Game #2
Open Division Final
San Mateo, California
17 November 1996
11 Point Match
Kevin Mansfield (Black) vs. Nick Ballard (White)
Score: 0 - 0
Analysis by Steve Clark
This is the first game of the Open Division finals for November.
Kevin Mansfield,
known variously as lucky and as UNLUCKY in FIBSdom,
demonstrated his backgammon Skill
by playing through to the final round.
Nick Ballard,
known usually as Nack in all manner of gaming venues,
demonstrated his Nackedness.
We thank both participants for sharing this exciting sample game
from their match with us.
| Play 1a |
|
|
Black to play 52
Candidate Plays Equities
13/8 24/22 +0.005
13/8 13/11 +0.000
|
|
SC:
|
This rollout result surprised everyone when it first appeared.
Before rollouts,
13/8 24/22 was not considered a candidate move by any expert.
Now it is probably slightly preferred by players at all levels.
Which play you choose is really a matter of taste.
|
| |
Black
|
White
|
|
1.
|
52: 13/8 13/11
|
|
|
| Play 1b |
|
|
White to play 52
Candidate Plays Equities
13/8 13/11 -0.092
13/8 24/22 -0.111
13/8 6/4 -0.122
13/6 -0.163
8/3 13/11 -0.183
|
|
SC:
|
If your opponent rolls a 52 or 54 on the opening move,
it is generally best to imitate his method on play.
If he splits from the 24 point,
you should split from the 24 in reply.
If he brings builders from the 13 point,
you should bring builders from the 13 point in reply.
However, if he slots, do not slot in reply.
|
| |
Black
|
White
|
|
1.
|
...
|
52: 13/8 13/11
|
|
2.
|
31: 8/5 6/5
|
53: 8/3 6/3
|
|
3.
|
61: 13/7 8/7
|
41: 11/7 8/7
|
|
| Play 4a |
|
|
Black to play 53
Candidate Plays Equities
24/16 +0.229
8/3 6/3 +0.220
11/6 24/21 +0.192
13/8 13/10 +0.167
|
|
SC:
|
Normally playing 24/21 along with the 5 played elsewhere,
such as 13/8,
is to be preferred.
However,
here the 5 part of that play is awkward,
so other moves come to the forefront.
8/3 6/3 makes the 3 point,
which is valuable but leaves the back checkers hemmed in
and leaves a blot on the 8 point.
24/16 starts to escape but not particularly effectively.
The choice is close.
|
| |
Black
|
White
|
|
4.
|
53: 24/16
|
44: 13/9*/5(2)
|
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| Play 5a |
|
|
Black to play 11
Candidate Plays Equities
Bar/23 24/23 13/12* +0.326
Bar/24 13/12* 11/10 6/5 +0.278
Bar/24 13/12* 11/9 +0.229
Bar/24 13/12*/11 6/5 +0.224
Bar/24 13/12*(2) 6/5 +0.213
Bar/24 13/12*/10 +0.192
Bar/23 13/12* 6/5 +0.180
Bar/23 13/12*/11 +0.168
Bar/23 13/12*(2) +0.136
Bar/23 13/12* 11/10 +0.136
|
|
SC:
|
Bar/23 13/12 are clear with 3 parts of the move.
The choice is on the last ace,
with 24/23 being the clear winner.
This result might seem surprising,
but it has the benefit of denying White any hits with his awkward numbers.
Instead White often will have the break his 7 or 8 point soon,
without being able to attack.
If White were more likely to retain his partial prime,
then splitting would be much more desirable.
|
| |
Black
|
White
|
|
5.
|
11: Bar/23 13/12* 6/5
|
|
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| Play 5b |
|
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White to play 33
Candidate Plays Equities
Bar/22 24/21(2) 6/3 +0.155
Bar/22 24/21 7/4(2) +0.007
|
| |
Black
|
White
|
|
5.
|
...
|
33: Bar/22 24/21(2) 6/3
|
|
| Play 6a |
|
|
Black to play 11
Candidate Plays Equities
24/23 12/10 11/10 -0.044
24/23 13/11 12/11 -0.143
|
|
SC:
|
Again making the 23 point is the winner.
Putting blockers on the 10 point also must be right.
|
| |
Black
|
White
|
|
6.
|
24/23 12/10 11/10
|
|
|
| Play 6b |
|
|
White to play 41
Candidate Plays Equities
6/1 -0.116
7/3 7/6 -0.191
8/4 8/7 -0.212
|
|
SC:
|
This rollout demonstrates that there is no real benefit
to moving from the 7 point.
If White gives up the 7 point here,
Black just has more flexibility
and White has put his checkers on the wrong spots.
|
| |
Black
|
White
|
|
6.
|
...
|
41: 6/1
|
|
| Play 7a |
|
|
Black to play 61
Candidate Plays Equities
13/6 +0.040
13/7 6/5 +0.010
10/3* -0.097
|
|
SC:
|
Put the spares on the 6 point. Woolsey's 4th law.
|
| |
Black
|
White
|
|
7.
|
61: 13/6
|
|
|
| Play 7b |
|
|
White to play 42
Candidate Plays Equities
7/3 7/5 -0.241
7/1 -0.289
8/4 8/6 -0.327
|
|
SC:
|
Making the ace point would be nice,
but the blot remaining on the 7 point would be a very attractive victim.
|
| |
Black
|
White
|
|
7.
|
...
|
42: 7/3 7/5
|
|
| Play 8a |
|
|
Black to play. Double or roll?
Equity (center cube)
Black 67.5% G 2.4% BG 0.2%
White 32.5% G 2.0% BG 0.1%
Equity (Black): +0.354
Equity (White owns 2 cube)
Black 50.3% G 13.2% BG 0.6%
White 49.7% G 2.7% BG 0.1%
Equity (White): -0.116
Equity (cubeless)
Black 59.8% G 14.3% BG 0.7%
White 40.2% G 10.8% BG 0.4%
Equity (Black): +0.235
|
|
SC:
|
This is not really very close to a double.
Black still has two checkers back which might have difficultly escaping.
White is anchored on the 4 point,
so his racing lead could always come into play.
Black might not have a double even if he escaped one of the back checkers.
|
|
JF:
|
I would not have doubled (level 7 evaluation).
|
| |
Black
|
White
|
|
8.
|
Double -> 2
|
Accept
|
|
| Play 9a |
|
|
Black to play 42
Candidate Plays Equities
7/3* 5/3 +0.204
6/2 5/3* +0.178
10/6 10/8 +0.125
10/6 5/3* +0.100
6/2 23/21 +0.071
|
|
SC:
|
6/2 23/21,
the play made at the table,
gives White too many options.
White will be happy to attack with the right roll
or escape if that possibility comes up.
In the meantime,
the checker on the 2 point is a real weakness.
Hitting gives up the prime,
but White's reply hits are not that strong.
|
| |
Black
|
White
|
|
9.
|
42: 6/2 23/21
|
63: 22/13
|
|
| Play 10a |
|
|
Black to play 21
Candidate Plays Equities
23/21 2/1 +0.111
23/21 6/5 +0.097
|
|
SC:
|
Although the equities are close,
the correct play is clear.
|
| |
Black
|
White
|
|
10.
|
21: 23/21 2/1
|
|
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| Play 10b |
|
|
White to play 62
Candidate Plays Equities
13/5 -0.163
13/7 3/1 -0.168
8/2 8/6 -0.198
8/2 3/1 -0.269
|
|
SC:
|
The question comes up over and over again of how much risk you should take
in order to make a stronger board.
In this example,
the board-building
play is equal to the safe play.
Some factors in favor of taking the risk are:
-
The extra checker on the 7 point will provide flexibility next roll.
Playing safe to the 5 point is quite awkward.
-
It might not be convenient to make the ace point later.
-
The ace point is clearly valuable here,
since the extra checkers on the 3 point are already past Black's anchor.
-
If White is hit,
he probably will have a shot at the blot on Black's 1 point.
-
White will leave only 11 hitting rolls.
Factors in favor of playing safe are:
-
A hit here will change the race.
-
A hit would put the blot behind a 5-out-of-6 prime.
In summary,
the hit is a fairly strong incentive to play safely,
but moving to the 5 point leaves an undesirable follow-up.
The choice is close.
|
| |
Black
|
White
|
|
10.
|
...
|
62: 13/7 3/1
|
|
11.
|
64: 7/1 7/3
|
|
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| Play 11b |
|
|
White to play 42
Candidate Plays Equities
7/1 -0.154
7/3 5/3 -0.243
7/3 8/6 -0.248
|
| |
Black
|
White
|
|
11.
|
...
|
42: 7/1
|
|
| Play 12a |
|
|
Black to play 65
Candidate Plays Equities
21/15 21/16 +0.238
8/2 8/3 +0.192
|
|
SC:
|
When doing rollouts one is often faced with choices
where the results are close and the various moves seem much alike.
Is there a clear winning play here?
Got me.
|
| |
Black
|
White
|
|
12.
|
65: 21/15 21/16
|
|
|
| Play 12b |
|
|
White to play 32
Candidate Plays Equities
5/2 8/6 -0.336
5/2 3/1 -0.350
8/5 8/6 -0.358
8/5 3/1 -0.362
8/3 -0.369
|
|
SC:
|
The equities may be close in rollouts of this type of position,
but the priorities are clear.
You should slot the holes in your board and distribute your other checkers.
This will allow you to build a better board in future rolls,
and having all your points slotted will help you
when the position becomes a race.
The danger of having extra blots when you hit a fly shot
is something you just have to live with.
More likely,
your hitting roll will come later,
when you will be grateful if you have improved your board.
|
| |
Black
|
White
|
|
12.
|
...
|
32: 5/2 8/6
|
|
| Play 13a |
|
|
Black to play 64
Candidate Plays Equities
15/5 +0.333
16/10 6/2 +0.327
16/10 15/11 +0.314
16/6 +0.314
16/10 5/1 +0.239
|
|
SC:
|
This result will surprise a lot a players.
It demonstrates the importance of the race in such positions.
When you move 5/1,
you do significant damage to your chances in the bearoff.
Here that factor more than offsets the problems of an extra blot
and the poorer distribution on the 5 and 6 points.
|
| |
Black
|
White
|
|
13.
|
64: 15/5
|
|
|
| Play 13b |
|
|
White to play 63
Candidate Plays Equities
8/2 21/18 -0.375
8/2 6/3 -0.395
8/2 5/2 -0.443
|
|
SC:
|
A five point board,
a racing lead,
and a Black blot on the 3 point encourage White to run.
Even so,
Black is a strong favorite.
It is difficult to make this kind of split at the table.
|
| |
Black
|
White
|
|
13.
|
...
|
63: 8/2 6/3
|
|
| Play 14a |
|
|
Black to play 54
Candidate Plays Equities
16/11 6/2 +0.266
16/11 5/1 +0.245
6/1 16/12 +0.235
6/1 5/1 +0.199
|
|
SC:
|
This is a position worth looking at.
Each of the three best candidate plays offers a different degree of risk,
yet is about equally good.
Look at the factors favoring each and against each.
|
| |
Black
|
White
|
|
14.
|
54: 16/11 5/1
|
|
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| Play 14b |
|
|
White to play 31
Candidate Plays Equities
6/2 -0.445
6/3 6/5 -0.454
5/1 -0.461
5/2 5/4 -0.461
5/2 3/2 -0.466
|
|
SC:
|
The alternatives are about equal.
Actually I would play 6/3 6/5,
despite the rollout results.
|
| |
Black
|
White
|
|
14.
|
...
|
31: 6/2
|
|
| Play 15a |
|
|
Black to play 42
Candidate Plays Equities
11/7 5/3 +0.409
11/5 +0.406
6/2 5/3 +0.403
6/2 3/1 +0.295
5/1 5/3 +0.106
|
| |
Black
|
White
|
|
15.
|
42: 11/5
|
|
|
| Play 15b |
|
|
White to play 32
Candidate Plays Equities
6/1 -0.443
5/2 3/1 -0.511
|
|
SC:
|
6/1 must be right.
It saves as many home board points as possible.
|
| |
Black
|
White
|
|
15.
|
...
|
32: 6/1
|
|
| Play 16a |
|
|
Black to play 31
Candidate Plays Equities
5/2 3/2 +0.490
5/1 +0.395
|
| |
Black
|
White
|
|
16.
|
31: 5/2 3/2
|
|
|
| Play 16b |
|
|
White to play 21
Candidate Plays Equities
3/1 2/1 -0.476
3/1 3/2 -0.482
|
|
SC:
|
Random equity difference.
|
| |
Black
|
White
|
|
16.
|
...
|
21: 3/1 2/1
|
|
| Play 17a |
|
|
Black to play 22
Candidate Plays Equities
10/6(2) +0.487
5/1 5/3(2) +0.471
10/6 10/8 5/3 +0.469
8/6(2) 5/1 +0.425
|
|
SC:
|
You can't start taking your checkers off until you get them all in.
|
| |
Black
|
White
|
|
17.
|
22: 10/6(2)
|
|
|
| Play 17b |
|
|
White to play 52
Candidate Plays Equities
21/14 -0.560
21/16 3/1 -0.601
|
| |
Black
|
White
|
|
17.
|
...
|
52: 21/14
|
|
18.
|
31: 5/4*/1
|
21: Cannot move
|
|
19.
|
62: 8/2 8/6
|
11: Cannot move
|
|
20.
|
64: 6/Off 6/2
|
61: Cannot move
|
|
| Play 21a |
|
|
Black to play 41
Candidate Plays Equities
6/2 1/Off +0.871
6/2 6/5 +0.852
6/1 +0.825
|
|
SC:
|
This result surprises me.
The general principle to follow in these positions is
to have an even number of checkers on the highest point.
Here taking an extra checker off and the overall awkwardness
in any event make 6/2 1/Off the winner.
|
| |
Black
|
White
|
|
21.
|
41: 6/2 6/5
|
|
|
| Play 21b |
|
|
White to play 64
Candidate Plays Equities
Bar/21 14/8 -0.858
Bar/15 -0.932
|
|
SC:
|
White does not have much chance to win here.
If he runs,
he will have even less.
|
| |
Black
|
White
|
|
21.
|
...
|
64: Bar/21 14/8
|
|
| Play 22a |
|
|
Black to play 21
Candidate Plays Equities
2/Off 1/Off +0.903
5/3 1/Off +0.877
2/Off 2/1 +0.847
5/4*/2 +0.795
5/2 +0.771
|
|
SC:
|
If white rolls big doubles,
Black could be very sorry for not taking two checkers off.
The difference, however, is small.
|
| |
Black
|
White
|
|
22.
|
21: 5/3 1/Off
|
|
|
| Play 22b |
|
|
White to play 22
Candidate Plays Equities
8/4 5/1 -0.906
8/2 3/1 -0.910
8/4 5/3(2) -0.911
8/4 3/1(2) -0.918
8/6 5/1 3/1 -0.922
|
|
SC:
|
Note that the race-oriented play here is a slight winner
over keeping the board together.
This result illustrates again the importance of the race
in these late-game positions.
|
| |
Black
|
White
|
|
22.
|
...
|
22: 8/4 5/3(2)
|
|
| Play 23a |
|
|
Black to play 32
Candidate Plays Equities
3/Off 2/Off +0.936
5/2 5/3 +0.829
|
|
SC:
|
Black has a phantom at the table.
I do not see any follow-up which makes 5/2 5/3 the winner.
|
| |
Black
|
White
|
|
23.
|
32: 5/2 5/3
|
|
|
| Play 23b |
|
|
White to play 31
Candidate Plays Equities
4/1 3/2 -0.873
4/1 21/20 -0.901
4/1 2/1 -0.916
21/17 -0.929
21/18 3/2 -0.932
|
|
SC:
|
White sticks around for the last-ditch shot.
|
| |
Black
|
White
|
|
23.
|
...
|
31: 4/1 3/2
|
|
| Play 24a |
|
|
Black to play 42
Candidate Plays Equities
6/2 6/4* +0.678
6/2/Off +0.669
6/4*/Off +0.657
|
|
SC:
|
An interesting problem at the end of the game.
6/2/Off takes a checker off but leaves 12 shots instead of 11.
6/2 6/4* leaves the minimum number of shots,
gives White an extra crossover,
and has the hope of keeping White on the bar,
but gets no checkers off.
6/4*/Off hits and gets a checker off,
but leaves the most return shots by far.
Here 6/2 6/4* provides the most safety and the hit helps in the race,
so it is the winner.
|
| |
Black
|
White
|
|
24.
|
42: 6/2 6/4*
|
|
|
| Play 24b |
|
|
White to play 62
|
|
White got a shot, but missed.
Black won the race to lead 2-0.
|
The game was recorded on tape by Richard McIntosh,
and transcribed by Steve Clark.
Rollouts were made by Richard McIntosh,
using
JellyFish Analyzer 2.02.
Rollout results show equities
for the player on move.
Candidate plays were better than or
within 0.100 equity of the actual plays,
evaluated at level 7.
Parameter
values for rollouts on moves were:
- level 5
- 7776 games (36x216)
- horizon 7
- seed 6788
Standard deviations of equity estimates were between 0.002 and 0.009.
Parameter values for rollouts on cube decisions were:
- level 5
- 23328 games (36x648)
- full game
- seed 6788
- settlement limit 0.570
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