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August 25, 2012


Below are selected descisons / errors from an online match against Lyurix.

I trail 7 away 5 away and have 65 to play.  Do you stay or do you go?

is Lyurix

score: 2
pip: 129
7 point match
                          pip: 139
score: 0

is Chutzpah
to play 65

1.XG Roller+24/13eq: -0.186
42.67% (G:1.24% B:0.01%)
57.33% (G:1.48% B:0.04%)
2.XG Roller+13/8 10/4eq: -0.210 (-0.025)
41.82% (G:4.02% B:0.03%)
58.18% (G:4.93% B:0.18%)
3.4-ply24/18 13/8eq: -0.195 (-0.010)
42.18% (G:1.28% B:0.01%)
57.82% (G:1.50% B:0.05%)
eXtreme Gammon Version: 2.02, MET: Kazaross XG2

I stayed back, moving 13/8, 10/4, on the logic that I am behind in the race and my man on the ace point is usefully guarding the holes on Lyurix's inner board.  And this is true, as far it goes.

Here is my general thinking on this point (as of this moment only!!) --

  • Staying back on the ace point plays for maximum contact, and generates the most shots
  • The more open points in the home board, the more effective this lone back man is.
  • Staying back on the ace point gets you gammoned the most often.   Sometimes you can be pointed on, or hit loose and dance - in which case you could stay on the bar a long time and get G'balled.
  • The more points the opponent fills in, the more danger your lone back man is in.
  • A rule of thumb - when the opponent fills in all the points in front of the back blot it is too dangerous, and time to get the hell out of there if you can.
  • Keep an eye on the race - even if you are behind jumping up the the anchor can be still be correct if the race is a legitimate option.
 The best move in this exact position was 24/13.  The last point on the race seems to be the key factor here.  After the play I am only slightly behind in the race so racing is a legitimate option.  While I am behind, I have the midpoint contact plus the chance to get lucky and win the race.  In particular, I need to position myself so that 55 or 44 are truly excellent roles for me. 

I trail 7 away 5 away and am on roll.  Cube action?

is Lyurix

score: 2
pip: 83
7 point match
                          pip: 75
score: 0

is Chutzpah
on roll, cube action?

Analyzed in 4-ply No double Double/Take
  Player Winning Chances: 73.29% (G:0.00% B:0.00%) 73.29% (G:0.00% B:0.00%)
  Opponent Winning Chances: 26.71% (G:0.00% B:0.00%) 26.71% (G:0.00% B:0.00%)
  Cubeless Equities +0.466 +0.945
Cubeful Equities
     No double:+0.750 (-0.062)
xg Double/Take:+0.812
     Double/Pass:+1.000 (+0.188)
Best Cube action: Double / Take
eXtreme Gammon Version: 2.02, MET: Kazaross XG2

I doubled and Lyruix took. Not too difficult. I posted it because I wanted to practice the various methods for estimating race cube actions.

Probably the easiest is just 10% + 2 pips. 

Per Doug Zare, being on roll with a 10% lead means you win about 75% of the time.  This applies for race of 50-120 pips. 

10% + 2 pips indicates the point of last take and 10% - 2 pips would be initital double point, 10% - 1 pip the redouble point.

10% of 75 is 7.5, so I can double with 5.5 pip lead and he can take up to 9.5 pips behind. 

Thus, Double / Take is the cube action.

Trice is similar. 

For races 62 pips or greater, point of last take is 10% of leader count + 1 pip,  round up.  Double within 3 pips of last take and Redouble within 2 pips.

For races of 62 pips or sammler, point of last take is (leader count - 5 ) / 7, round down.  Double within 3 pips of last take and Redouble within 2 pips.

I was always a bit confused on this, but I believe Trice also recommends using Ward adjustments for wastage.  Apply the adjustments to both sides, and then use the Trice formula to estimate cue actions.

** Ward Adjsutments **
+/- 2 pips for each extra checker on board
+ 2 pips for each extra checker on the ace point (more than 2)
+ 1 pip for each extra checker on the deuce point (more than 2)
+ 1/2 pip for each extra outside crossover
-1 pip for each additional occupied home board point

I wouldn't make any adjustments to this position, but would note that Lyurix has a better bearoff since I already have guys on my ace and his setup if more like the triangle.

So, 10% of 75 +1 is 9 pips.  Point of last take is 9 pips and I can double if I lead by six pips or more.  Double / Take.

Ballard Rule of 57.

This is just a more precise way to estimate Trice's last take for races of 57 pips or more.

Take Leader pipcount - 33, double it, and find the nearest square root.  This is point of last take.

75 - 33 = 44 X 2 = 88.  Sq rt of 88 is about 9.5.

So once again. Double / Take

Keith Count

Below image is from Phil Simborg, an excellent summary of the Keith Count method.

That said, I don't use it because I always get confused on applying the rules.

Leader: 75 + 2 = 77.  Add 1/7 or 11 = 88. 
Trailer: 83 (no adjustments). 

Therefore, No Double / Take per Keith (assuming I am doing it right - not sure)

EPC / Stick Method

Estimate EPC or effectice pip count for both sides.
EPC / 7 = # of Rolls to go
# of Rolls to go - 3 = Trailer's point of last take
Double withing 2 pip of Last Take
Redouble within 1 pip of Last take

I would have guessed wastage of 10 for me (which is wrong) or EPC of 75+10 or 85.
I would have guessed wastage of 7 for Lyurix (which is also wrong) or EPC of 83 + 7 or 90.

85 / 7 = 12, less 3 is 9.  So last take of 9 pips.
Lyurix can take with 85 + 9 = 94 pips
He has 90 which is more than 2 pips away from last take so No Double / Take using this method.

Again, not sure if I am applying this correctly.

Score is 5 away 5 away and Lyurix is on roll.  Cube action?

is Lyurix

score: 2
pip: 136
7 point match
                          pip: 153
score: 2

is Chutzpah
on roll, cube action?

Analyzed in XG Roller+ No double Double/Take
  Player Winning Chances: 71.88% (G:30.47% B:1.15%) 71.63% (G:31.60% B:1.09%)
  Opponent Winning Chances: 28.12% (G:6.05% B:0.26%) 28.37% (G:6.42% B:0.29%)
  Cubeless Equities +0.672 +1.475
Cubeful Equities
     No double:+0.920 (-0.080)
     Double/Take:+1.250 (+0.250)
xg Double/Pass:+1.000
Best Cube action: Double / Pass
eXtreme Gammon Version: 2.02, MET: Kazaross XG2
Lyurix doubled and I took. Oops, a double whopper with cheese. That will leave a mark.

Let's look at this a few different ways. 

First, what does PRAT suggest?

Position - I am outboarded 3 to 2 and have 2 men back to 1, with one in the air.  He has 10 men in the zone to attack with.  Large advantage Lyurix

Race - I am significantly down in the race.  Minus 17 pips and he is on roll and I am in the air.  Significant advantage Lyurix.

Threats - He has three builders working on the 5 point - I count 10 numbers that immediately make the 5 point next turn.  PLus again I have a man in the air.  Significant threats.

0 for 3 adds up to a clear drop. 

Besides this, Lyurix enjoys an elevated gammon value of .66 at this score - gammons are more valuable than for money.  This is extra incentive to drop, not that I needed any.

What do Stick's guidelines suggest?

Below are my notes from some early issues of Stick Daily Quiz Recaps - sadly these are being discontinued.

Stick Stat. Early game blitzes that are proper Double / take are about 65-68% wins and 25-28% gammon wins for the stronger side (Issue 1: DQ 4.1.11)

Caution!  Worst error in blitz is to underestimate gammon losses and take a monster pass.

Stick's Early blitz evaluation criteria: (Issue 2: DQ 4.8.11, Issue 4: DQ 4.22.11)
  • The race. I always like to note the race. It will be more important than some positions than others but it's a valuable detail to know and often plays a role in your decision.
  • How many checkers on the bar?  Big difference between no men up versus 1 man versus 2 men up.
  • Number of men in the zone. The key number that weighs in on the possible success of a blitz is 10 men in the zone.
    • If there are more than 10 men in the zone that's a lot of wood and you should be careful about taking any cubes.
    • If there are less than 10 men it's generally an easy take.
    • If there are exactly 10 take it on a position by position basis weighing in the other relevant factors.
  • Diversification of men in the zone. Clearly you'd rather have your men diversified than all stacked up on the same point.
  • Efficiency of men in the zone. Again, 10 is the magic number for minimum checkers you'd like to have in the zone but how they're put to work is important.
    • As a simple example in our position above we have 10 men in the zone in a standard looking blitz position.
    • Imagine if these 10 checkers instead made a prime from from the three point to the seven point. This would be light years better than the position we now have.
  • Status of the doubler's back checkers. If the checkers are split it's a big swing versus both of them still being on the 24 point. If one of them has already escaped it will make a big difference.
  • Additional points the person cubing has made. For each additional point the doubler has made, especailly inner board points, you have to be more and more careful if you're considering taking a cube.
    • A good rule of thumb is most (closer to all) positions where your opponent has a two point board or less are takes.
    • If he has a three point board or stronger beware. There are many exceptions to this statement of course but it's not a bad guideline.
  • Defender's offensive progress. Has the defender made any real progress on his side of the board? Any new points, esp. inner board points, will make his ability to counter punch while the attacker is trying to carry out the blitz more potent.
  • Other Tweak factors.
    • How “in the zone” are the 10 checkers? (the closer the better for the attacker)
    • What is likely to happen on the next exchange of rolls?
    • Match Score and gammon values.

So, looking at Stick's criteria - he has a 3 point board and 10 in the zone, which spells danger but not automatic drop.

Unfortunately the other factors are in Lyurix's favor:

  • I have an additional point, but it is the lame 2 point.  So this helps me some, but not too much.
  • Lyurix's 10 men in the zone are working well by aiming at the key 5 point.  As noted earlier, 10 rolls make the 5 point immediately.
  • Lyurix has already escaped one back man.  This is huge. 
  • Note Stick's stat that proper Double / take are about 65-68% wins and 25-28% gammon wins for the stronger side.  Here XG gives 72% wins and 30% Gammons - more than the guideline.  I guess we would have to infer this from the other factors.

In any case, this looks like a comfortable drop any way you look at.

I trail 3 away 1 away Post crawford and have 55 to play. 

is Lyurix

score: 6
pip: 159
7 point match
                          pip: 156
score: 4

is Chutzpah
to play 55

1.XG Roller+13/8(2) 6/1*(2) eq: +0.695
61.47% (G:21.48% B:0.46%)
38.53% (G:7.05% B:0.24%)
2.XG Roller+8/3(2) 6/1*(2) eq: +0.653 (-0.042)
58.79% (G:25.09% B:0.56%)
41.21% (G:8.27% B:0.37%)
3.2-ply13/3 8/3 6/1* eq: +0.539 (-0.156)
56.33% (G:19.24% B:0.61%)
43.67% (G:8.84% B:0.40%)
eXtreme Gammon Version: 2.02, MET: Kazaross XG2

I made the 'automatic' but incorrect play 8/3(2), 6/1*(2).

Better is 13/8(2), 6/1*(2).  This play strikes me as odd, but does crop up from time to time.  I don't fell I really understand what is going on.  Apparently you just don't want get hit so leaving a blot on the 8 point is simply wrong.

DMP.  51 to play.

is Lyurix

score: 6
pip: 125
7 point match
                          pip: 103
score: 6

is Chutzpah
to play 51

1.XG Roller+6/1 5/4eq: +0.544
77.21% (G:10.41% B:0.09%)
22.79% (G:2.65% B:0.09%)
2.XG Roller+14/13 14/9eq: +0.474 (-0.070)
73.70% (G:12.75% B:0.35%)
26.30% (G:5.91% B:0.25%)
3.4-ply14/8eq: +0.461 (-0.083)
73.06% (G:14.90% B:0.43%)
26.94% (G:3.88% B:0.11%)
eXtreme Gammon Version: 2.02, MET: Kazaross XG2

I elected to Pay now, moving 14/9, 14/13 and duplicating ones.  This was the wrong idea, and the better play was the ugly but safe 6/1, 5/4.

I guess the goal is simply to come home safe and win the game.  Therefore, safety is a premium and you don't want to leave a shot if you don't have to.  Here, the roll plays, sort of ugly, but it plays.  Next time, if I roll two bigs I can simply jump past his midpoint while if I roll an ace or a duece I can play safe once more and wait for a better roll to either clear or attack his blot.

Still DMP.  Next roll.  How to play 41?

is Lyurix

score: 6
pip: 117
7 point match
                          pip: 97
score: 6

is Chutzpah
to play 41

1.XG Roller+13/9 5/4eq: +0.694
84.72% (G:8.28% B:0.06%)
15.28% (G:0.86% B:0.02%)
2.XG Roller+13/9 4/3eq: +0.577 (-0.117)
78.87% (G:10.71% B:0.32%)
21.13% (G:4.68% B:0.28%)
3.4-ply13/8eq: +0.708 (+0.014)
85.41% (G:15.74% B:0.37%)
14.59% (G:0.92% B:0.02%)
eXtreme Gammon Version: 2.02, MET: Kazaross XG2
I completed the six prime with 13/9, and slotted the next point with 4/3.

Same theme as prior roll applies here.  My move looks sexy but takes chances for no reason.  Sure, most likely, Lyurix misses, or he hits and my prime holds up and I won anyway - but why take the chance when you don't need to?

Better was 13/9, also completing the full prime and then simply 5/4.  Sure, the builders are a bit ugly but who cares?  All I need to do is roll home safe and win the game.

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