Double When Facing Gammon
Andrew Bokelman
to run around and avoid a gammon, so I doubled. My reasoning was that if I
hit and won, I could win more points. But if I didn't hit, I lost nothing
extra by doubling.
Snowie disagrees with my double. And maybe I should have looked at the
possibility of hitting and avoiding a gammon instead of hitting and
winning. What do you think of doubling in the below position?
--------------------------------------------------------------------
| AndrewB (X) vs. opponent (O) |
| 7 point Match |
--------------------------------------------------------------------
Match to 7. Score X-O: 3-5
-------------------------- Move 17 X -------------------------
X on roll, cube action
+24-23-22-21-20-19-------18-17-16-15-14-13-+
| X O O O | | X X |
| X O O O | | X |
| O O | | X | S
| O O | | | n
| O | | | o
| |BAR| | w
| | | | i
| | | | e
| X | | |
| X X | | X |
| X X X | | X X |
+-1--2--3--4--5--6--------7--8--9-10-11-12-+
Pipcount X: 160 O: 31 X-O: 3-5/7 (8)
Men Off X: 0 O: 4
CubeValue: 1
3-Ply Money equity: -1.576
0.0% 0.0% 11.3% 88.7% 75.2% 5.0%
Double decision Good enough: 0% (0.00/0.29)
Too good to double: 0%
Take decision Current Doubled Borderline
Equities: -2.027 -0.774 0.584
Proper cube action: No double, take
JP White
> I was in a 7 pt match trailing 3 to 5. It looked to me like there was no way
> to run around and avoid a gammon, so I doubled. My reasoning was that if I
> hit and won, I could win more points. But if I didn't hit, I lost nothing
> extra by doubling.
The chances of you winning are very remote.
However it may be possible for you to avoid the gammon if you hit. This way you
may be able to stay in the match a while longer. Not likely, but just maybe.
Hope for a hit to stay in the match, but don't risk the match on a very long
shot.
--
JP White
Mailto:jp.w...@nashville.com
Julian Hayward
Bokelman <73457...@CompuServe.COM> writes
>I was in a 7 pt match trailing 3 to 5. It looked to me like there was no way
>to run around and avoid a gammon, so I doubled. My reasoning was that if I
>hit and won, I could win more points. But if I didn't hit, I lost nothing
>extra by doubling.
Snowie has probably spotted the case you failed to include above: when
you hit, manage to contain the opponent long enough to get within
gammon-saving distance, but then he escapes and you lose. When this
happens you'll regret doubling...
--
Julian Hayward 'Booles' on FIBS jul...@ratbag.demon.co.uk
+44-1344-640656 http://www.ratbag.demon.co.uk/
---------------------------------------------------------------------------
"Doh! Stupid poetic justice!" - Homer Simpson
---------------------------------------------------------------------------
Andrew Bokelman
>The chances of you winning are very remote.
>However it may be possible for you to avoid the gammon if you hit. This way
>you may be able to stay in the match a while longer. Not likely, but just
>maybe.
IOW, if I hit one checker I may delay my opponent long enough to come
around. And even though I loose, the match is not over. But if I double and
don't win (by hitting another checker or the dice going my way), then I loose
the match.
Kit Woolsey
: I was in a 7 pt match trailing 3 to 5. It looked to me like there was no way
: to run around and avoid a gammon, so I doubled. My reasoning was that if I
: hit and won, I could win more points. But if I didn't hit, I lost nothing
: extra by doubling.
: Snowie disagrees with my double. And maybe I should have looked at the
: possibility of hitting and avoiding a gammon instead of hitting and
: winning. What do you think of doubling in the below position?
: --------------------------------------------------------------------
: | AndrewB (X) vs. opponent (O) |
: | 7 point Match |
: --------------------------------------------------------------------
: Match to 7. Score X-O: 3-5
: -------------------------- Move 17 X -------------------------
: X on roll, cube action
: +24-23-22-21-20-19-------18-17-16-15-14-13-+
: | X O O O | | X X |
: | X O O O | | X |
: | O O | | X | S
: | O O | | | n
: | O | | | o
: | |BAR| | w
: | | | | i
: | | | | e
: | X | | |
: | X X | | X |
: | X X X | | X X |
: +-1--2--3--4--5--6--------7--8--9-10-11-12-+
: Pipcount X: 160 O: 31 X-O: 3-5/7 (8)
: Men Off X: 0 O: 4
: CubeValue: 1
Your error is a very common one; I have seen experts make it several
times. Clearly there is a small downside to doubling. You might hit a
late shot when your opponent has borne almost all of his men off. If
this happens you can save the gammon by building a prime and walking it
home, but you are still an underdog to win the game. If this happens you
will be behind 4 away, 0 away -- no bargain, but it is better than losing
the match outright.
Is there an upside to doubling? Your thinking that most of your losses
will be gammons is quite correct, so it would appear that there is more
to gain than to lose by doubling. In fact, if your only options were to
double now or never double, then doubling now would probably be the
percentage move.
However, this is not your last chance to double. If you wait, you will
have that option every time it is your turn to roll. So, let's suppose
you wait, roll something, and your opponent rolls 4-3 and has to leave
you a shot. Now let's suppose you double. Will he take? Of course he will.
Therefore, in your most favorable scenario for the next exchange (i.e.
you roll, he rolls), he will still have a take. Consequently there is no
upside for doubling now. To put it another way, it is impossible for you
to lose your market on the next exchange, since your opponent will always
have a take next turn no matter what happens. Therefore doubling now is
incorrect.
If you get the shot next turn, it might be correct to double. If your
opponent would have a pass after you hit the shot, then doubling would
probably be correct. However if your opponent would still have a take
after you hit the shot, then doubling would be wrong for the same reason
-- you couldn't lose your market.
This is a very difficult concept to understand, and players often make
desparation doubles of this sort when uncalled for. The main principle
is very simple: If it is impossible for you to lose your market on the
next exchange, then it is never correct to double.
Kit
Andrew Bokelman
>If you get the shot next turn, it might be correct to double. If your
>opponent would have a pass after you hit the shot, then doubling would
>probably be correct. However if your opponent would still have a take
>after you hit the shot, then doubling would be wrong for the same reason
>-- you couldn't lose your market.
Thanks. This is give me more detail and I'll keep it in mind.