Search This Blog

November 17, 2012

Late Game Containment - theory

These are mostly notes from Stick's excellent lecture on Late Game Containment.  He discusses checker play strategy and tactics, for situations where you hit a late shot in the bearoff.  I made a similar post on my old blog in reference to an online match against Mochy.  Unfortunately, I deleted the old blog and didn't save any old posts or notes from that exercise.

This is the stem position.  Idea is to play it yourself against the computer over and over, make blunders and learn.  Shown here to discuss some of the main strategical and tactical themes for late game containment.
is Player 2

score: 0
pip: 38
Unlimited Game
Jacoby Beaver
                          pip: 181
score: 0

is Player 1
on roll, cube action?

Analyzed in XG Roller+ No redouble Redouble/Take
  Player Winning Chances: 43.01% (G:0.00% B:0.00%) 42.88% (G:0.00% B:0.00%)
  Opponent Winning Chances: 56.99% (G:39.43% B:1.22%) 57.12% (G:39.50% B:1.19%)
  Cubeless Equities -0.546 -1.099
Cubeful Equities
No redouble:-0.395
Redouble/Beaver:-2.000 (-1.605)
Redouble/Pass:+1.000 (+1.395)
Best Cube action: No redouble / Beaver
Percentage of wrong pass needed to make the double decision right: 34.9%
eXtreme Gammon Version: 2.02

These are roughly in descending order of importance.

Structural / Static Themes

  • How many checkers has the opponent borne off?
    • This is very important because it impacts when you can recube.
      • Less than 5 off, you can often recube before the closeout is complete.
      • Even with 5 off, you may be able to recube depending on how bad the opponent's homeboard is
      • It may be right to leave a key point slotted, using the power of the recube to your advantage.  For example, opponent is on bar against 5 1/2 point board.  Leave the point slotted and recube if he dances.
    • Do you need a second checker?
      • 5 or 6 off (or less), usually don't need it.  Would be nice to get of course, but don't need to take reckless chances going for it.  Why?  Becuase you will be a large favorite anyway if you close one man out.
      • 7 off (or more), usually would like to get the second checker.  Same reasoning about risk and reward.  Now even after you close him out you may be only 50-50 or even an underdog.  Picking up a second checker has a lot of upside as you can recube him out if you get it, and sometimes just on the threat of picking up the second checker.
  • How strong is the opponent's home board.  This is huge since this determines how agressive / wimpy you need to be regarding loose hits.  Note the interplay of risk and reward.
    • 1 or 2 point board. Downside is low since if you get hit you are a large favorite to reenter immediately.  So you can play pure and hit loose to fight for the key points and prevent opponent from escaping. 
    • 3 point board. These are iffy, and depends on the specific position.  On one hand if you get hit you are still a favorite to reenter but on the other hand 25% of the time you dance.  You can easily go from sugar to shit in one sequence so you really need to consider the specific position.  Some questions:
      • How critical is it to hit? 
      • What is the downside? 
      • How does the roll play if you don't hit?
    • 4 point board or better.  Opponent's board deserves respect so tend towards safety.  That said, sometimes you gotta man up and hit anyway . Depends on the specific position.  Same questions as 3 point board apply but keep in mind the danger is greater.
      • How critical is it to hit?
      • What is the downside?
      • How does the roll play if you don't hit?
  • Match Score considerations.    At certain lopsided scores, the takepoints and gammon values  (for both sides) may be considerably different than money.  You could be more or less sensitive to gammons, and you could be recubing earlier or later depending on...
    • Gammon Value ATS
    • Takepoint ATS
Strategical Themes / Priorities

  • Flood the outfield with checkers to cover the escape zone.  Escape zone is where the opponent's checker lands when he partially escapes (typically 7-11 pips out).  You want to have plenty of ammunition aimed at this area so you have a double or triple shot to hit opponent's checker should he land there.
  • Build a winning prime / Close opponent out.  Obvious but let's keep the main goal in sight.
  • Blocking big doubles.
    • Low priority.
    • Generally a 'luxury' play, meaning only block the big doubles if you have the position under control already
      • How good is your outfield coverage?
    • If you can't improve your position much than blocking the big doubles could be right.
  • Avoid getting gammoned.
    • Generally a low priority and not what you should be thinking about.  You should be playing to win.  Keep in mind turning every single game you turnaround (-2 to + 2)compensates for two gammon losses (-2 to -4)  
    • But, if you can't win anyway (say he has 12 checkers off and you have a busted board) then you are really on gammon save.
    • Or if his board is too strong you may have to be extra cautious as the price of getting hit is too high.
Tactical / Checker Play Themes

  • Do you hit loose?  In addition to the strategical themes here are some tactical things to consider
    • How key is the point?
    • How does the roll play otherwise?
    • How strong is your outfield coverage?
    • How good is your blockade?
  • What are the important points to fill in?
    • Usually the 5 point, 4 point and the bar are the key points but it depends on the specific position.  So you are more likely to hit a checker loose that is sitting on one of these key points than a checker sitting on a deeper less valuable point such as 1, 2 or 3 point.
  • If opponent's board is blotted you can be more aggressive in hitting loose because of the return shots
  • You hit loose, opponent dances, and you don't cover.  Now what?
    • If you have a lot of covers already then you don't necessarily need to bring another builder down.  Doesn't add many covers but creates the joker sequence he enters and hits and you dance - a disaster.  (Don't automatically bring more covers down.  See what your other options are)
  • Generally don't move your furthest back checker as this is your last line of defence.
  • Banana split hit often right when opponent has a weak board with a blot.  Or if opponent has significant enter and crack numbers (to expose a blot).
  • Don't leave indirect shots if you don't have to.
  • Spreading checkers in the outfield -
    • outfield coverage tends to be better when checkers are adjacent to each other.
    • move off points (flood the outfield for maximum coverage of escape zone)
  • Dilly builders.  These guys have only one purpose - to fill in a low point.  Often right to hit loose or slot at earliest opportunity with these men.  This is especially true is opponent's board is weak and/or blotted. 

1 comment: