From: martys@juliet.ll.mit.edu ( Marty Storer )
Subject: Re: When is 8/5,6/5 wrong?
Organization: M.I.T. Lincoln Lab - Group 43
	<1992Apr14.185635.1759@nic.csu.net>
	<MARTYS.92Apr15092420@escalus.juliet.ll.mit.edu>
	<1992Apr15.150445.217331@cs.cmu.edu>
Date: 15 Apr 92 13:54:39

In article <1992Apr15.150445.217331@cs.cmu.edu> jab+@cs.cmu.edu (Justin Boyan) writes:

>   If your opponent opens the game with any of the following plays, and
>   then you roll a 3-1, for which of them (if any) would you pass up the
>   chance to make your 5-point in order to hit?
>
>   Opponent's roll & play
>
>   6-3 :  1-10
>   6-3 :  1-7, 12-15
>   6-2 :  12-20
>   6-2 :  1-7, 12-14
>   5-1 :  1-7
>   5-1 :  12-17, 19-20
>   2-1 :  12-14, 19-20
>
>   I'm inclined to hit when the opponent slots on 20, but I'm unsure when
>   she runs one of her back checkers ...


  I'm pretty confident about all the following plays I make with 31 (I've
  changed notation to reflect common usage these days:  opponent's 1 point
  is your 24 point, etc.--i.e. each point has two names, as in English
  Descriptive chess notation):

	63: 24/15; 31 13/10*, 24/23.
	63: 24/18, 13/10; 31: 8/5, 6/5.
	62: 13/5; 31: 24/20*.
	62: 24/18, 13/11; 31: 8/5, 6/5.
	51: 24/18; 31: 8/5, 6/5.
	51: 13/8, 6/5; 31: 24/20*.
	21: 13/11, 6/5; 31: 24/20*.

  After opponent splits to your bar point, it's somewhat close between
  making your 5 point and either hitting and splitting or hitting and
  playing 13/10; but I still prefer the 5 point.  If opponent hits back,
  she's gained significantly; if not, she's still not too badly off.
  Drawback of making 5 point is that you leave her alone to make points;
  but in return you have the 5 point.  If she makes a blocking point on
  her side, you can attack on your bar point with a threat to make a
  four-point prime.

  (A related question is how to play 42 after opponent splits to your
  bar point:  in that case I'm really not sure what's right.  Long ago,
  Paul Magriel said the best play was to hit, but that's just an opinion
  anyway.  For what it's worth, the cognoscenti now seem to be choosing the
  hit.  Hitting neither creates a new builder nor splits, as does hitting
  with 31, but it doesn't strip the 8 point; and the 4 point as an alternative
  is less valuable than the 5 point.  Think, analyze, keep track of results,
  and take your pick...)

  After opponent slots her 5 point, you really have to hit:  you gain
  ground in the race and threaten to make the 20 point.  If you make your
  5 point, the game is pretty even since opponent will probably just make
  hers.

  After opponent runs with 63, it's very clearly right to hit.  You gain 10
  pips of race, prevent immediate escape of a back womyn, gain all the benefits
  of adding a builder and splitting, and gain a tempo.  If you make your 5
  point, your opponent probably just gets the 15-point checker around and
  adds a builder; you have a better board and are on roll, but opponent has
  one back vs. two.  Maybe a very slight edge to you since you're on roll,
  but nowhere near the edge you have after hitting.

  Notice I treat all plays that slot the 5 point the same; also all plays
  that split to our bar.  It could be that some of the slight differences
  in the splitting plays favor hitting over making the 5 point, but I don't
  think so...


			Play well,

			Marty

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