Vision laughs at counting

Tim Chow

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Oct 26, 2011, 9:56:51 AM10/26/11

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Danny Kleinman wrote a big book entitled, "Vision Laughs at Counting:
With Advice to the Dicelorn." Given that it's from the pre-bot era,
it stands up pretty well, but of course, modern bots beg to differ
with Kleinman's assessments of some of the positions in the book.
Below is one example. What's your play?

XGID=aBBBCBB----------------bc-:1:1:1:32:0:0:3:0:10

X:Player 2 O:Player 1
Score is X:0 O:0. Money session
+24-23-22-21-20-19------18-17-16-15-14-13-+
| O O | | |
| O O | | |
| O | | |
| | | |
| | | |
| |BAR| |
| | O | |
| | | |
| X | | | +---+
| X X X X X X | | | | 2 |
| X X X X X X | | | +---+
+-1--2--3--4--5--6-------7--8--9-10-11-12-+
Pipcount X: 46 O: 32 X-O: 0-0
Cube : 2, X own cube
X to play 32

---
Tim Chow

Bradley K. Sherman

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Oct 26, 2011, 10:08:49 AM10/26/11

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Tim Chow <tchow...@yahoo.com> wrote:
>Score is X:0 O:0. Money session
> +24-23-22-21-20-19------18-17-16-15-14-13-+
> | O O | | |
> | O O | | |
> | O | | |
> | | | |
> | | | |
> | |BAR| |
> | | O | |
> | | | |
> | X | | | +---+
> | X X X X X X | | | | 2 |
> | X X X X X X | | | +---+
> +-1--2--3--4--5--6-------7--8--9-10-11-12-+

>Pipcount X: 46 O: 32 X to play 32

4/1,2/off

My thinking in these situations is that if O
comes in immediately, I lose, so leaving a blot
is not consequential. Which blot to leave is
not obvious to me. But is my move really
better than 3/2,3/off? Looking forward to
the rollout.

--bks

Paul

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Oct 26, 2011, 10:19:12 AM10/26/11

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I'll support Bradley's play. I think X's position would be greatly
improved if O exposed a blot on the 23 point.
This is quite likely with Bradley play. Of course, X would also
welcome a dance by O so I like the plays which only open up 1 point.

Paul Epstein

Walt

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Oct 26, 2011, 10:59:52 AM10/26/11

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The automatic bearoff play is to clear from the rear. But by clearing
the six point, if O shakes a 6 it's basically game over.

I'll play 2/0ff 4/1 - this means that entering rolls recirculate a
checker to maintain contact and 7 entering rolls 21 22 23 and 24 keep O
stuck.

Maybe 3/off 2/off is correct (it works well when it works), but my blood
is too thin for that at this time.

I thought about 3/off 3/2, but I think we need to force contact if O enters.

//Walt
//Walt

Stick

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Oct 26, 2011, 2:00:42 PM10/26/11

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Often in these situations when your opponent has so many men off you
have a couple of goals, bearing checkers off and keeping the strongest
board you possibly can for the longest amount of time that you can.
This means ripping checkers off from high points as you'll be able to
keep the board longer that way. It keeps your position smoother for
bearing off too.

Nobody has mentioned it yet so with all that in mind, what think ye of
5/off?

Stick
http://www.bgonline.org/forums/

Michael Plog

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Oct 26, 2011, 4:46:24 PM10/26/11

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This is a money game, score 0-0. Why not take off two checkers and
try for as much contact as possible until you catch up? If O comes in
then have a checker back in order to hit again.

Paul

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Oct 27, 2011, 5:28:45 AM10/27/11

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I don't like your play, Stick, because I'm a massive fan of the tactic
of trying to get O to expose another blot and then trying to hit it.
Admittedly, it didn't work last time I advocated it, but I'm not going
to give up on it yet. Your suggestion isn't very good for my tactic.
I doubt that gnubg is good at recognizing this tactic because it
reguires a huge-ply lookahead to spot, 3-ply is not enough.

It thinketh me that 5-off would not bring joy to the climes of
Denmark.

Paul Epstein

badgolferman

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Oct 27, 2011, 10:53:13 AM10/27/11

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4/1, 2/off.

Yes, I want to keep O back as long as I can and eventually get at least
one of my checkers back to O's home board. My intent is to open up the
low points on my board and hope O gets in. Hopefully O won't escape
before it rolls a 1 and has to leave a blot on its 2-point for me to
smash.

Tim Chow

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Oct 27, 2011, 3:17:43 PM10/27/11

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On Oct 26, 9:56 am, I wrote:
> XGID=aBBBCBB----------------bc-:1:1:1:32:0:0:3:0:10
>
> X:Player 2 O:Player 1
> Score is X:0 O:0. Money session
> +24-23-22-21-20-19------18-17-16-15-14-13-+
> | O O | | |
> | O O | | |
> | O | | |
> | | | |
> | | | |
> | |BAR| |
> | | O | |
> | | | |
> | X | | | +---+
> | X X X X X X | | | | 2 |
> | X X X X X X | | | +---+
> +-1--2--3--4--5--6-------7--8--9-10-11-12-+
> Pipcount X: 46 O: 32 X-O: 0-0
> Cube : 2, X own cube
> X to play 32

This sort of position is deceptively simple-looking, but there are a
lot of things to consider.

Let's start by arguing that 3/off 2/off can't be better than 4/1 2/
off. Suppose we play 2/off and have to decide between 3/off and 4/1.
If O rolls 63 53 43 33, would you prefer that O dance or would you
prefer that O hit you? It should be clear that we would prefer O to
dance. Getting hit accomplishes nothing other than making us an
underdog to hit O as she comes around the board; the best-case
scenario is to put O back on the bar again, where she would be anyway
if she danced. Of course O's 31 from the bar plays better for us
after 3/off, but this is canceled out by the fact that O's 21 from the
bar plays better for us after 4/1. A play like 3/off 2/off is usually
correct only if O *already* has a blot in her home board that we're
trying to pick up. The only real advantage of 3/off 2/off is that it
takes off another checker, but since we're so far behind in the race
anyway, one extra checker off can't compensate for the extra lost
point. When we're behind like this, it's rarely correct to reduce to
a four-point board voluntarily when we can keep a five-point board.

Now for the more subtle question. Given that we are going to break a
point, which point should we break? Breaking a high point has the
following advantages: It typically uses pips more efficiently for the
race, and it typically allows us to keep a strong board a little
longer. Breaking a low point has the following advantages: If O
enters then we have a better chance of sending her back to the bar
with a hit, or, failing that, of blocking some of her rolls, perhaps
forcing O to play 2/1 with an ace. Also, keeping the high points
closed blocks some of our opponent's best racing rolls.

Generally, the rule of thumb is that if we are underdogs, then we
should play to use pips efficiently and keep our board longer, not
worrying so much about what to do if O enters since we're probably
going to be hosed anyway in that case. That means breaking a high
point and not worrying about leaving a blot on the broken point if we
can use the pips efficiently otherwise. On the other hand, if we're
slight favorites, then usually we should open up a lower point,
increasing our counterchances if O does enter. Finally, of course, if
we're big favorites (but gammons don't count or are very unlikely),
then we should just clear from the rear and avoid getting hit.

In the position I posted, Kleinman advocated 3/1 3/off, but the
rollout indicates that we're far enough behind that 5/off is better.
If we give O an extra checker, then it's pretty much a toss-up. If we
give O yet another checker, then 3/1 3/off comes out on top.

=======
Rollout
=======

1. Rollout: 5/0ff eq:-0.079
Player : 38.55% (G:0.00% B:0.00%)
Opponent: 61.45% (G:0.00% B:0.00%)
Confidence: ±0.006 (-0.085<E<-0.073)

2. Rollout: 4/1 2/0ff eq:-0.123 (-0.044)
Player : 36.77% (G:0.00% B:0.00%)
Opponent: 63.23% (G:0.00% B:0.00%)
Confidence: ±0.008 (-0.131<E<-0.115)

3. Rollout: 3/1 3/0ff eq:-0.136 (-0.057)
Player : 36.83% (G:0.00% B:0.00%)
Opponent: 63.17% (G:0.00% B:0.00%)
Confidence: ±0.006 (-0.142<E<-0.130)

4. Rollout: 4/2 3/0ff eq:-0.168 (-0.089)
Player : 35.05% (G:0.00% B:0.00%)
Opponent: 64.95% (G:0.00% B:0.00%)
Confidence: ±0.007 (-0.175<E<-0.161)

5. Rollout: 6/4 6/3 eq:-0.184 (-0.105)
Player : 34.37% (G:0.00% B:0.00%)
Opponent: 65.63% (G:0.00% B:0.00%)
Confidence: ±0.005 (-0.189<E<-0.179)

1296 Games rolled with Variance Reduction.
Dice Seed: 2
Moves and cube decisions: 3 ply

eXtreme Gammon Version: 1.21

=========
Variant 1
=========

XGID=aBBBCBB----------------cc-:1:1:1:32:0:0:3:0:10

X:Player 2 O:Player 1
Score is X:0 O:0. Money session
+24-23-22-21-20-19------18-17-16-15-14-13-+
| O O | | |
| O O | | |
| O O | | |
| | | |
| | | |
| |BAR| |
| | O | |
| | | |
| X | | | +---+
| X X X X X X | | | | 2 |
| X X X X X X | | | +---+
+-1--2--3--4--5--6-------7--8--9-10-11-12-+

Pipcount X: 46 O: 34 X-O: 0-0

Cube : 2, X own cube
X to play 32

1. Rollout: 5/0ff eq:+0.069
Player : 44.80% (G:0.00% B:0.00%)
Opponent: 55.20% (G:0.00% B:0.00%)
Confidence: ±0.003 (+0.066<E<+0.072)

2. Rollout: 3/1 3/0ff eq:+0.064 (-0.005)
Player : 45.43% (G:0.00% B:0.00%)
Opponent: 54.57% (G:0.00% B:0.00%)
Confidence: ±0.003 (+0.061<E<+0.067)

3. Rollout: 6/4 6/3 eq:+0.034 (-0.035)
Player : 43.66% (G:0.00% B:0.00%)
Opponent: 56.34% (G:0.00% B:0.00%)
Confidence: ±0.007 (+0.027<E<+0.041)

4. Rollout: 4/1 2/0ff eq:+0.006 (-0.063)
Player : 42.23% (G:0.00% B:0.00%)
Opponent: 57.77% (G:0.00% B:0.00%)
Confidence: ±0.007 (-0.001<E<+0.013)

Candidates 1 and 2: 5184 Games rolled with Variance Reduction.
Candidates 3 and 4: 1296 Games rolled with Variance Reduction.
Dice Seed: 2
Moves and cube decisions: 3 ply

=========
Variant 2
=========

XGID=aBBBCBB----------------cd-:1:1:1:32:0:0:3:0:10

X:Player 2 O:Player 1
Score is X:0 O:0. Money session
+24-23-22-21-20-19------18-17-16-15-14-13-+
| O O | | |
| O O | | |
| O O | | |
| O | | |
| | | |
| |BAR| |
| | O | |
| | | |
| X | | | +---+
| X X X X X X | | | | 2 |
| X X X X X X | | | +---+
+-1--2--3--4--5--6-------7--8--9-10-11-12-+

Pipcount X: 46 O: 35 X-O: 0-0

Cube : 2, X own cube
X to play 32

1. Rollout: 3/1 3/0ff eq:+0.352
Player : 57.19% (G:0.00% B:0.00%)
Opponent: 42.81% (G:0.00% B:0.00%)
Confidence: ±0.007 (+0.345<E<+0.359)

2. Rollout: 6/4 6/3 eq:+0.319 (-0.034)
Player : 55.19% (G:0.00% B:0.00%)
Opponent: 44.81% (G:0.00% B:0.00%)
Confidence: ±0.005 (+0.314<E<+0.324)

3. Rollout: 5/0ff eq:+0.275 (-0.078)
Player : 53.01% (G:0.00% B:0.00%)
Opponent: 46.99% (G:0.00% B:0.00%)
Confidence: ±0.005 (+0.270<E<+0.280)

4. Rollout: 4/1 2/0ff eq:+0.231 (-0.121)
Player : 51.12% (G:0.00% B:0.00%)
Opponent: 48.88% (G:0.00% B:0.00%)
Confidence: ±0.007 (+0.224<E<+0.238)

1296 Games rolled with Variance Reduction.
Dice Seed: 2
Moves and cube decisions: 3 ply

---
Tim Chow

Tim Chow

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Oct 27, 2011, 4:45:51 PM10/27/11

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There was one other thing I forgot to say. Comparing 3/1 3/off with
4/1 2/off, I think the reason 3/1 3/off is better (at least when 3/1 3/
off is the top play) is that it leaves us with a spare on the 4pt to
hit O's checker if O enters.

---
Tim Chow

markx

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Oct 28, 2011, 9:52:08 AM10/28/11

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On 27 Okt., 11:28, Paul <pepste...@gmail.com> wrote:
> I don't like your play, Stick, because I'm a massive fan of the tactic
> of trying to get O to expose another blot and then trying to hit it.

After 5/off X gets a shot if 0 enters with 51.
After 2/off X gets a shot if 0 enters with 21.
No difference now, and on the next roll X has to open something more
anyway.