Game #13
Open Division Final
San Mateo, California
September 21, 1997
11 Point Match
Carmi Brandis (Blue) vs. Paul Tanenbaum (White)
Score: 5 - 8
Analysis by Ron Karr
An all-star line-up is on hand for September's featured match. Carmi
Brandis and Paul Tanenbaum are charter BACKGAMMON BY THE BAY members,
and each has participated in every 1997 BGBB tourney. They concretely
disprove the adage that nice guys finish last (well actually, in
backgammon it's good to finish last, but you know what I mean). Ron
Karr takes a brilliant turn in the game analyst's seat, particularly in
his ability to put into words the lessons JellyFish has to impart.
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Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
24/21 13/11 +0.005 50.3% 12.0% 0.4% 49.7% 12.1% 0.3%
13/10 24/22 +0.002 49.9% 12.1% 0.3% 50.1% 11.7% 0.3%
13/10 13/11 -0.003 49.6% 13.0% 0.4% 50.4% 12.6% 0.4%
13/8 -0.021 49.2% 11.9% 0.3% 50.8% 12.4% 0.3%
24/21 24/22 -0.022 49.4% 10.7% 0.3% 50.6% 11.7% 0.3%
8/5 13/11 -0.036 48.5% 12.4% 0.4% 51.5% 12.9% 0.5%
13/10 6/4 -0.044 48.4% 11.9% 0.3% 51.6% 12.9% 0.5%
24/21 8/6 -0.061 47.8% 11.1% 0.3% 52.2% 12.7% 0.4%
24/21 6/4 -0.064 47.7% 10.9% 0.3% 52.3% 12.6% 0.4%
6/3 13/11 -0.073 47.3% 11.8% 0.3% 52.7% 13.5% 0.5%
13/10 8/6 -0.076 47.0% 11.8% 0.3% 53.0% 13.2% 0.4%
8/5 24/22 -0.092 46.6% 10.9% 0.3% 53.4% 13.0% 0.4%
6/3 24/22 -0.093 46.6% 10.8% 0.3% 53.4% 13.2% 0.4%
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RK:
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After an initial flurry, White enters and makes the 5 point. With the last
ace, splitting the back checkers is constructive with little risk. Slotting
the bar point could be right if you were desperate to make a prime, but
here White is in good shape anyway and doesn't need to take the risk.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/23 6/5(2)* +0.392 63.6% 19.5% 1.0% 36.4% 8.4% 0.2%
Bar/24 6/5(3)* +0.351 62.2% 19.0% 1.0% 37.8% 9.2% 0.3%
Bar/24 8/7 6/5(2)* +0.329 61.6% 18.9% 1.1% 38.4% 9.8% 0.4%
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RK:
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Blue enters and has no attractive options with the 6. Since White has the
better board, minimizing contact with 22/16 seems best. If not hit, Blue
may be able to make something next time.
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/16 -0.421 35.5% 8.0% 0.2% 64.5% 20.3% 1.1%
Bar/22 24/18 -0.446 35.8% 8.1% 0.3% 64.2% 23.0% 1.5%
Bar/22 11/5 -0.492 33.8% 7.4% 0.2% 66.2% 22.7% 1.7%
Bar/22 10/4 -0.496 33.5% 7.5% 0.2% 66.5% 22.8% 1.6%
Bar/22 8/2* -0.503 33.5% 7.5% 0.2% 66.5% 23.2% 1.8%
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RK:
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After hitting, White has several choices with the 1. Slotting the bar
point is an attempt to make a quick prime, but gives Blue several return
shots from the bar. If White makes a quieter play, Blue has few good
numbers, and White is well positioned to do something good next time.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
13/9* 23/22 +0.469 65.6% 22.4% 1.4% 34.4% 8.0% 0.2%
13/9* 6/5 +0.442 64.8% 21.8% 1.3% 35.2% 8.3% 0.3%
13/9* 9/8 +0.436 64.9% 20.6% 1.1% 35.1% 7.8% 0.2%
13/9* 24/23 +0.437 64.7% 21.6% 1.3% 35.4% 8.3% 0.3%
13/9* 8/7 +0.415 64.2% 21.1% 1.3% 35.8% 8.9% 0.3%
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RK:
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A choice of hits with the 6: hitting on the bar point removes a more
valuable slot and gains slightly more ground in the race.
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/22 24/18* -0.228 42.3% 11.0% 0.5% 57.7% 17.9% 1.1%
Bar/16* -0.296 39.8% 10.7% 0.5% 60.2% 19.2% 1.1%
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RK:
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With a superior board and with the opponent having a number of builders in
place to make new points, it's tempting for White to hit loose on the 3
point. The problem is that Blue has lots of good numbers after this play
anyway: 3s and 2s hit back, and 6s make the defensive bar point. White
does better to quietly make the useful 9 point and see what Blue does.
Blue can make a home board point or a defensive point, but not both; either
way White has a flexible position with good opportunities.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/22 13/9 +0.155 55.5% 14.5% 0.5% 44.5% 10.2% 0.3%
Bar/21 6/3* +0.091 53.4% 15.8% 0.9% 46.6% 13.5% 0.8%
Bar/21 24/21 +0.067 52.0% 13.0% 0.4% 48.0% 10.3% 0.3%
Bar/22 9/5 +0.062 51.9% 13.9% 0.5% 48.1% 11.6% 0.4%
Bar/21 9/6 +0.045 51.3% 14.4% 0.6% 48.7% 12.7% 0.5%
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RK:
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Blue enters with the 4 and again has a choice of hits. He's clearly ahead
in the race, but is vulnerable with 5 blots and no board. Hitting the blot
on the 3 point seems natural, since the 3 point is probably more valuable
than the 9 point and costs Blue more pips. However, this is an interesting
situation: by hitting on the 3 point, the checker on 9 remains as a builder
or a slot. By NOT hitting the blot on the 3 point, it remains a target for
Blue. If White covers it, then he isn't hitting Blue, so Blue may be able
to consolidate. If White hits somewhere else, then Blue has a double shot
from the bar.
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/21 18/16* -0.032 48.2% 14.4% 0.9% 51.8% 14.1% 0.9%
Bar/21 24/22* -0.115 45.6% 12.7% 0.7% 54.4% 15.1% 0.9%
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RK:
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Now White has a choice of hits: on 15, 14, 7 or 3! Whichever way, Blue will
have numerous return shots. The usual choice here is to hit on the
opponent's side of the board, gaining more ground in the race and reducing
his offensive potential, and this position appears to be no exception.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/14* +0.176 56.7% 15.1% 0.9% 43.3% 11.1% 0.6%
Bar/20 21/15* +0.175 56.6% 15.3% 0.9% 43.4% 11.2% 0.7%
Bar/20 13/7* +0.128 55.3% 15.5% 1.0% 44.7% 13.3% 0.9%
Bar/20 9/3* +0.052 52.2% 13.9% 0.8% 47.8% 13.1% 0.8%
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RK:
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The same principle applies:
Hit on the opponent's side of the board.
It's close to grab the advanced anchor and attack inside on the 4 point.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/22 20/15* +0.086 53.9% 14.4% 0.8% 46.1% 13.5% 0.9%
Bar/20 7/4* +0.063 52.7% 14.0% 0.7% 47.3% 13.0% 0.7%
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RK:
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Finally, Blue can consolidate by making an anchor and an outfield point.
What I find interesting in the results is that making the 16 point is
almost as good, despite leaving a much looser position. It shows the
importance of outfield coverage and flexibility when White has many
checkers back and not a big offensive threat yet.
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/21 16/11 -0.050 47.2% 12.6% 0.6% 52.8% 12.3% 0.4%
Bar/16 -0.078 47.1% 11.9% 0.6% 52.9% 14.0% 0.5%
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RK:
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White has a choice of anchors: if he makes the 20 point, he has to leave
two outfield blots; or he can make the 21 point while safetying one of the
blots. Grabbing the best anchor appears to be worth it, since many of
Blue's hitting numbers force him to break a good point.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
23/20 22/20 -0.033 49.7% 10.9% 0.3% 50.3% 13.5% 0.7%
24/21 15/13 -0.058 48.6% 10.5% 0.3% 51.4% 13.2% 0.5%
24/21 7/5 -0.061 48.3% 10.8% 0.3% 51.7% 13.2% 0.5%
24/21 23/21 -0.076 48.5% 10.3% 0.3% 51.5% 14.6% 0.7%
24/21 22/20 -0.095 48.2% 10.2% 0.3% 51.8% 15.6% 0.8%
21/18 24/22 -0.104 48.0% 10.3% 0.3% 52.0% 16.1% 0.8%
24/21 13/11 -0.108 48.4% 10.4% 0.3% 51.6% 17.3% 1.1%
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RK:
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This roll shows why it wasn't so bad for White to leave 2 blots: it's not
correct for Blue to hit both of them when he has a chance! It's certainly
tempting to put two checkers in the air, but Blue has to break two good
points to do so, and he may not have time to put everything back together.
(If he hits on the 10 point, then 3s are duplicated to cover it and make
the bar point.) He's better off just locking up the bar point, which
interferes with White's prime-building, and play from there.
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
22/18* 21/18 +0.102 53.4% 13.0% 0.5% 46.6% 9.8% 0.2%
22/18* 13/10* +0.049 49.9% 15.1% 0.8% 50.1% 10.6% 0.3%
8/4* 21/18* +0.046 50.4% 14.6% 0.8% 49.6% 11.2% 0.4%
Level 6:
Blue White
Candidate Plays Win G/BG BG Equity Win G/BG BG
22/18* 21/18 +0.092 54.1% 14.3% 0.4% 45.9% 13.1% 0.6%
22/18* 13/10* +0.050 50.8% 15.9% 0.6% 49.2% 12.7% 0.4%
8/4* 21/18* +0.004 49.5% 15.3% 0.5% 50.5% 13.6% 0.8%
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RK:
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Blue can accomplish several good things with this roll: making a good
blocking point (the 10) and putting a second checker on the bar while
starting the 4 point (making efficient use of the stack on the 6). If he
can cover the 4 point he'll be in fine shape, while even if hit he should
have little trouble recirculating. Any other play doesn't accomplish as
much. Remaking the midpoint looks innocuous, but it really lets White off
the hook.
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
13/10 6/4* +0.160 54.0% 16.4% 0.8% 46.0% 9.0% 0.2%
13/10 18/16 +0.139 53.6% 15.4% 0.7% 46.4% 9.1% 0.2%
21/18 6/4* +0.117 52.6% 15.8% 0.8% 47.4% 9.8% 0.3%
21/18 10/8 +0.095 52.3% 14.4% 0.6% 47.7% 9.8% 0.2%
21/18 13/11 +0.059 51.4% 13.0% 0.5% 48.6% 10.2% 0.2%
6/4*/1* +0.050 49.7% 16.2% 0.7% 50.3% 10.9% 0.3%
18/15 6/4* +0.049 50.0% 15.1% 0.8% 50.0% 10.7% 0.4%
13/10 8/6 +0.047 50.2% 14.5% 0.7% 49.8% 10.6% 0.3%
10/7 6/4* +0.044 50.0% 15.1% 0.8% 50.0% 10.9% 0.4%
18/13 +0.017 49.5% 13.0% 0.6% 50.5% 10.6% 0.3%
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RK:
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Blue enters and runs out with the same checker, keeping the anchor.
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/16 -0.032 48.3% 11.4% 0.5% 51.7% 11.5% 0.3%
Bar/22 21/15 -0.062 47.8% 11.2% 0.5% 52.2% 13.0% 0.4%
Bar/22 8/2 -0.115 45.2% 10.7% 0.4% 54.8% 12.7% 0.4%
Level 6:
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/16 -0.041 48.0% 12.0% 0.5% 52.0% 12.0% 0.5%
Bar/22 21/15 -0.126 45.8% 11.6% 0.5% 54.2% 15.6% 0.8%
Bar/22 8/2 -0.148 44.8% 10.5% 0.3% 55.2% 14.6% 0.6%
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RK:
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A good roll, hitting and adding a new point to the blockade.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
15/9* 13/9 +0.164 56.5% 13.0% 0.4% 43.5% 9.6% 0.4%
21/15 13/9* +0.078 53.4% 12.0% 0.3% 46.6% 11.0% 0.5%
15/9* 22/18 +0.048 52.1% 11.5% 0.3% 47.9% 10.8% 0.4%
15/9*/5 +0.043 51.5% 11.9% 0.3% 48.5% 10.4% 0.4%
Level 6:
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
15/9* 13/9 +0.164 56.0% 14.3% 0.5% 44.0% 9.9% 0.6%
21/15 13/9* +0.124 54.2% 13.9% 0.4% 45.8% 10.1% 0.2%
15/9*/5 +0.066 52.0% 13.4% 1.0% 48.0% 11.4% 0.3%
15/9* 22/18 +0.042 52.0% 12.9% 0.5% 48.0% 12.5% 0.6%
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RK:
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At first glance it's not appealing to break the anchor, but the alternative
is definitely worse, putting a checker deep in the home board and stripping
the 8 point. Blue needs to preserve flexibility, and White still doesn't
have great attacking possibilities.
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/22 21/15 -0.190 43.5% 10.4% 0.5% 56.5% 16.3% 0.6%
Bar/22 8/2 -0.265 39.9% 8.6% 0.3% 60.1% 14.7% 0.5%
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RK:
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A number of reasonable plays here, none of which accomplishes much as
double-4s go. White chooses to advance the anchor, which is fine since
Blue has no board, and keeps a flexible position.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
20/16(2) 13/9(2) +0.216 58.5% 15.1% 0.5% 41.5% 10.7% 0.3%
24/16 20/16(2) +0.208 59.1% 12.9% 0.4% 40.9% 10.4% 0.2%
24/16 13/9(2) +0.203 57.7% 14.1% 0.4% 42.3% 9.4% 0.3%
22/18 20/16(2) 13/9 +0.198 58.7% 14.2% 0.5% 41.3% 11.8% 0.5%
24/16 22/18 13/9 +0.194 58.0% 14.3% 0.5% 42.0% 11.0% 0.5%
22/18 13/5 13/9 +0.182 56.6% 15.0% 0.5% 43.4% 10.2% 0.4%
24/20 22/18 13/9(2) +0.179 56.8% 13.2% 0.3% 43.2% 9.0% 0.3%
24/16 20/16 13/9 +0.177 57.7% 13.9% 0.5% 42.3% 11.6% 0.5%
24/16 22/18 20/16 +0.174 58.2% 12.6% 0.4% 41.8% 11.5% 0.4%
24/16 13/5 +0.169 56.5% 14.8% 0.5% 43.5% 10.9% 0.4%
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RK:
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Another play with lots of reasonable candidates.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
22/20 21/20 16/15 +0.322 63.4% 11.8% 0.2% 36.6% 6.5% 0.1%
22/21 16/15(3) +0.313 63.1% 12.5% 0.3% 36.9% 7.4% 0.1%
22/21 13/10 +0.310 63.1% 12.8% 0.3% 36.9% 8.2% 0.2%
22/21 16/15 13/11 +0.307 63.0% 12.8% 0.3% 37.0% 8.3% 0.2%
22/20 21/20 13/12 +0.297 62.4% 11.4% 0.2% 37.6% 6.6% 0.1%
22/21 16/15 13/12(2) +0.292 62.4% 12.4% 0.3% 37.6% 8.0% 0.2%
22/11 16/15 8/7(2) +0.291 62.3% 12.0% 0.3% 37.7% 7.7% 0.2%
22/21 16/15(2) 13/12 +0.289 62.4% 12.4% 0.3% 37.6% 8.5% 0.2%
22/21 13/11 13/12 +0.288 62.0% 12.6% 0.3% 38.0% 7.9% 0.2%
22/21 13/12 8/7(2) +0.284 62.1% 12.0% 0.3% 37.9% 7.9% 0.2%
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RK:
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White enters and keeps all his points. Diversifying with 13/11 is
reasonable too.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/20 +0.097 55.4% 8.9% 0.1% 44.6% 10.0% 0.2%
Bar/22 13/11 +0.077 55.1% 9.7% 0.2% 44.9% 12.1% 0.3%
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RK:
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It would be easy to reflexively make the bar point here, but making the 10
and starting the 3 accomplishes more.
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
6/3 11/10 -0.082 45.6% 9.8% 0.2% 54.4% 9.2% 0.1%
10/7 8/7 -0.109 44.2% 9.3% 0.2% 55.8% 8.6% 0.1%
10/6 -0.173 41.7% 8.6% 0.1% 58.3% 9.2% 0.1%
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RK:
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20/11 keeps all points and provides a new builder for the 7 and 10
points. White doesn't have to worry about leaving indirect shots because
of Blue's weak board.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
20/11 +0.125 56.0% 9.5% 0.2% 44.0% 9.0% 0.2%
13/8 20/16 +0.089 54.4% 9.5% 0.1% 45.6% 9.4% 0.2%
16/11 16/12 +0.075 53.7% 9.3% 0.2% 46.3% 9.2% 0.2%
13/8 13/9 +0.049 52.4% 10.1% 0.2% 47.6% 10.0% 0.2%
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RK:
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Another play with lots of choices. First, should White stay on the 20
point? Absolutely, since he's behind in the race and Blue is stripped.
Then what? 11/3 leaves no shots but puts a checker out of play, giving
Blue incentive to run when he really needs to. 11/7 9/7(2) is also safe
and gives better attacking chances if Blue runs. 13/7 13/11 leaves a
direct shot, but White would have reasonable return shots, and a chance to
make a 5-prime, which would greatly improve his equity.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
13/7 13/11 +0.079 54.7% 9.8% 0.2% 45.3% 11.2% 0.2%
11/7 9/7(2) +0.075 53.6% 9.5% 0.2% 46.4% 9.1% 0.1%
11/3 +0.058 52.5% 10.4% 0.2% 47.5% 9.6% 0.2%
13/9(2) +0.054 52.7% 9.6% 0.2% 47.3% 9.6% 0.2%
13/11(2) 9/7(2) +0.051 52.3% 9.4% 0.2% 47.7% 9.0% 0.1%
13/5 +0.048 52.9% 9.4% 0.2% 47.1% 10.2% 0.2%
20/18(2) 13/11(2) +0.022 52.8% 6.8% 0.1% 47.2% 10.3% 0.1%
20/18(2) 13/9 +0.021 53.3% 7.2% 0.1% 46.7% 11.7% 0.1%
20/18(2) 9/7(2) -0.005 51.9% 7.2% 0.1% 48.1% 11.3% 0.1%
Level 6:
White Blue
Candidate Plays Win G/BG BG Equity Win G/BG BG
11/7 9/7(2) +0.105 54.7% 10.8% 0.5% 45.3% 9.7% 0.5%
13/7 13/11 +0.091 54.8% 13.2% 0.6% 45.2% 13.8% 0.4%
20/18(2) 13/11(2) +0.067 54.5% 9.0% 0.5% 45.5% 11.5% 0.3%
13/9(2) +0.064 53.1% 11.5% 0.4% 46.9% 11.5% 0.1%
13/11(2) 9/7(2) +0.062 52.6% 10.2% 0.4% 47.4% 9.3% 0.1%
11/3 +0.055 52.3% 12.8% 0.4% 47.7% 12.1% 0.2%
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RK:
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Clearing the 11 point gives Blue some needed flexibility. Trying to hold
all the outer points with 6/1 2/1 would be unrealistic.
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
11/6 11/10 -0.177 41.8% 7.5% 0.1% 58.2% 8.8% 0.1%
6/1 2/1 -0.227 40.2% 8.2% 0.1% 59.8% 11.1% 0.2%
8/3 8/7 -0.252 38.8% 8.2% 0.1% 61.2% 11.0% 0.2%
8/2 -0.265 38.4% 8.3% 0.1% 61.6% 11.6% 0.2%
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RK:
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Should White continue to leave a direct shot? Yes, the upside from being
able to make the bar point, plus the return shots if hit, make it clearly
better than playing the "safer" 7/2 11/8. Basically, White gains from
keeping all his checkers in play.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
16/11 16/13 +0.071 54.9% 8.3% 0.1% 45.1% 10.8% 0.2%
11/6 11/8 +0.069 54.0% 9.7% 0.2% 46.0% 10.8% 0.2%
7/2 11/8 -0.001 50.5% 9.3% 0.2% 49.5% 10.3% 0.2%
16.8 -0.010 52.2% 8.4% 0.2% 47.8% 13.7% 0.3%
11/3 -0.029 51.3% 9.3% 0.2% 48.7% 14.7% 0.4%
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Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
21/18* 10/8 +0.123 50.8% 19.3% 0.6% 49.2% 9.0% 0.2%
21/18* 6/4 +0.017 47.8% 17.1% 0.5% 52.2% 11.1% 0.3%
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RK:
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Things went very well for Blue: he hit and White fanned. After 18/13,
should he keep the checker going or play the apparently more awkward 8/6?
The latter play has definite advantages:
- If White fans, Blue has a chance to hit the other checker.
- If White enters and doesn't hit back, he'll have to try to safety his
outfield checker. Then Blue's blot on 13 will be relatively safe and he
can concentrate on escaping his back checker. After 18/11, on the other
hand, the checker on 11 will remain a target if not hit this time.
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
18/13 8/6 +0.274 57.1% 19.8% 0.4% 42.9% 6.8% 0.1%
18/11 +0.204 54.8% 17.6% 0.4% 45.2% 6.9% 0.1%
18/13 6/4 +0.156 53.2% 17.9% 0.4% 46.8% 8.8% 0.2%
18/13 10/8 +0.147 52.2% 18.4% 0.4% 47.8% 8.3% 0.2%
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RK:
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Entering and making the 4 point is clear. With the fourth 4,
slotting the bar point leaves 6 shots but threatens to add a key point to
White's blockade; it appears to be worth the risk.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/21 11/7 8/4(2)* +0.145 58.1% 13.0% 0.4% 41.9% 14.6% 0.5%
Bar/21 13/9 8/4(2)* +0.124 55.1% 12.0% 0.3% 44.9% 9.9% 0.2%
Bar/21 9/5 8/4(2)* +0.035 52.7% 12.5% 0.4% 47.3% 14.3% 0.5%
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RK:
|
Blue is pretty much forced to hit or risk being clobbered. White's next
roll is crucial.
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/22 10/4* -0.179 41.0% 17.6% 0.7% 59.0% 17.2% 0.9%
Bar/22 8/2 -0.255 37.9% 13.6% 0.5% 62.1% 14.7% 0.4%
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RK:
|
Blue wins the gamble and should double. Most numbers cover the 4 point,
and White has two outfield blots to worry about. If things go well, Blue
could definitely lose his market (if he hasn't already). The rollouts
indicate it's a close decision whether to take, which means it's clear to
double. The match score makes it even clearer.
|
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JF:
|
I would have doubled (level 7 evaluation).
Blue White
Level 7 Evaluation Equity Win G/BG BG Win G/BG BG
Cubeless +0.577 63.6% 34.4% 1.2% 36.4% 5.1% 0.1%
Level 5 Rollouts Equity Win G/BG BG Win G/BG BG
Cube centered +0.622 72.4% 17.4% 0.5% 27.6% 0.4% 0.0%
Blue owns cube +0.719 78.9% 17.9% 0.5% 21.1% 4.2% 0.2%
White owns cube +0.448 54.7% 34.9% 1.0% 45.3% 0.5% 0.0%
Cubeless +0.581 63.2% 36.8% 1.1% 36.9% 6.1% 0.2%
Level 6 Rollouts Equity Win G/BG BG Win G/BG BG
Cubeless +0.556 62.6% 36.5% 1.0% 37.4% 6.8% 0.3%
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RK:
|
Things went quite well for White, but here he misses a double shot. It's
tempting to hit inside to try to get another opportunity at the outfield
blots, but that's too optimistic. Getting hit back is bad since Blue has
the better board, and there are no direct covers for the 2 point if that
blot is missed. Besides, White has a fine alternative in making the bar
point, which increases the pressure on the back checker. After 11/7,
cleaning up a blot with 14/9 seems obvious, but the chance of making the
6-prime is just about worth the extra shots after 13/8.
White Blue
Candidate Plays Equity Win G/BG BG Win G/BG BG
14/9 11/7 -0.036 51.1% 5.4% 0.1% 48.9% 11.2% 0.2%
13/8 11/7 -0.038 56.2% 6.3% 0.2% 43.8% 22.0% 0.7%
7/2* 13/9 -0.124 47.8% 9.2% 0.3% 52.2% 17.1% 0.4%
11/6 11/7 -0.131 48.3% 6.0% 0.2% 51.7% 15.7% 0.3%
7/2* 14/10 -0.149 48.5% 8.7% 0.2% 51.5% 20.3% 0.7%
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RK:
|
Blue performs, then has an interesting decision with the 4. As with play
18, staying back with the blot on 13 is correct to threaten White's blot.
At first glance, the difference between 6/2 and 8/4 seems surprisingly
large. It's sometimes right to keep a spare on the 8 point to allow 6s and
5s to play safely. But here, Blue can use 5s and 6s to run the back
checker so that won't be necessary. So 8/4 is clear because it puts the
new inside builder in a better place, plus gaining a crossover in the race
for a gammon.
Blue White
Candidate Plays Equity Win G/BG BG Win G/BG BG
Bar/23* 8/4 +0.455 60.9% 28.4% 0.6% 39.1% 5.2% 0.1%
Bar/23* 6/2 +0.399 59.4% 26.6% 0.5% 40.6% 5.9% 0.1%
Bar/23* 13/9 +0.353 58.1% 24.2% 0.5% 41.9% 5.5% 0.1%
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RK:
|
After White fans, Blue is in great shape. He shouldn't have much trouble
escaping, and has 13 numbers to put a second checker in the air. It's far
too dangerous for White to take this cube. That being the case, should
Blue consider playing for the gammon? According to the rollouts, the
gammon chances aren't twice as great as the losing chances, so overall the
odds aren't right. Can Blue afford to take a roll to see which way the
wind blows? If he hits the second checker he'll be glad, but if he misses
and White enters immediately, White has definite counterattacking chances,
so Blue could regret not doubling. So cashing is probably right.
|
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JF:
|
I would have doubled (level 7 evaluation).
Blue White
Level 7 Evaluation Equity Win G/BG BG Win G/BG BG
Cubeless +0.743 68.7% 39.1% 1.0% 31.3% 3.3% 0.0%
Level 5 Rollouts Equity Win G/BG BG Win G/BG BG
Cube centered +0.855 81.2% 23.1% 0.2% 18.8% 0.1% 0.0%
Blue owns cube +0.918 85.2% 23.4% 0.2% 14.8% 2.3% 0.1%
Cubeless +0.806 71.5% 40.8% 0.5% 28.5% 3.6% 0.1%
Level 6 Rollouts Equity Win G/BG BG Win G/BG BG
Cubeless +0.801 71.1% 41.4% 0.4% 28.9% 4.0% 0.2%
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|
|
|
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JF:
|
I would have not have accepted (level 7 evaluation).
White Blue
Level 7 Evaluation Equity Win G/BG BG Win G/BG BG
Cubeless -0.743 31.3% 3.3% 0.0% 68.7% 39.1% 1.0%
Level 5 Rollouts Equity Win G/BG BG Win G/BG BG
Cube centered -0.855 18.8% 0.1% 0.0% 81.2% 23.1% 0.2%
White owns cube -0.697 35.0% 0.2% 0.0% 65.0% 39.5% 0.5%
Cubeless -0.806 28.5% 3.6% 0.1% 71.5% 40.8% 0.5%
Level 6 Rollouts Equity Win G/BG BG Win G/BG BG
Cubeless -0.801 28.9% 4.0% 0.2% 71.1% 41.4% 0.4%
|
|
|
Blue went on to win the match, 11-10.
|
The game was recorded on tape and transcribed by Richard McIntosh.
Rollouts were made by Richard McIntosh,
using
JellyFish Analyzer 3.0.
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 checker plays were:
- level 5
- 7776 games (36x216)
- horizon 7
- seed 921
Standard deviations of equity estimates were between 0.002 and 0.011,
generally 0.004.
On plays 8a, 10a, 10b, and 15b, additional level 6 rollouts were done.
Parameter
values for level 6 rollouts on checker plays were:
- level 6
- 216 games (36x6)
- full game
- seed 921
Parameter values for level 5 rollouts on cube decisions were:
- level 5
- 23328 games (36x648)
- full game
- seed 921
- settlement limit 0.550
Parameter values for level 6 rollouts on cube decisions were:
- level 6
- 1296 games (36x36)
- full game
- seed 921
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BackGammon By the Bay
