Trap play questions
Philippe Michel
+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 ?
If X tries to close the 2 back men out, should he break the 8 point only
or the 7 and 8 ?
Should X have tried to roll his prime one step forward before hitting the
second man ? Should he have tried to close his board ?
tpt...@goldengate.net
> +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 ?
I'd double. Slim chances of a gammon.
>
>If X tries to close the 2 back men out, should he break the 8 point only
>or the 7 and 8 ?
I'd Break the 8 only. if he has no rolled a 6 by the time you get the
rest home then you've probably won the race. Plus you'll have the blot
on the 2 to hit. if you open 7&8 you triple the chances of him
ecsaping (6-6, 6-5, 5-6)
>
>Should X have tried to roll his prime one step forward before hitting the
>second man ?
Nope
>Should he have tried to close his board ?
not unless it's convieniant. Just keep the scond man trapped. Leave a
blot if you have to The chances of a 6-2 are slim. if he does get a
6-2 i'd be nice to have some additial men back in addition to the one
he sent back.
Kit Woolsey
Philippe Michel (mic...@thomson-lcr.fr) 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 ?
If X doubles, O's takepoint is 15%. I don't think O will win that often
(although it might be closer than one might think), so O should pass.
Should X play on? Not clear. X's gammon chances aren't great, but they
do exist. The downside isn't very great. The only way X could really
get into trouble fast is if he goes for the squeeze and O rolls the
killing doubles immediately. I think I would take a roll, and then if I
didn't immediately get a successful squeeze going I would cash.
: If X tries to close the 2 back men out, should he break the 8 point only
: or the 7 and 8 ?
Neither! The best squeeze technique here is to break the 7 point and
hold the 8 point. This gains big if O rolls 5-1, and limits how far O
can escape if O is forced to run with one checker.
: Should X have tried to roll his prime one step forward before hitting the
: second man ? Should he have tried to close his board ?
I would have to see the exact position in order to answer this question.
In general, however, hitting the second checker is likely to be correct.
Kit
Brian Sheppard
Philippe Michel <mic...@thomson-lcr.fr> wrote in article
<E5yAq...@news.thomson-lcr.fr>...
> +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.
Brian
tpt...@goldengate.net
On Fri, 21 Feb 1997 23:55:58 GMT, kwoo...@netcom.com (Kit Woolsey)
wrote:
>Philippe Michel (mic...@thomson-lcr.fr) 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
>
>: If X tries to close the 2 back men out, should he break the 8 point only
>: or the 7 and 8 ?
>
>Neither! The best squeeze technique here is to break the 7 point and
>hold the 8 point. This gains big if O rolls 5-1, and limits how far O
>can escape if O is forced to run with one checker.
Kit
I think the trap (forcing him to leave one man back and hit it) in
this case is a much beter plan then the squeze. It of course, depends
on the rolls. If he can force hin to break that point he han hopefully
close the table and have a chance (although unlikly) at the gammon.
The trap is what he is asking about.
This is if O's is foolish enough to take the double....
tom
Tom Keith
Kit Woolsey wrote:
>
> Philippe Michel (mic...@thomson-lcr.fr) 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
>
>
> If X doubles, O's takepoint is 15%. I don't think O will win that often
> (although it might be closer than one might think), so O should pass.
>
> Should X play on? Not clear. X's gammon chances aren't great, but they
> do exist. The downside isn't very great. The only way X could really
> get into trouble fast is if he goes for the squeeze and O rolls the
> killing doubles immediately. I think I would take a roll, and then if I
> didn't immediately get a successful squeeze going I would cash.
Trap play?
Squeeze?
I'd like to add these terms to my backgammon glossary at
"http://www.bkgm.com/glossary.html".
Can somebody provide good definitions?
Tom
Ken Arnold, President of CyberArts
mic...@thomson-lcr.fr (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 ?
>If X tries to close the 2 back men out, should he break the 8 point only
>or the 7 and 8 ?
>Should X have tried to roll his prime one step forward before hitting the
>second man ? Should he have tried to close his board ?
It is actually very powerful to break the 4 point or the 5 point! If
O rolls the relevant double, you are still in control, whereas leaving
him 5's or boxes risks a fast turnaround. I propped this position
against two world-class players and both agreed after a few hours.
Lasse Hjorth Madsen
In article <5erap1$m...@camel2.mindspring.com>,
Is that so? That sounds really interesting. Just to get a well-defined
problem: if X rolls in the above diagram rolls, say, 31 should he actually
play the creative 4/3 4/1 ? Or should he leave the 4 point slotted? Could
you explain please?
Lasse
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Brian Sheppard
Tom Keith <t...@bkgm.com> wrote in article <330FD1...@bkgm.com>...
> I'd like to add these terms to my backgammon glossary at
> squeeze
The equivalent of exploiting zugzwang in chess: to take advantage
of the opponent's compulsion to move any playable roll.
> trap play.
A trap play is a deliberate attempt to squeeze an opponent off of
his anchor, so that the trapper can close out any blots thereby
exposed and win a gammon.
Brian
Brian Sheppard
Kit Woolsey <kwoo...@netcom.com> wrote in article
<kwoolseyE...@netcom.com>...
> Philippe Michel (mic...@thomson-lcr.fr) wrote:
> : +24-23-22-21-20-19-+---+18-17-16-15-14-13-+
> : | 8 O | | X X |
> : | O O | | |
> : | O O | | |
> : | O O | | |
> : | O O | | |
> : | | | |
> : | O X X X X | | X X | 2
> : | O X X X X | | X X X |
> : +-1--2--3--4--5--6-+---+-7--8--9-10-11-12-+
> : Score: O 5 away, X 3 away ; X on roll
>
only
> : or the 7 and 8 ?
>
> hold the 8 point. This gains big if O rolls 5-1, and limits how far O
> can escape if O is forced to run with one checker.
At first I had the same thought, but my rollouts played a lot easier
when I broke both points. The important factor seemed to be that X did
not have time to wait for O to get a 5. O sometimes doesn't even roll a
5 or 6.
Brian
Ken Arnold, President of CyberArts
Answer: I believe so..... 4/3, 4/2 with 2-1 worked very well for me
in a proposition played against two top pros (Jason and Svobo). Both
were amazed and quit the prop.
ag.er...@aaa.dk (Lasse Hjorth Madsen) wrote:
>In article <5erap1$m...@camel2.mindspring.com>,
> kena...@spacelab.net wrote:
>>
>> mic...@thomson-lcr.fr (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 ?
>>
>> >If X tries to close the 2 back men out, should he break the 8 point only
>> >or the 7 and 8 ?
>>