Early 65: Run or Split?

 I.  Theory

65 run 24/13 is often automatic on the first or second move.  But from the 3rd move move, sometimes in the early game it is right to run 24/13 while other times it is right to split 24/18, 13/8.

How to decide?  Stick covered this concept in a recent Gammon Village article.  He provided several main factors to consider.

(1) Race: 

• Down in the race --> Split
• Up in the race --> Race

Discussion

The race is always an important factor to consider.  The logic here is if you are dwonin the race you want contact while if you are up the race you want to race.  24/13 safely escapes a man, furthering the race game plan.  Splitting with 24/18 seeks contact when you are down in the race, either for an exchange of hits or to simply make the Bar point anchor next turn.

(2) Boardage:

• Better board --> Split
• Worse board --> Run

Discussion 

A blot hitting contest will tend to favor the side with the better board.  Usually in these positions the boardage is 2 to 1 one way or the other.  This may not seem like much but consider you are four times more likely to dance on a 2 point board than a 1 point board.

Also keep in mind that getting hit on opponent's bar point only costs seven pips while if you score a return hit on the opponent's bar point it costs him 18 pips.  Thus an exchange of hits will gain pips in the race.

(3) Midpoint & 8 Point Distribution:

• Stacked midpoint (5 or more) & stripped 8 point (only 2) --> Split
• Midpoint not stacked & 8 point not stripped --> Run

Discussion

This simple observation struck me as rather obvious when Stick wrote it yet I'd never thought of it before! 

Running with 24/13 is less attractive if you are creating a stack on the midpoint.  This is especially true if you are putting a sixth man on the midpoint.

Similarly, Splitting is especially attractive the 8 point is stripped.  Here, playing the 5 from 13/8 reinforces the 8 point and usually creates a visually appealing "nice" balance of builders.

(4) Opponent Outfield Blot:

• Opponent has extra outfield blot or point --> Split
• Opponent does not have outfield blot or point -->  Run

Discussion

Stick writes "the blot or even point in the ourfield" can be a target if they don't use it in some fashion."

I would add splitting to the bar is the classic distraction play.  If the opponent is busy hitting you on his bar point, at least he is distracted from making an inner point.

(5) Other minor Factors:

• Stick mentioned that you are more likely to split when opponent own 10 point than 9 point.  Reason is the general duplication of 3's from the 10 point.

• Opponent advanced anchor.  If opponent has an advanced anchor than you generally want one too.  So splitting may be more desirable than usual.  Please use this one with caution since this is my own rule and not from Stick.

 II. Practice

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(1) 63S-31P-61@-65

is Player 2 score: 0 pip: 151

Unlimited Game Jacoby Beaver

pip: 163 score: 0 is Player 1

XGID=-----BDbB---dE--ac-e----B-:0:0:1:56:0:0:3:0:10

to play 56

1.	XG Roller++	24/18 13/8	eq: -0.215
	Player: Opponent: 44.26% (G:8.16% B:0.25%) 55.74% (G:11.22% B:0.29%)
2.	XG Roller++	24/13	eq: -0.271 (-0.056)
	Player: Opponent: 43.04% (G:6.23% B:0.17%) 56.96% (G:10.98% B:0.22%)
3.	3-ply	13/2	eq: -0.296 (-0.082)
	Player: Opponent: 41.84% (G:9.43% B:0.25%) 58.16% (G:14.47% B:0.54%)

eXtreme Gammon Version: 2.10

This was Stick's first example from his article.

Here all the factors point towards splitting.  Mainly you are down in the race and have the better board so you want contact.  Further, the midpoint/8-point interplay visually looks bad after 24/13 when you get 6 on midpoint and 2 on 8 point.  Contrast that with 24/18, 13/8 when you get a more balanced distro of 5 on midpoint and 3 on 8 point.  Additionally, there is a blot on the 9 point so you get the distraction bonus by splitting.  Finally, note my criterion on anchor also points to splitting as opponent is anchored on your bar point and you are stuck on the ace point.

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(2) 53P-33B-65

is Player 2 score: 0 pip: 155

Unlimited Game Jacoby Beaver

pip: 159 score: 0 is Player 1

XGID=---Bb-D-B---cE-b-c-e----B-:0:0:1:56:0:0:3:0:10

to play 56

1.	XG Roller++	24/18 13/8	eq: -0.189
	Player: Opponent: 46.02% (G:9.25% B:0.33%) 53.98% (G:14.52% B:0.45%)
2.	XG Roller++	24/13	eq: -0.209 (-0.020)
	Player: Opponent: 45.75% (G:7.51% B:0.24%) 54.25% (G:13.57% B:0.36%)
3.	3-ply	13/8 13/7	eq: -0.287 (-0.098)
	Player: Opponent: 42.67% (G:9.55% B:0.29%) 57.33% (G:15.40% B:0.72%)

eXtreme Gammon Version: 2.10

This is Stick's other example from the article.

Here the criteria are mixed but the preponderance are pointing towards splitting.

You are up in the race argues for running but everything else points towards splitting.

You have the better board, the Midpoint/8-point distro and extra outifeld point all points towards splitting.  My extra criterion (opponent's anchor) also points to the split.

******************
(3) 53P-44B-65

is Player 2 score: 0 pip: 151

Unlimited Game Jacoby Beaver

pip: 159 score: 0 is Player 1

XGID=---B-bD-B---cE--bc-e----B-:0:0:1:56:0:0:3:0:10

to play 56

1.	XG Roller++	24/13	eq: -0.352
	Player: Opponent: 42.36% (G:5.52% B:0.16%) 57.64% (G:14.05% B:0.30%)
2.	XG Roller++	24/18 13/8	eq: -0.356 (-0.004)
	Player: Opponent: 42.25% (G:6.79% B:0.21%) 57.75% (G:15.38% B:0.41%)
3.	3-ply	13/8 13/7	eq: -0.435 (-0.082)
	Player: Opponent: 39.30% (G:7.30% B:0.23%) 60.70% (G:16.59% B:0.69%)

eXtreme Gammon Version: 2.10

I found this one on the forums. You can find discussion from this thread. http://www.bgonline.org/forums/webbbs_config.pl?read=114804

This is similar to the above problem. Splitting is probably correct despite the above evaluation.  Dmitriy posted a rollout showing split correct by .017

Probably the reason the split is less correct than in #2 is opponent has the 9 point rather than 10 point.

Dmitriy writes:  (Note Blue refers to you and White the opponent)

This is XG1 rollout.

Race is basically even after the roll, so running play doesn't gain much. If Blue runs, he hopes that he will roll another running number before White primes him in. By splitting he stays connected and puts a spare from overstocked mid point to stripped 8pt. White has an advanced anchor,so by splitting Blue makes a bid for an advanced anchor himself, which would equalize the game. 18pt blot is exposed to plenty of shots, but often he has return hits from the bar or rolls like 54 and 43 that make an anchor. If he splits and White rolls 52 or 41 he is getting hit, but White would make 4 or 5pt if Blue chose to run instead. If White rolls 42 or 31 he should not hit [hit is a blunder], but build his home board instead. It is easy to see that after these sequences split gains a lot as he will have plenty of numbers to anchor on 18pt. Split also gives White opportunity to make more mistakes. With 32 he should not hit, but I think a lot of humans will. With 63 White should hit and slot 4pt [he would be better of by making 3pt if Blue run].

***************
(4) 31P-21S-65

is Player 2 score: 0 pip: 164

Unlimited Game Jacoby Beaver

pip: 163 score: 0 is Player 1

XGID=-aa--BD-B---dEa--c-e----B-:0:0:1:56:0:0:3:0:10

to play 56

1.	XG Roller++	24/18 13/8	eq: +0.327
	Player: Opponent: 57.60% (G:16.82% B:0.82%) 42.40% (G:10.53% B:0.38%)
2.	XG Roller++	24/13	eq: +0.319 (-0.008)
	Player: Opponent: 58.30% (G:13.63% B:0.57%) 41.70% (G:9.58% B:0.28%)
3.	4-ply	13/2*	eq: +0.240 (-0.087)
	Player: Opponent: 54.84% (G:19.08% B:0.94%) 45.16% (G:11.58% B:0.65%)

eXtreme Gammon Version: 2.10

This is an old one from the forums (2007).

http://www.bgonline.org/forums/webbbs_config.pl?noframes;read=114706

The rollout in the link seems to match the ++ eval.  Namely Split but essentially a toss up.

Looking at Stick's criteria:

Up in the race points to racing

Better board, Mid/8 Distro, and outfield blot point to splitting.

****************
(5) 31P-53P-65

is Player 2 score: 0 pip: 159

Unlimited Game Jacoby Beaver

pip: 163 score: 0 is Player 1

XGID=-b---BD-B---eE---b-d--b-B-:0:0:1:56:0:0:3:0:10

to play 56

1.	XG Roller++	24/13	eq: +0.255
	Player: Opponent: 56.68% (G:14.25% B:0.63%) 43.32% (G:11.39% B:0.35%)
2.	XG Roller++	24/18 13/8	eq: +0.251 (-0.003)
	Player: Opponent: 56.26% (G:16.89% B:0.92%) 43.74% (G:13.20% B:0.50%)
3.	3-ply	13/8 13/7	eq: +0.143 (-0.112)
	Player: Opponent: 53.67% (G:17.12% B:0.79%) 46.33% (G:13.18% B:0.77%)

eXtreme Gammon Version: 2.10

Another old one from the forums.  An old GNU rollout has running best by .014

http://www.bgonline.org/forums/webbbs_config.pl?noframes;read=114632

Looking at Stick's criteria:

Race and no extra outfield blots/points argue for racing.

"Better" board and mid/8 point distro argue for splitting so it's close.

I put better board in quotes since the actual boardage is 2 to 2.  But surely your 5 point is better than opponent's 3 point. 

No wonder it's close but note if you count the boardage as a wash than the preponderance of criteria is slightly in favor of running, consistent with the rollout.