overstimates this advantage and so one has to discard istant the running move 21/13(2). So one has to keep contact, even if in practice a move like that passes white the responsability to estricate the back anchor: a not so easy job for a mortal. With less than 4 pips advantage i think that the running move should Be optimal because of the simple play it leads. The bots like home board points also, and a move like 8/4(2) is about forced. So you has not really a choiche here. With less than 4 point gap almost any move is good imo

Quote

04-13-2015 , 12:57 PM

#127

uberkuber

veteran

Join Date: Jul 2009 Posts: 3,032

Grunch.
Although it seems counterintuitive because Black is trailing, I'm tempted to (almost) equalize the race and disengage with 21/13 (2), letting White having problems with his back checkers.

Quote

04-13-2015 , 01:07 PM

#128

Fllecha

journeyman

Join Date: Mar 2010 Posts: 321

Quote:

Originally Posted by uberkuber

Grunch.
Although it seems counterintuitive because Black is trailing, I'm tempted to (almost) equalize the race and disengage with 21/13 (2), letting White having problems with his back checkers.

Put in your opponent shoes: you have to disengage the high anchor and your next move you almost always give up the midpoint, 6-1 is a disaster, while black has only to clear the midpoint and almost any roll is good because of the landing spot in the 8 point. Ok you dont have the bar but Who cares, practically you have easy game and with a normal rolling you keep the game playable. Isn't it? No: there is NO WAY that the bot Will agree with this decision: as said above ANY trailing difference leads bot to keep men back and that why this game is difficult to understand SOMETIMES with Logic.

Quote

04-14-2015 , 01:22 AM

#129

bleep69

grinder

Join Date: Sep 2008 Posts: 483

Quote:

Originally Posted by Fllecha

... that why this game is difficult to understand SOMETIMES with Logic.

The danger is in applying logic without understanding the rationale behind what it is you are trying to do, and this is what leads me astray every single time! It's misunderstanding the basics.

Quote

04-14-2015 , 07:23 AM

#130

yogiman

adept

Join Date: Jun 2012 Posts: 784

This is a dummy problem, with the wrong move being 21/13(2) and I am surprised but also pleased that it provoked some discussion.

White - Pips 103

Code:

    1. 21/17(2) 8/4(2)              Eq.:  +0,265
       0,568 0,108 0,003 - 0,432 0,041 0,001 CL  +0,205 CF  +0,265
      
    2. 21/13 8/4(2)                 Eq.:  +0,250 ( -0,015)
       0,553 0,180 0,005 - 0,447 0,058 0,001 CL  +0,231 CF  +0,250
      
    3. 21/17(2) 13/9(2)             Eq.:  +0,219 ( -0,046)
       0,561 0,076 0,001 - 0,439 0,024 0,001 CL  +0,174 CF  +0,219
     
    4. 21/13(2)                     Eq.:  +0,051 ( -0,214)
       0,515 0,023 0,000 - 0,485 0,011 0,000 CL  +0,042 CF  +0,051

The crucial thing in this problem is the throwing of 6's. Both parties hope that the opponent will be the first one to throw that potentially fatal 6. The probability of not throwing a 6 is 70%, and after two times in a row having to play within the homeboard (50%), it is very well possible that one has to break a point with a 5. Something else is that in case you hit, you don't want to have a homeboard that is wrecked. This makes flexibility important.

Ignoring 21/13 8/4(2) for the sake of simplicity, there are three options:

keeping most contact and least flexibility with 21/17(2) 8/4(2)
keeping the least contact and most flexibility with 21/13(2)
compromising with 21/17(2) 13/9(2)

So you run to the 13-point in case you are ahead, because you have better racing chances and a worse timing in the waiting battle.
Black is still behind after the roll, so he should not run. Observing both homeboards after playing 21/17(2) 8/4(2) both have about the same flexibility in their homeboard. Only from the rollout I can tell that it is likely that he should have played the compromising 21/17(2) 13/9(2) if it would not be so that he can strengthen his homeboard with 8/4(2).

Here I have put some changes so that black is 5 pips ahead after the roll:

White - Pips 107

Black - Pips 118

Code:

    1. 21/17(2) 13/9(2)             Eq.:  +0,266
       0,579 0,073 0,002 - 0,421 0,034 0,001 CL  +0,197 CF  +0,266
      
    2. 21/17(2) 8/4(2)              Eq.:  +0,177 ( -0,089)
       0,548 0,100 0,003 - 0,452 0,062 0,001 CL  +0,137 CF  +0,177
     
    3. 21/13(2)                     Eq.:  +0,163 ( -0,102)
       0,551 0,018 0,000 - 0,449 0,015 0,000 CL  +0,107 CF  +0,163

As it is white's turn now, those 5 pips make it still not appropiate to run. The best move here is to keep some lesser contact, as a concession for having less flexibility in the homeboard in relation to white's.

PS Please correct me if I am wrong.

Quote

04-15-2015 , 02:55 AM

#131

Taper_Mike

adept

Join Date: Sep 2009 Posts: 1,030

For a "dummy," this turned out to be a pretty nice problem. I think I would have played 21/17(2) 13/9(2) OTB, with the idea that I would win the timing battle.

After seeing the rollout, it is clear that making the 4pt is best. That gives Black a 5-point board, something that White will probably never have. In the outfield, both players will be out of time, but White has to roll first. In addition, if Black is hit, he may easily enter and escape. If, on the other hand, White dances against a 5-point, it is probably lights out for him.

Mike

Quote

04-16-2015 , 05:35 AM

#132

yogiman

adept

Join Date: Jun 2012 Posts: 784

Position ID: vJ9xAABmGwgwNg Match ID: UqkOABAAAAAE

White - Pips 75

Black - Pips 180
Black to Play 5-3
Created with www.BGdiagram.com

Quote

04-16-2015 , 06:41 AM

#133

Kamba

enthusiast

Join Date: Feb 2015 Posts: 93

I must admit I am clueless here.

If i move off the 12 point I am thinking that my next throw would leave me breaking up my back game.

So I would play: 23/15

I don't think it weakens my position too much (unless he throws 2 1, in which case I would be very sad).

Quote

04-16-2015 , 07:17 AM

#134

Fllecha

journeyman

Join Date: Mar 2010 Posts: 321

I simply keep my 3 super anchors and play 12/4 and i watch my opponent roll a brick that leaves shots every where

Quote

04-16-2015 , 08:19 AM

#135

bleep69

grinder

Join Date: Sep 2008 Posts: 483

Another tough one if you don't quite understand the theory! Which I don't. With that in mind, here goes...

12/4 seems so obvious that I'm reluctant to pick it. OTB this would probably be my move though. The only other possibilities are 23/15 and 20/12, and I can't quite see the logic in either of those. Of the 2, 20/12 only leaves 44 which hits and covers, any other hit should give us a chance to hit back, and now it's a bit tricky for white to bear in. Added to that, we have some good timing with the 2 blots on the 12 point, so after all that, I guess my move is 20/12

Quote

04-16-2015 , 09:23 AM

#136

uberkuber

veteran

Join Date: Jul 2009 Posts: 3,032

If you're going to play 20/12, why not play 20/15 12/9? You'll probably need your 3-pt soon I guess.

Quote

04-16-2015 , 01:05 PM

#137

Robertie

old hand

Join Date: May 2004 Posts: 1,954

Right now White's 4s are blocked, but if I open up the 20-point his 4s become playable, and some are really bad. However, I don't want to be hit if I can avoid it, so my play looks like 20/15 20/17.

Now 6-4, 5-4, and 4-3 expose two blots and I have my whole roll to play. Not only will I have 1s, 3s, and 4s to hit, but since I'm not on the bar I also pick up 6-2 and 5-2 as indirects.

Quote

04-17-2015 , 01:36 AM

#138

bleep69

grinder

Join Date: Sep 2008 Posts: 483

Quote:

Originally Posted by uberkuber

If you're going to play 20/12, why not play 20/15 12/9? You'll probably need your 3-pt soon I guess.

That's a fine question, and one I wish I had thought to ask myself. Not looking at all the possibilities seems to be a very limiting factor in my play.

Quote

04-17-2015 , 10:55 AM

#139

Taper_Mike

adept

Join Date: Sep 2009 Posts: 1,030

Grunch. This is my thinking before reading the posts of others.

Black can hang on to all three anchors for one more turn, but only if he plays 12/4. After that, he will be forced to weaken his front position if he rolls 44, 41, 22, or 11 on the following turn. In addition, rolling 31 or 21 would probably mean playing 20/17. That would give White the option of hitting loose outside when he rolls an awkward ace.

Suppose Black were to give up one of his anchors. Which one should it be, the 20pt or the 23pt? My preference is to keep the two rear points, and break the most advanced anchor on the 20pt. Holding onto the back two anchors maximizes contact.

There are two ways to break the 20pt, 20/12 and 20/15 12/9. There may not be much difference between the two, but I like the latter. It keeps the outfield checkers diversified.

Let’s check White’s rolls to see the difference between keeping the 20pt and abandoning it. The only rolls that play differently are 11, 22 and any roll with a 4.

Better if keep 20pt
Avoid point-on-head when White rolls: 44, 22, and 11
Avoid pick and pass when White rolls: 42 and 41

Better if break 20pt
White leaves a blot: 64, 54, 43

Note that if Black breaks the 20pt, and White rolls one of the good numbers that allow him to safely hit or make that point, Black will still have plenty of life. His two other anchors mean he should enter quickly, and, in case he does not, his checker on the bar might mean getting a triple shot if White leaves a blot.

It looks like it’s time to go.

20/15, 12/9

Late edit: Having now read the posts of others, I see that I did not consider Bill's play of 20/17 20/15. White would have aces to hit outside, but his 4s would play worse for him (as explained by Bill).

Mike

Last edited by Taper_Mike; 04-17-2015 at 11:07 AM.

Quote

04-17-2015 , 12:07 PM

#140

yogiman

adept

Join Date: Jun 2012 Posts: 784

Code:

     1. 20/17 20/15                  Eq.:  +0,100
       0,548 0,073 0,003 - 0,452 0,243 0,052 CL  -0,124 CF  +0,100
      
    2. 20/17 12/7                   Eq.:  +0,063 ( -0,036)
       0,544 0,066 0,003 - 0,456 0,254 0,058 CL  -0,155 CF  +0,063
      
    3. 20/15 12/9                   Eq.:  +0,062 ( -0,038)
       0,544 0,064 0,002 - 0,456 0,252 0,056 CL  -0,153 CF  +0,062
    
    4. 20/12                        Eq.:  +0,052 ( -0,048)
       0,540 0,063 0,002 - 0,460 0,252 0,055 CL  -0,162 CF  +0,052
      
    5. 12/4                         Eq.:  -0,066 ( -0,166)
       0,505 0,054 0,002 - 0,495 0,270 0,053 CL  -0,256 CF  -0,066

Rollouts have shown me that playing from the 20-point is only really profitable when white occupies the 15 or 16-point, and just arbitrary when white occupies the 14, 17 and 18 points. In case of the 14-point it is ofcourse unwise to play 20/17 20/15, and if the left checker on the 20-point is hit there are less indirect shots from the bar.

Also moving the white checker from 16w to 19 makes departing from the 20-point arbitrary, and this drop in relative value is mainly because the two checkers can be played without leaving a third behind.

Even when 16w and 19w both contain several builders, departing from the 20-point is a lot better:

Code:

    1. 20/15 12/9                   Eq.:  -0,168
       0,481 0,035 0,001 - 0,519 0,279 0,060 CL  -0,340 CF  -0,168
     
    2. 12/4                         Eq.:  -0,259 ( -0,091)
       0,450 0,028 0,001 - 0,550 0,293 0,056 CL  -0,420 CF  -0,259

This is ofcourse not because leaving the 20-point is so strong, but because moving up the lonely checker is so weak. The value of departing from the 20-point diminishes when the lonely checker has to move less up:
checker on 12-point:

Code:

     1. 20/17 20/15                  Eq.:  +0,100
       0,548 0,073 0,003 - 0,452 0,243 0,052 CL  -0,124 CF  +0,100
      
    2. 12/4                         Eq.:  -0,066 ( -0,166)
       0,505 0,054 0,002 - 0,495 0,270 0,053 CL  -0,256 CF  -0,066

checker on 13-point:

Code:

    1. 20/17 20/15                  Eq.:  +0,100
       0,551 0,074 0,003 - 0,449 0,246 0,052 CL  -0,119 CF  +0,100
      
    2. 13/5                         Eq.:  -0,030 ( -0,130)
       0,515 0,060 0,002 - 0,485 0,265 0,055 CL  -0,229 CF  -0,030

Position ID: vJ9xAABmGxAwNg Match ID: UokOABAAAAAE

checker on 14-point:

Code:

    1. 20/17 20/15                  Eq.:  +0,088
       0,545 0,072 0,003 - 0,455 0,246 0,053 CL  -0,134 CF  +0,088
    
    2. 14/6                         Eq.:  -0,052 ( -0,139)
       0,511 0,057 0,002 - 0,489 0,267 0,056 CL  -0,241 CF  -0,052

Position ID: vJ9xAABmGyAwNg Match ID: UokOABAAAAAE

checker on 15-point:

Code:

    1. 20/17 20/15                  Eq.:  +0,097
       0,551 0,071 0,003 - 0,449 0,246 0,054 CL  -0,124 CF  +0,097
     
    2. 15/7                         Eq.:  +0,016 ( -0,081)
       0,532 0,057 0,002 - 0,468 0,262 0,056 CL  -0,195 CF  +0,016

Position ID: vJ9xAABmG0AwNg Match ID: UokOABAAAAAE

There is a 50% drop in the relative value of 20/17 20/15 (0,081 vs 0,166) when the checker can be played outside the homeboard in comparison to the original position. In his book “Modern Backgammon”, Bill Robertie warns against semi-killing a checker, but in an open field like in this position, I can't see so much harm. I also doubt Taper_Mike's perspective about the bad dices, because white will be next turn, and it is not likely that much will be left of white's outside point. 3-point backgames are not the bot's strongest point, but for convenience we presume that the bot is right. The suggestion is maybe that the option of creating a point in direct range of the 3point-gap is important. And another thing that is important is to have two free checkers close together in order for better containment of a hit white checker.

In order to save energy and not to make too much fuss about little I propose to play always from the 20-point in these kinds of positions.

PS Commentary and criticism are welcome

Quote

04-17-2015 , 01:53 PM

#141

yogiman

adept

Join Date: Jun 2012 Posts: 784

Quote:

I also doubt Taper_Mike's perspective about the bad dices, because white will be next turn, and it is not likely that much will be left of white's outside point.

DISCLAIMER
Apologizes, after close inspection this turns out to be a blunt statement. Only white dice numbers 52, 62, 53, 63, 65 leave a blot on white's 16-point, and 33,55 and 66 clear the space. That's about 65% of "unfavourable positions" for black after white's turn. So bad numbers are some issue for black after white's dices. This weakens my statement:"The suggestion is maybe that the option of creating a point in direct range of the 3point-gap is important".

Last edited by yogiman; 04-17-2015 at 02:04 PM.

Quote

04-18-2015 , 01:44 PM

#142

yogiman

adept

Join Date: Jun 2012 Posts: 784

Position ID: uL0jAAYbm3kAIA Match ID: cIkJAAAAAAAE

White - Pips 119

Black - Pips 108
Black to Play 3-2
Created with www.BGdiagram.com

Quote

04-18-2015 , 02:34 PM

#143

Taper_Mike

adept

Join Date: Sep 2009 Posts: 1,030

Let’s take a look at White’s point-making rolls.

Make his 3pt (a.k.a. Black’s 22pt): 43, 41, 33, 31
Make his 2pt (a.k.a. Black’s 23pt): 54, 52, 44, 42, 22
Make his 1pt (a.k.a. Black’s 24pt): 65, 63, 55, 53

Does Black want to be on the 24pt if White fills in a point in front of him? Probably not. Right now, Black has the better board. If he advances to the 22pt, White will surely attack, but White has only the 7 point-on-head rolls mentioned above. In other variations, Black will have plenty of returns.

I am inclined to move the runner into escape position, and duke it out now, before White can improve his position. I don’t like volunteering a blot on the bar point, but staying back is just as perilous.

24/22, 10/7

Should White double after this play? Maybe yes, maybe no, but I would take if he does.

Mike

Quote

04-18-2015 , 03:05 PM

#144

Karol Szczerek

enthusiast

Join Date: Mar 2015 Posts: 92

24/22 10/7 looks natural. If opp makes 5-point block before we run, we are done. We have to fight while we have a stronger board and some flexibility on the other side for counter-attack. There are only 10 pointing numbers on the 22pt. It may look that the 10/7 trey is too much risk but 31, 33, 34 are duplicated on the other side of the board, and 35, 36, 32 aren't that bad, as we have plenty of returns.

We tend to remember bad beats, and we've all have been gammoned hard from this kind of positions with 2 blots to pick-up. It is the first picture that comes to mind after looking at this play - isn't it? But there's no place for such fear in BG. Playing too safe get's You nowhere. In fact You should do the opposite, and it's generally true for any hazard (or sorry - randomness-heavy) game: if You are loosing, You should take more risk than usual to try to turn things around.

The waiting play - 10/5 - leaves initiative to White, and keep his options open. He can use builders to build another inner point, he can attack on the 1pt. if he likes, or he can shuffle some checkers on the blockade. We are still stuck, with little chance to escape early. We have worse timing and will most probably break an outfield blocking point sooner than he does. He will have an option to run every roll, without much threat from our side. It just must be a blunder. After 24/22 10/7 he has to attack now, while it's still dangerous to him.

EDIT (sorry Mike, I had to correct You):
after 24/22 10/7 the rolls that points on our head:
31, 41, 43, 11, 22, 33, 44 = 10 rolls

Last edited by Karol Szczerek; 04-18-2015 at 03:16 PM. Reason: adding count of rolls that point on 22pt. after 24/22 10/7

Quote

04-18-2015 , 03:29 PM

#145

Taper_Mike

adept

Join Date: Sep 2009 Posts: 1,030

Quote:

Originally Posted by Karol Szczerek

Sorry Mike, I had to correct you. ):

After 24/22 10/7 the rolls that points on our head:
31, 41, 43, 11, 22, 33, 44 = 10 rolls

Thanks. I missed the doublets.

Mike

Quote

04-21-2015 , 03:46 AM

#146

yogiman

adept

Join Date: Jun 2012 Posts: 784

White - Pips 119

Black - Pips 108
Black to Play 3-2
Created with www.BGdiagram.com

Code:

    1. 24/22 10/7                   Eq.:  -0,319
       0,420 0,089 0,002 - 0,580 0,182 0,004 CL  -0,255 CF  -0,319
     
    2. 10/5                         Eq.:  -0,437 ( -0,118)
       0,380 0,060 0,001 - 0,620 0,110 0,003 CL  -0,294 CF  -0,437

Giving white extra building power by moving 19w to 20 doesn't change a lot:
Position ID: uLsjAAYbm3kAIA Match ID: cIkJAAAAAAAE

Code:

    1. 24/22 10/7                   Eq.:  -0,451
       0,382 0,070 0,002 - 0,618 0,185 0,005 CL  -0,354 CF  -0,451
     
    2. 10/5                         Eq.:  -0,552 ( -0,101)
       0,350 0,058 0,001 - 0,650 0,114 0,003 CL  -0,358 CF  -0,552

Neither by moving the outfield checker from 16w to 15:
Position ID: uL0TAAYbm3kAIA Match ID: cIkJAAAAAAAE

Code:

    1. Rollout          24/22 10/7                   Eq.:  -0,439
       0,391 0,084 0,001 - 0,609 0,205 0,005 CL  -0,342 CF  -0,439
     
    2. Rollout          10/5                         Eq.:  -0,544 ( -0,105)
       0,352 0,061 0,001 - 0,648 0,121 0,003 CL  -0,357 CF  -0,544

Even applying both changes together, just makes both moves a draw:

Code:

    1. 24/22 10/7                   Eq.:  -0,683
       0,343 0,088 0,003 - 0,657 0,236 0,005 CL  -0,463 CF  -0,683
     
    2. 10/5                         Eq.:  -0,686 ( -0,003)
       0,307 0,055 0,001 - 0,693 0,129 0,003 CL  -0,461 CF  -0,686

Both moves are even money. The rolls that point on white's head are 64, 63, 62, 61 – 43, 42, 41 - 32, 31 – 21 – 11, 22, 33, 44. That's 24 out of 36, and that is two thirds of the rolls. And he is almost surely to hit loose. You may wonder whether it is so bad for white to be hit. In case he is hit on his head, he will not be able to play high numbers, and is in a better condition to maintain his broken wall at the other side of the board. White has the same chance to slip through one of the holes, as black has to enter, and that's a little more than 50%. The rollout tells us that that the advantages and disadvantages cancel each other almost out.

Coming back to the original position. The worst thing that can happen is that white makes the point upon his head, though as said this can be put into perspective. And if white hits loose, black has 40% chance to hit back and to become a strong favorite, also because black has the better board and a pip advantage. The cubeless equity difference is 0,04, so a lot of merit of 24/22 comes from the cube. I suspect black has some weak passes and strong takes, and that is all I can say about it.

Quote

04-21-2015 , 08:25 AM

#147

yogiman

adept

Join Date: Jun 2012 Posts: 784

Quote:

I suspect black has some weak passes and strong takes, and that is all I can say about it.

I mean strong passes, passes which are not very far from too good to double for white. This is to keep you sharp.

Quote

04-22-2015 , 04:59 AM

#148

Taper_Mike

adept

Join Date: Sep 2009 Posts: 1,030

White - Pips 133

Black - Pips 168
Position 19. Black to Play 4-1

Unlimited game, no Jacoby, no beavers
XGID=--a---D-D---bD--Aebe--B---:0:0:1:41:0:0:0:0:10

Mike

Quote

04-22-2015 , 05:40 AM

#149

Kamba

enthusiast

Join Date: Feb 2015 Posts: 93

Tricky.

I would like to leave the guy on the 16 point. Let him break his mid point to hit me if he wants.

I would also like to slot the 5 point as my structure is looking terrible with all those towers. I need to start building something now.

So i guess i would play:

13/9 6/5

I may be totally off but I don't think I mind being hit, due to the fact that white is also looking a bit awkward.

Last edited by Kamba; 04-22-2015 at 05:46 AM.