Strategy--Checker play

Forum Archive : Strategy--Checker play

Trap play problem

From:   Brian Sheppard
Date:   21 February 1997
Subject:   Re: Trap play questions
Google:   01bc200a$8c70dd60$

Philippe Michel wrote:
>    +24-23-22-21-20-19-+---+18-17-16-15-14-13-+
>    | 8  O             |   |          X  X    |
>    | O  O             |   |                  |
>    | O  O             |   |                  |
>    | O  O             |   |                  |
>    | O  O             |   |                  |
>    |                  |   |                  |
>    |    O  X  X  X  X |   | X  X             | 2
>    |    O  X  X  X  X |   | X  X     X       |
>    +-1--2--3--4--5--6-+---+-7--8--9-10-11-12-+
>    Score: O 5 away, X 3 away ; X on roll
>    What is the correct cube action ?

Why not roll? After all, nothing dramatic will happen next turn.

I did an interactive rollout against JF Level 7, since JF Level 6
badly mishandles X's position. X wins 84.6%, with 24.9% gammons
against O's 15.4% wins and negligible gammons. X's cubeless equity
is 0.935, with a standard deviation of 0.028. It is hard to be
certain that X's equity when owning the cube exceed 1.000, but my
gut feel is that it does, since it seemed to me that about half
of X's losses occurred after X would have doubled O out of the game.

The tactics that X should pursue are as follows:

    0) Keep the 2 men back on the 14 ad 15 points unless forced
    to move off. (JF Level 6 moves these men.) If you are forced
    to move one of those men, prefer to move the 15 point, since
    keeping the 14 point man allows you to win if O rolls 6-6.

    1) Break the 7 or 8 points at the first opportunity. Give
    preference to breaking the 8-point first, since it is easier
    to break the 7 later.

    2) Break the other point at the first opportunity. JF Level 6
    will keep both outside points.

    3) Use the blot on the 10 point as spare timing in case you have a
    roll that doesn't break the outside priming points. Note that if
    the opponent had a board threat then you would not be able to
    use this resource, since an outfield hit could be fatal.

    4) Hit all blots. Given the choice between closing out with one
    man on the bar and having a 5-point board with 2 men, you should
    choose to hit 2 men, even if it means leaving a blot. Again, the
    opponent's crunched board makes this tactic possible.

    5) Do not be afraid to slot the ace point, or cover it, if
    that will allow you to keep the hitting checkers in place. After
    all, you intend to cover that point anyway!

    6) Double O out if you are forced to move the back checkers.
    By that point there is little hope of winning a gammon.

X's ownership of the cube is very important, as is O's weak board.
Without those two factors the tactics outlined above would not work.

For this tournament situation you should cash, possibly after letting
a roll or two go by, just to see how things develop. If any awkwardness
appears, however, you should cash. If the score were reversed, then playing
on would be clear.

> Should X have tried to roll his prime one step forward before hitting the
> second man ?  Should he have tried to close his board ?

In containment situations you should hit just about every blot.

Did you find the information in this article useful?          

Do you have any comments you'd like to add?     


Strategy--Checker play

Avoiding major oversights  (Chuck Bower+, Mar 2008) 
Bearing off with contact  (Walter Trice, Dec 1999) 
Bearing off with contact  (Daniel Murphy, Mar 1998)  [Long message]
Blitzing strategy  (Michael J. Zehr, July 1997) 
Blitzing strategy  (Fredrik Dahl, July 1997) 
Blitzing technique  (Albert Silver+, July 2003)  [GammOnLine forum]
Breaking anchor  (abc, Mar 2004) 
Breaking contact  (Alan Webb+, Oct 1999) 
Coming under the gun  (Kit Woolsey, July 1996) 
Common errors  (David Levy, Oct 2009) 
Containment positions  (Brian Sheppard, July 1998) 
Coup Classique  (Paul Epstein+, Dec 2006) 
Cube ownership considerations  (Kit Woolsey, Apr 1996) 
Cube-influenced checker play  (Rew Francis+, Apr 2003)  [GammOnLine forum]
Defending against a blitz  (Michael J. Zehr, Jan 1995) 
Estimating in volatile situations  (Kit Woolsey, Mar 1997) 
Gammonish positions  (Michael Manolios, Nov 1999) 
Golden point  (Henry Logan+, Nov 2002) 
Hitting loose in your home board  (Douglas Zare, June 2000) 
Holding games  (Casual_Observer, Jan 1999)  [Long message]
How to trap an anchor  (Timothy Chow+, Apr 2010) 
Jacoby rule consideration  (Ron Karr, Nov 1996) 
Kamikaze plays  (christian munk-christensen+, Nov 2010) 
Kleinman Count for bringing checkers home  (Øystein Johansen, Feb 2001) 
Late loose hits  (Douglas Zare+, Aug 2007)  [GammOnLine forum]
Mutual holding game  (Ron Karr, Dec 1996) 
Pay now or pay later?  (Stuart Katz, MD, Nov 1997) 
Pay now or pay later?  (Stephen Turner, Mar 1997) 
Pay now or play later?  (Hank Youngerman+, Sept 1998) 
Play versus a novice  (Courtney S Foster+, Apr 2004)  [GammOnLine forum]
Playing doublets  (Grunty, Jan 2008) 
Playing when opponent has one man back  (Kit Woolsey, May 1995) 
Prime versus prime  (Albert Silver+, Aug 2006)  [GammOnLine forum]
Prime versus prime  (Michael J. Zehr, Mar 1996) 
Saving gammon  (Bill Riles, Oct 2009) 
Saving gammon  (Ron Karr, Dec 1997) 
Splitting your back men  (KL Gerber+, Nov 2002) 
Splitting your back men  (David Montgomery, June 1995) 
Trap play problem  (Brian Sheppard, Feb 1997) 
When in doubt  (Stick+, Apr 2011) 
When to run the last checker  (Stick Rice+, Jan 2009) 
When you can't decide  (John O'Hagan, Oct 2009) 

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