BBD1 : Round 2 : Zsolt Tasnadi vs Liliane Baptista. High anchor games and a bear-off cube.

Liliane Baptista (left) vs Zsolt Tasnadi (right)

In backgammon, certain types of positions occur time and time again.  One of the most common types are holding games.  In a holding game, one player has made an advanced anchor (4-point or higher) and the opponent has escaped his men to the midpoint.  Now it is time for the favorite to assess all features of the position and decide on his cube action.

In their match, Zsolt and Liliane each got doubled in a 4-point holding game and struggled with the cube decision.  Here, for instance, is the position in Game 1 :

White (Zsolt) on roll.
Can he double? Can Red (Lilane) take?

First thing to consider is – as always –  the RACE.  Zsolt is only up 11 pips.  Typically, against a 4-point anchor you would need about 20 pips race advantage to have a correct double.  Of course, with his barpoint already made,  Zsolt has a broken 5-prime which compensates for the fact that he has not yet fully safetied his last checker to the midpoint.  Also, Liliane’s own forward position is far from perfect : she has not yet made a extra point in her board, but she should have no problems building a strong board soon.  Moreover, in such kinds of positions the volatility is generally low.  This means that only rolls like 66, 55 and 44 would lose Zsolt’s  market.  Therefore it is very improbable that Zsolt would make a big error by waiting one roll before cubing.

Player Winning Chances: 73,72% (G:2,76% B:0,05%)
Opponent Winning Chances: 26,28% (G:1,24% B:0,01%)

No double: +0,799 (-0,009)
Double/Take: +0,807
Double/Pass: +1,000 (+0,193)

Best Cube action: Double / Take

As eXtreme Gammon shows, this is a borderline Double, but an easy Take for the defender.  Liliane does not take a big risk in taking this.  She can only lose one extra point by taking, since the chance that she will get gammoned is less than 3%.  However, players who are not familiar with these positions might easily get spooked and give away a point.  This is what happened in the match.  Liliane passed, making a big mistake in doing so.

Knowing your opponent’s tendencies can help with the cube action here.  Maybe Zsolt estimated that there was a significant chance that Liliane would pass.  In that case, his double becomes a strong bluff double.  If he did not consider Liliane’s weakness, his double could be called premature.

In Game 2, the roles were reversed.  This time Zsolt is the one defending from the 4-point anchor :

Red (Liliane) on roll.
Can she double? Can White (Zsolt) take?

Here, Liliane is up 26 pips in the RACE.  She could have turned the cube 2 rolls earlier, but decided to wait.  This turned out well for her, because Zsolt, probably thinking the open 5-point was a significant weakness in Red’s position, took the cube without thinking too long about it.  This also turns out to be a big mistake :

Player Winning Chances: 81,58% (G:2,79% B:0,02%)
Opponent Winning Chances: 18,42% (G:0,90% B:0,04%)

No double: +0,988 (-0,012)
Double/Take: +1,202 (+0,202)
Double/Pass: +1,000

Best Cube action: Double / Pass

The Americans have come up with the term double whopper for errors of this magnitude.  By accepting this cube, Zsolt sacrificed 0,202 mps in equity.

Something to consider when you get doubled is whether the opponent will be prone to making checker play mistakes in the game continuation.  In the position above, Red has a relatively easy task bringing the checkers home.  Still, she might not dare leave an indirect shot in clearing the 11-point or misplace her checkers in some other way.  Still, these errors are unlikely to be big mistakes, so they would not compensate for the 0,202 in sacrificed equity.

However, this is what happened 2 rolls later :

The reader can have no doubt as to what is the correct move : making the 5-point is hugely correct.  I am sure Liliane will play this correctly 90% of the times, but due to the tension of the big occasion, she nervously played 8/6 8/2.  Her underlying thought may have been that a point cleared, is a point not to be feared, and there are situations where this would definitely be the right play.  Here, however, this useful tenet does not apply.

1. XG Roller++ 11/5 7/5 eq:+0,661
Player: 84,29% (G:2,56% B:0,04%)
Opponent: 15,71% (G:0,61% B:0,01%)

2. XG Roller++ 8/6 8/2 eq:+0,484 (-0,177)
Player: 76,71% (G:2,59% B:0,05%)
Opponent: 23,29% (G:1,30% B:0,02%)

To make matters worse for Liliane, Zsolt ended up escaping with a 66 and reached this position some rolls later :

White (Zsolt) on roll.
Can he double? Can Red (Liliane) take?

This is a classic bear-off cube decision.  If Zsolt rolls an ace, he loses, in all other cases he wins.  This is typically something that distinguishes Intermediate players from Beginners : the ability to calculate probabilities.  What are the chances Zsolt rolls an ace? Well, it is 11/36 or 30%.  That means he is 70% favorite here and should redouble.  Liliane, who has 30% winning chances, should take.  It must be said that it might be scary for the better player to give this cube, because rolling an ace swings the score to 1-4 down in a match to 7.  However, the error in not cubing is so big (0,415 – !), that the skill difference between both players would have to be between 12 and 15 PR ( = difference in Performance Rating as calculated by eXtree Gammon) for not doubling to be correct.  This means that a world class player, who averages about 4 PR, would make an error cubing this against Liliane.  Zsolt, who played this match at Advanced level, had to bite the bullet and ship the cube.  He took a long time fretting over it, but eventually redoubled to 4.  Liliane, to her credit, accepted, which as a matter of fact is very well played.  Many players, even strong ones, get overwhelmed by superstitions and end up passing this.  Gutsy cube action by both players!

Zsolt did not roll a 1, took a 5-0 (7) lead, and ended up beating Liliane 7-0.

Hopefully, these remarks will motivate players of all levels to spend some time studying the game.  Improving your game gives greater long-term satisfaction than winning the occasional match by chance.

See you soon.

M