Thread View: rec.games.backgammon
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3 total messages
Started by Michael J Zehr
Thu, 15 Oct 1992 15:42
53 then 64 opening
Author: Michael J Zehr
Date: Thu, 15 Oct 1992 15:42
Date: Thu, 15 Oct 1992 15:42
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I received this by e-mail with a request to post:
24 23 22 21 20 19 | 18 17 16 15 14 13
X O O | O X
X O O | O X
O | X
O | X
| X
| X to play 6-4
X | O
X | O
X | X O
O X | X O
O X | X O
1 2 3 4 5 6 7 8 9 10 11 12
I agree with you. Making 2 is a bad move. The options are 24-18 13-9
and 24-14. Now everyone else (so far) has gone for 24-14 on the grounds
that a man on 14 is only exposed to a single shot, whereas on 18 it's a
double shot. But:
i) with 24-18, 13-9 there are far more possibilities for X next roll if
missed. 24-14 achieves very little, maybe nothing if the man on 14
can't be safetied next time. Even then the position is very inflexible.
ii) Being hit on 18 leaves far more return shots (6-1, 6-2, 6-4, 6-5,
5-2, 4-3) than on 14 (6-5).
iii) O is also unlikely to choose to hit you on 18 with most 1's.
Re: 53 then 64 opening
Author: Philip Stromer
Date: Thu, 15 Oct 1992 19:39
Date: Thu, 15 Oct 1992 19:39
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I think 24-18, 13-9 is a terrible move. I'd move 24-14. With 24-14, the blot is exposed to a direct 2 (11 hits). With 24-18, 13-9, the blot on 18 is exposed to 17 hits, plus the blot on 9 is exposed to 6 hits, for a total of 23 hits. The only duplicated rolls here are 6-2, 2-6, and 2-2. That's 20 *different* rolls, out of a possible 36, that hit the blot. There is no logical reason NOT to play 24-14. By moving 24-14, the blot on 14 is in excellent position to move to safety on the following roll if not hit. Also, X has now escaped one of his back men. --Philip Stromer-- E-mail: peewee@infoserv.com
Re: 53 then 64 opening
Author: Elliott C Winslow
Date: Fri, 16 Oct 1992 03:05
Date: Fri, 16 Oct 1992 03:05
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In article <s4aPsB2w163w@peewee> peewee@infoserv.com (Philip Stromer) writes: >There is no logical reason NOT to play 24-14. |24 23 22 21 20 19| |18 17 16 15 14 13| |X . O . . O | | . O . . . X| |X O O | | O X| | O | | X| | O | | X| | | | X| | [ ] | | X | | O| | X | | O| | X | | X O| |O X | | X O| |O . . . . X | | . X . . . O| |1 2 3 4 5 6 | | 7 8 9 10 11 12| X to play 6-4 There are a *lot* of good, logical reasons for playing 24-18, 13-9 over 24-14. They just require looking morely deeply than your one-roll hit-or-not-hit analysis. Just on the basis of who makes out better in exchanges of hits, the split/down play looks better. If I hit you back 1/3 of most of the times you hit me, then I'm almost equal right there. [One reason why this 6-4 is closer than 6-3 or 5-4 or 6-2, because with those the run leaves more shots.] But the "big swing" that makes the top players (well, some of them! :-) prefer the split/down plays, is that it is considered that there is *MORE* *TO* *GAIN* by splitting. If you end up with the bar-point, you've gained far more than most any other possibility; and an exchange of hits on the 18 also means that he is falling back in the race and the number of men back (two different, though obviously related, factors). When I first met Gerard Duguet-Grasser in Paris in 1987, he was very good but relatively inexperienced and "green" regarding some concepts. I showed him how it might be right to split with 4-3 after an opening 4-2: |24 23 22 21 20 19| |18 17 16 15 14 13| |X . . O X O | | . O . . . X| | O O | | O X| | O | | X| | O | | X| | | | | | [ ] | | X | | O| | X | | O| | X | | X O| |O X | | X O| |O . . . . X | | . X . X . O| |1 2 3 4 5 6 | | 7 8 9 10 11 12| You do this by applying partitioning, i.e. consider the likelihood of the different possibilities (O points, O misses and X covers, O misses and X doesn't cover, O hits loose and X hits, O hits loose and X misses, O hits 2, etc. etc. And then you do the same thing with the two-down play. It comes out tantalizingly close. Of course, it involves some extremely loose approximations, but that's the way it is. And I don't mean loose as in biased, I just mean how can you know. By the way, I think it was Roger Low who really sank in on this sort of principle, along with Paul Magriel of course; in any case I remember seeing Roger doing this play more than once in recorded matches. It could be a question of style and tournament situation as well, but as I started out saying in the summary: IT'S THE **CONCEPT** THAT YOU HAVE TO TRY TO GRASP. --Elliott
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