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Move 104 - 2 checker bear off

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Offline don

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Move 104 - 2 checker bear off
« on: February 12, 2008, 10:48:01 PM »
I saw this during a FIBS match where O made the wrong move and reconstructed the position here... see next post for spoilers.

gnu position ID: DwAAAAoAAAAAAA
   gnu match ID: cIkkAAAAAAAA

« Last Edit: February 13, 2008, 04:07:12 AM by don »
So many string dimensions, so little space time...

FIBS Board backgammon forum

Move 104 - 2 checker bear off
« on: February 12, 2008, 10:48:01 PM »

Offline don

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Re: Move 104 - 2 checker bear off
« Reply #1 on: February 12, 2008, 10:59:12 PM »
This is basic backgammon and shows a situation where it's valuable to actually count the number of rolls that will bear off on O's next roll.  In this case:
Sorry but you are not allowed to view spoiler contents.
Here's a table of 2-man bearoff odds sorted in order of best/worst bear off:
Sorry but you are not allowed to view spoiler contents.

--
don
« Last Edit: February 13, 2008, 04:13:20 AM by don »
So many string dimensions, so little space time...

FIBS Board backgammon forum

Re: Move 104 - 2 checker bear off
« Reply #1 on: February 12, 2008, 10:59:12 PM »

Offline Hardy_whv

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Re: Move 104 - 2 checker bear off
« Reply #2 on: February 13, 2008, 07:07:38 AM »
I stopped counting moves in such situations. When you have to place two checkers to maximise your chances to bear them all off in the next roll, there is a principle that makes counting or moves obsolete.

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Hardy  B)
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Offline spielberg

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Re: Move 104 - 2 checker bear off
« Reply #3 on: February 13, 2008, 04:31:14 PM »
Hardy's right but I think his number is very slightly too low.

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If I'm right I shall be extremely proud - correcting Hardy is an event of some magnitude!

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Re: Move 104 - 2 checker bear off
« Reply #3 on: February 13, 2008, 04:31:14 PM »

Offline don

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Re: Move 104 - 2 checker bear off
« Reply #4 on: February 13, 2008, 07:47:38 PM »
Excellent comments from Hardy and ET (at least I learned something)!

After a Google or two, I can tell you that Thomas Koch (wintom) got the idea for the rule from a discussion at http://groups.google.com/group/rec.games.backgammon/browse_thread/thread/8a2b7015ac3ba4a2/9740ef2c7d4851be?lnk=gst&q=wintom+rule#  and it was called the rule of 2 or 3:
  • Rule of 2 or 3..." Play to have your last two pieces two or three pips apart and if that is not possible have them as close to 2 or 3 as possible"
  • Why didn't I ask the pros in the first place ;-)

Here's my previous chart, sorted by win then pip count to show why this rule works:
 points   OFF     FAIL     %    pip  separation

   1-1   36/36    0/36   1.00    2       0
   1-2   36/36    0/36   1.00    3       1

   1-3   34/36    2/36   0.94    4       2
   2-2   26/36   10/36   0.72    4       0

   1-4   29/36    7/36   0.81    5       3
   2-3   25/36   11/36   0.69    5       1

   1-5   23/36   13/36   0.64    6       4
   2-4   23/36   13/36   0.64    6       2
   3-3   17/36   19/36   0.47    6       0
   3-4   17/36   19/36   0.47    6       1
   1-6   15/36   21/36   0.42    6       5

   2-5   19/36   17/36   0.53    7       3

   3-5   14/36   22/36   0.39    8       2
   2-6   13/36   23/36   0.36    8       4
   4-4   11/36   25/36   0.31    8       0

   3-6   10/36   26/36   0.28    9       3
   4-5   10/36   26/36   0.28    9       1

   4-6    8/36   28/36   0.22   10       2
   5-5    6/36   30/36   0.17   10       0

   5-6    6/36   30/36   0.17   11       1
   6-6    4/36   32/36   0.11   12       0

It looks to me like the rule of 2.5 works just fine.

--
don
« Last Edit: February 13, 2008, 08:31:57 PM by don »
So many string dimensions, so little space time...

Offline Hardy_whv

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Re: Move 104 - 2 checker bear off
« Reply #5 on: February 15, 2008, 06:34:25 AM »
Yes, I got to know this principle from Thomas Koch's Backgammon Blog.

And for all who understand German, that's the link to the 2.5 article: http://graswurzelbackgammon.wordpress.com/2007/12/10/ungefahr-genau-25/

Hardy  B)
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Offline don

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Re: Move 104 - 2 checker bear off
« Reply #6 on: February 15, 2008, 08:42:10 PM »
For those (like me) who don't read German, Google/translate does a frequently amusing but useful job on Koch's excellent graswurzel (grass roots?) site:
http://translate.google.com/translate?u=http%3A%2F%2Fgraswurzelbackgammon.wordpress.com%2F&langpair=de%7Cen&hl=en&ie=UTF-8
Yes, I got to know this principle from Thomas Koch's Backgammon Blog.

And for all who understand German, that's the link to the 2.5 article: http://graswurzelbackgammon.wordpress.com/2007/12/10/ungefahr-genau-25/

Hardy  B)
The apple is to meet such a thing (Den Apfel zu treffen ist so eine Sache.)!!!  You will find a discussion of the rule of 2.5 on the bottom of the page which extends this conversation nicely.

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don
« Last Edit: February 15, 2008, 08:55:24 PM by don »
So many string dimensions, so little space time...

Offline wintom

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Re: Move 104 - 2 checker bear off
« Reply #7 on: February 15, 2008, 11:34:38 PM »
Thanks for the promotion Hardy :blush: and thanks Don for waking me up and pointing out this discussion! :blush: In fact Don already posted the rec.games.backgammon link where Neil Kazaross explains the 2 or 3 rule wich I converted into the 2.5 rule. Positions like this don't come up too often and the equity loss is not too big, but why sacrifice peanuts when you are hungry? Life rarely is as simple as remembering 2.5... ;)

Thomas
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Re: Move 104 - 2 checker bear off
« Reply #7 on: February 15, 2008, 11:34:38 PM »

Offline spielberg

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Re: Move 104 - 2 checker bear off
« Reply #8 on: February 16, 2008, 10:08:29 AM »
I apologise for my error and will now be using 2.5. Amusingly don initially agreed with me and has now edited his error out.

PS I should have known - Hardy's very, very good and his site http://www.hardys-backgammon-pages.com/ an excellent resource.

Offline don

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Re: Move 104 - 2 checker bear off
« Reply #9 on: February 16, 2008, 09:50:34 PM »
Ya caught me in the act, spielberg!
Amusingly don initially agreed with me and has now edited his error out.
Guilty as charged.

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don
So many string dimensions, so little space time...

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