Feature Columnists: Douglas Zare - The Zare Formula

Backgammon Questions (Part 1)

13 Apr 2015 - by Douglas Zare

For 13 years, this has been a monthly column on the mathematics of backgammon. When GammonVillage first asked me to write this column, I was worried about running out of things to say, and I wrote down a year's worth of column ideas before I agreed.


Rating:  4.57
"The Zare Formula" Archive
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One Extra Point

04 Mar 2015 - by Douglas Zare

One of the most important features of a contact backgammon position is board strength. While the qualities of the boards matter, it is easy to classify positions by the numbers of home board points.

Rating:  3.57

Stack and Straggler

02 Feb 2015 - by Douglas Zare

Backgammon games are often concluded by contact bearoffs. We often have a checker sent back in the bearoff, and need to evaluate a race with one checker coming home. If the checkers in your home board are on the ace point, this is a classic stack-and-straggler position.

Rating:  4.00

Two Children and the Tuesday Birthday Problem

09 Jan 2015 - by Douglas Zare

Backgammon players have a lot of practice working with objective probabilities and risks. These are things many people find counterintuitive. In many cases, backgammon players may be better able to avoid probability fallacies and errors. Let's look at a probability puzzle where many people have trouble, but where backgammon players might have an advantage.

Rating:  5.00

Roll Variance in the Bearoff - Part 3

03 Dec 2014 - by Douglas Zare

In this column, we will look at estimating the roll variance of actual backgammon positions. When we want to estimate the effective pip count, there are two easy cases.

Rating:  5.00

Expected Utility

04 Nov 2014 - by Douglas Zare

When I started to play backgammon seriously, my intuition about probabilities became much better, and I think this is a common experience for backgammon players.

Rating:  5.00

Roll Variance in the Bearoff - Part 2

08 Oct 2014 - by Douglas Zare

In Part 1, we found that roll variance is a useful addition to the effective pip count for analyzing backgammon races. Let's do the same kind of analysis for other positions with about the same effective pip count of 52, but different roll variances for the leader.

Rating:  4.75

Roll Variance in the Bearoff - Part 1

03 Sep 2014 - by Douglas Zare

The effective pip count is a great way to analyze backgammon races. Although people continue to work on alternatives, many of these are more complicated but less accurate than learning to estimate the effective pip count.

Rating:  4.57

Variations on a Single Reference Position

05 Aug 2014 - by Douglas Zare

A backgammon reference position can mean a position whose value is known, but it should mean a situation you understand. You are unlikely to repeat an exact contact position after the opening.

Rating:  4.88

Crashed Anchor Games

02 Jul 2014 - by Douglas Zare

In backgammon matches, we need to be able to evaluate positions which are clear passes for money play. One such type of position is a crashed deep anchor game where we have 2 or more checkers stacked up behind a prime while our forward position has crunched.

Rating:  4.83

Backgammon Game Theory

02 Jun 2014 - by Douglas Zare

This column is about the mathematical theory of backgammon, but we have hardly seen anything about the part of mathematics (and economics) called game theory. The reason is that game theory says almost nothing directly about backgammon.

Rating:  4.50

Better than Average

05 May 2014 - by Douglas Zare

We would like to estimate many quantities in backgammon. What is the value of this position if I take? What is my chance to win against player X? What is my error rate?

Rating:  4.33

Clearing the 11 Point

01 Apr 2014 - by Douglas Zare

One of the simplest families of backgammon reference positions is the high anchor holding game. If you have a racing lead of 20 or more pips, you are trying to clear the midpoint against an anchor on the 5 point or bar point, then the position is usually a double and a take.

Rating:  4.86

Backgammon Records

03 Mar 2014 - by Douglas Zare

Some backgammon events are extreme. You might have your largest box run ever, make the largest blunder, get the luckiest exchange, play the longest game, or face your strongest opponent. We'll call it a record if it was the best/worst event ever at the time it occurred, even if it was surpassed later.

Rating:  4.50

Rolling the Doubling Cube

01 Feb 2014 - by Douglas Zare

Backgammon stands out from other games of skill and chance because of the doubling cube. In fact, the doubling cube could be added to many other activities, even spectator sports. However, many casual players don't know how the doubling cube is used.

Rating:  4.00

Accounting for Opponent Errors

09 Jan 2014 - by Douglas Zare

Many people pretend backgammon is solitaire. We focus on playing with a low error rate, and a side-effect is doing well against our opponents. It is possible to do better than this by recognizing that some plays make your opponent's decisions harder.

Rating:  5.00

Lasting Longer

13 Nov 2013 - by Douglas Zare

At the end of my October column, I asked about last-longer bets in single-elimination backgammon tournaments, where two players bet on which of them will go farther. Unlike most situations in backgammon, this allows the possibility of a tie if both players are knocked out in the same round.

Rating:  4.60

Backgammon Odds and Ends

04 Oct 2013 - by Douglas Zare

Here are two topics in the theory of backgammon which are not deep enough for their own articles: After the Pass and Duplicate Props.

Rating:  5.00

Asymmetric Matches

04 Sep 2013 - by Douglas Zare

If you want to become a strong backgammon player, it is enough to learn which plays are right against strong opponents. Usually those same plays are optimal against any opponents. However, if you want to maximize your chances to win tournaments, you have to make the "wrong" plays at times.

Rating:  4.60

Rolling Coins

02 Aug 2013 - by Douglas Zare

Suppose you are ready to play backgammon, but your dice are missing. You do have a coin. Can you use a sequence of coin tosses as a substitute for the dice?

Rating:  4.00

Pure Rolls in Match Play

01 Jul 2013 - by Douglas Zare

Bearoffs in which there are no misses, and each side saves a roll with any double, are among the simplest backgammon positions. There are no checker play decisions, only cube decisions.

Rating:  3.60

Irrelevant Alternatives

01 May 2013 - by Douglas Zare

Classical economics describes backgammon bots much better than it describes how people make decisions. In classical economics, agents consider all possibilities, and choose the option with the highest evaluation. That's very similar to the way backgammon bots choose plays.

Rating:  4.25

Computer Go

01 Apr 2013 - by Douglas Zare

Since the late 1980s or early 1990s, computers have been strong in backgammon and chess, far better than most competitive people. At that time, computer go programs were extremely weak, and could be beaten by typical club players.

Rating:  5.00

Game, Set, and Match

01 Mar 2013 - by Douglas Zare

Most backgammon tournament rounds are single matches. Some use the best of three matches to determine the result. What is a better way to test backgammon skill, playing a best of three 11 point matches, or one longer match, say to 25 points?

Rating:  4.78

The Doubling Point

01 Feb 2013 - by Douglas Zare

The doubling point is a basic concept for understanding backgammon match play. The doubling point can be calculated from the match equity table rather than from any one position, but it can help us to analyze particular cube decisions over the board.

Rating:  4.25

Taking Count

04 Jan 2013 - by Douglas Zare

A fundamental difference between backgammon bots and people is that people try to find the right play, while bots try to evaluate each position. We look at a position and find criteria for safe play versus bold play, for example, while bots simply evaluate each possible result of making a move.

Rating:  4.83

Speed Boards

01 Dec 2012 - by Douglas Zare

Backgammon races are generally simple, and what could be simpler than a checker play decision with a speed board? And yet, I ran across a tough decision recently with a choice between two speed boards. I hope you will find it interesting, too.

Rating:  5.00

Bot-Breaking Backgammon Positions

01 Nov 2012 - by Douglas Zare

When a backgammon bot disagrees with a human, it's usually right to bet that the bot is correct. However, there are many backgammon positions the bots don't understand well, including quite simple ones.

Rating:  5.00

Model Backgammon Matches, Part 1

01 Oct 2012 - by Douglas Zare

Backgammon match play is complicated. Even after we learn that the points have different values, the interactions between the doubling cube and match scores are not obvious.

Rating:  4.50

Sixteen Checkers

11 Sep 2012 - by Douglas Zare

Any experienced backgammon player knows it is bad to have three checkers pinned back on your opponent's ace point. In the opening, it's usually right to move that third checker off the ace point as soon as you can without wasting a perfecta. However, do we know why that configuration is bad?

Rating:  4.63

Extreme Bearoffs

03 Jul 2012 - by Douglas Zare

Some of the first backgammon neural nets were trained to play properly in bearoff races. They were utter failures! It turns out to be surprisingly difficult to train a neural net to understand the bearoff as well as people do.

Rating:  4.63

Gammon Price When Too Good

01 Jun 2012 - by Douglas Zare

One frontier of backgammon theory is the study of positions which are too good to double. Most of the time, we study positions between the take points, but it is still important to play well when we are too good to double.

Rating:  5.00

Model Backgammon and the Jacoby Rule

15 May 2012 - by Douglas Zare

Since backgammon bots play quite well, it is easy to assume that the theory of backgammon is almost complete. In fact, there are many fundamental questions which are still not settled. While the bots help, they are often not the most convenient tool.

Rating:  5.00

Zare Race Database

01 Apr 2012 - by Douglas Zare

There are many backgammon race databases. I'm going to add another to the collection, the Zare Race Database. I wrote some of the tools to create the database years ago, but I only recently wrote an interface which allows easier access to the information.

Rating:  5.00

Bearing In - Part 1

01 Mar 2012 - by Douglas Zare

Over the years, I have criticised many backgammon racing formulas for being too complicated for their level of accuracy. Last month we saw an example, Merrigan's Metric Formula.

Rating:  4.75

Merrigan's Metric Formula

01 Feb 2012 - by Douglas Zare

Nigel Merrigan wrote an article on backgammon races, which discusses some work on racing theory. The main addition is a formula for estimating the probability of winning a long race, called the Metric formula.

Rating:  4.83

Gammon Races - Part 2

14 Dec 2011 - by Douglas Zare

Races are the simplest part of backgammon, but they still produce interesting checker plays. Let us continue to study racing to save the gammon. In this column we will use a database to find the optimal plays.

Rating:  4.67

Gammon Races - Part 1

07 Nov 2011 - by Douglas Zare

Even the last few rolls of a backgammon race can have some interesting checker play decisions. In this column we will look at some of the decisions about filling gaps in your board and the effective pip count.

Rating:  4.80

Two Checker Races

03 Oct 2011 - by Douglas Zare

Backgammon is too complicated to solve in the near future, but pieces of the game can be analyzed completely. If you have two checkers to race home, you have a few decisions. What should you try to accomplish?

Rating:  4.40

Final Contact

01 Sep 2011 - by Douglas Zare

We understand backgammon races pretty well using tools such as the pip count and effective pip count. What about contact positions where each side has only one checker in play?

Rating:  4.86


01 Aug 2011 - by Douglas Zare

In a past column, we looked at streaks in backgammon such as rolling doubles 5 times in a row. It is also interesting to look at clumps, or clusters of events. For example, in a recent game, I rolled 10 doubles in 24 rolls.

Rating:  4.00

Winning Causes Poor Play

01 Jun 2011 - by Douglas Zare

Backgammon is a game of skill and luck, so there are times you will win even if your opponent outplayed you. You will also lose some matches against players who are playing poorly but rolling well.

Rating:  4.63

The Backgammon Pentathlon

03 May 2011 - by Douglas Zare

Backgammon match play is like a pentathlon from track and field. An athlete training for a pentathlon usually concentrates on one of the five events at a time, perhaps running one time, and then throwing a javelin another.

Rating:  3.86

Post-Crawford Redoubles

01 Apr 2011 - by Douglas Zare

A lot of match equity is at stake in each game after the Crawford game, and also on large cubes, but the backgammon literature says little about the intersection of these situations. This column fills that appropriate gap.

Rating:  3.78

Mismeasuring Luck

02 Mar 2011 - by Douglas Zare

Backgammon programs offer many statistics after analyzing a match. This feedback is valuable, but at times it is confusing since the statistics are complicated. In fact, some values reported by the bots have almost no meaning.

Rating:  3.67

Dangerous Redoubles

03 Feb 2011 - by Douglas Zare

Backgammon match play is tricky since the points do not have the same value. It gets particularly interesting when the doubling cube is on 2 or higher, and those decisions are often very far from decisions in a money session.

Rating:  4.78

Across the Scores

04 Jan 2011 - by Douglas Zare

When we play backgammon matches, we face a series of decisions at one match score, and then move on to the next score. It is an enlightening exercise to do the reverse.

Rating:  4.50

Repeated Shots

02 Dec 2010 - by Douglas Zare

Backgammon involves weighing risks against each other. As humans, we don't have to decide how much each position is worth, only which play is best.

Rating:  4.82

After Closing Out The Last Checker, Part 3

03 Nov 2010 - by Douglas Zare

We continue our study of backgammon after closing out the last checker. In this column, we will look at the races and contact positions which arise after the last checker enters, although this will have consequences even for the early bearoff.

Rating:  4.91

After Closing Out The Last Checker, Part 2

04 Oct 2010 - by Douglas Zare

We continue our study of backgammon after closing out the last checker. In Part 1, we looked at the early bearoff. In Part 2, we will concentrate on positions where the last checker is still on the bar.

Rating:  4.50

After Closing Out The Last Checker, Part 1

02 Sep 2010 - by Douglas Zare

One backgammon milestone I have yet to accomplish is winning in real play after closing out my opponent's 15th checker. My style of play does not lead to as many backgames and desperate ace point games which lead to hitting the last checker.

Rating:  4.67

One Tenth of a Point

03 Aug 2010 - by Douglas Zare

Backgammon positions which are known to be close take/pass decisions are commonly studied. Knowing which positions are on the boundary can help you to make the right decision.

Rating:  4.75

Small Changes

01 Jul 2010 - by Douglas Zare

What good does studying a single backgammon position do? Except for a few positions in the opening or endgame, or in a proposition, you are unlikely to hit that exact position again.

Rating:  4.18

Monty Hall

07 Jun 2010 - by Douglas Zare

Probability is important in backgammon. We make decisions under risk, and we have to interpret noisy evidence, such as playing out a position a single time when it would take a rollout with thousands of trials to be conclusive.

Rating:  4.56

Drilling Down

01 May 2010 - by Douglas Zare

A key idea in backgammon is equity, the average value of a position assuming perfect play. This is a weighted average over all of the possible sequences of rolls, giving the sequences appropriate weights assuming the dice are fair.

Rating:  4.14

Subtle Bias

01 Apr 2010 - by Douglas Zare

If the dice are fair, then when you look back over your records, you should find that 1/6 of the dice are 6s, right? What else could be meant by fair dice? However, by the end of the column, I hope it won't be so obvious.

Rating:  4.00

Rolling Dice Over The Phone

01 Mar 2010 - by Douglas Zare

Usually, when people play backgammon online, it is on a server which generates the dice. Despite the complaints about every single server, people trust the servers' dice. How can you tell if a server's dice are fair?

Rating:  4.50

Desperate Races

01 Feb 2010 - by Douglas Zare

In this column, we'll see a simple, computable racing formula due to Danny Kleinman. We'll use it to analyze a backgammon checker play decision which depends on correctly evaluating two desperate races.

Rating:  4.19

Troubled Assets in Backgammon

01 Jan 2010 - by Douglas Zare

What can backgammon players learn from the financial crisis of 2008-2009? The same mental errors which led to the failures of so many banks and companies show up in chouettes and your private struggle against the bots.

Rating:  4.53

Backgammon Corrections

01 Dec 2009 - by Douglas Zare

Backgammon programs are good at saying what the right play is, but they aren't good at explaining why. In this column, we'll look at some exercises for using bot feedback to understand why a decision is right so you can play better.

Rating:  4.24

The Long Run

02 Nov 2009 - by Douglas Zare

In the short run, a game of skill and chance like backgammon might be viewed as a game of chess for $1 plus a coin flip for $10. In the long run it might be described as a game of chess for $1000 plus a coin flip for $100.

Rating:  4.45

Duplication In Backgammon

01 Oct 2009 - by Douglas Zare

Duplication is one of the most fundamental tactical ideas in backgammon. Understanding the basics of duplication might separate the intermediate player from the novice, but there are aspects of duplication worth studying by experts.

Rating:  4.62

Walter Trice

24 Aug 2009 - by Douglas Zare

Walter Trice just passed away. I'm still reeling from the news. He was my friend and collaborator, a role model, and an advisor.

Rating:  4.00

Odd Match Rules

01 Aug 2009 - by Douglas Zare

The international standard for backgammon matches is that they use the doubling cube with the Crawford Rule. However, you can occasionally find matches played without the doubling cube, or without the Crawford rule.

Rating:  4.70

Beyond The Obvious

01 Jul 2009 - by Douglas Zare

Douglas Zare's encounter with the largest EMG checker play blunder he's ever seen reminds him of some advanced plays involving casual players in live backgammon clubs.

Rating:  4.00

Gnu Backgammon vs. Snowie Openings, Part 3

01 Jun 2009 - by Douglas Zare

This is the third and final part of our survey of responses to opening rolls according to Gnu Backgammon and Snowie, judged by long rollouts.

Rating:  4.82

Gnu Backgammon vs. Snowie Openings, Part 2

01 May 2009 - by Douglas Zare

Gnu Backgammon and Snowie are both very strong, but in about 15% of responses to the opening roll, they disagree with each other, or with rollouts. Let's continue our survey, using long Gnu Backgammon rollouts as the referee.

Rating:  4.92

Gnu Backgammon vs. Snowie Openings, Part 1

01 Apr 2009 - by Douglas Zare

Gnu Backgammon and Snowie are both extremely strong backgammon players. Some types of positions are better understood by one bot than the other. Which bot understands the opening better?

Rating:  4.64

Bot Insanity

01 Mar 2009 - by Douglas Zare

Backgammon bots are usually great at judging plays, but occasionally they favor an insane play which no human player would seriously prefer. Rollouts often seem to confirm the insane play.

Rating:  4.59

New Backgammon Positions

01 Feb 2009 - by Douglas Zare

Backgammon remains exciting to experienced players and comprehensible to beginners because most games have both easy and tough decisions. A few decisions per game are difficult even for experts, whether we realize they are difficult or not.

Rating:  4.00

Backgammon Timing

01 Jan 2009 - by Douglas Zare

Timing may be the most difficult of the important backgammon concepts to express in words. Timing in backgammon refers to whether you can maintain your assets long enough to use them.

Rating:  4.33

Stack and Stragglers

01 Dec 2008 - by Douglas Zare

The effective pip count is particularly useful for understanding inefficient backgammon races. In this column, we will look at two epc formulas found by Walter Trice, for 0 or 1 straggler, and we will extend them to the case of 2 stragglers.

Rating:  4.71

Wrong Match Equity Table

01 Nov 2008 - by Douglas Zare

Using any reasonable match equity table is better than not using anything, but now there are multiple tables in use. Woolsey has a commonly used MET, but Snowie uses its own MET, and GNU uses a different table by default. What happens when the tables conflict?

Rating:  4.79

Gaps and Wastage

01 Oct 2008 - by Douglas Zare

When a backgammon game becomes an even race, you should aim for the 753 position, with 7 checkers on the 6 point, 5 on the 5 point, and 3 on the 4 point. In practice, we rarely achieve it. What should you do?

Rating:  4.31

Backgammon's Virtual End Zone

01 Aug 2008 - by Douglas Zare

Backgammon's doubling cube means you don't have to bear off all of your checkers to win. The virtual end zone tells you the game winning chances you need to plan to reach to win the game with the doubling cube.

Rating:  3.60

Lessons From Backgammon

01 Jul 2008 - by Douglas Zare

Some of the things we learn from studying backgammon give us an advantage elsewhere. Strong backgammon players have succeeded in many areas, from other games such as poker, to the financial markets.

Rating:  4.73

Backgammon Experience

01 Jun 2008 - by Douglas Zare

In this column, we will look at the theory of deciding between plays based on experience. This may help to see where our backgammon-playing experience is insufficient, and needs the most help from other learning methods.

Rating:  4.38

Final Contact in Backgammon Games

01 May 2008 - by Douglas Zare

In backgammon, when 94% of your opponent's checkers get by you, you can still have a commanding advantage, or decent winning chances even with only one obstacle in front of your opponent's last straggler.

Rating:  4.50

Initiative in Backgammon

01 Apr 2008 - by Douglas Zare

The initiative of a backgammon position is the equity of the position when you are on roll minus the equity when your opponent is on roll. Studying the initiative is an exercise for understanding backgammon positions better.

Rating:  3.77

Cube Vigorish in Backgammon Match Play

01 Mar 2008 - by Douglas Zare

In a past column, we quantified the value from using the doubling cube, and applied that to understanding some take/pass decisions in money play. In this column, we'll continue to look at cube vigorish, but the application will be to a checker play decision in a backgammon match.

Rating:  4.71


01 Feb 2008 - by Douglas Zare

Luck is an essential part of backgammon. Some players go to great lengths to tell you how unlucky they are and how lucky you are. In this column, we'll look at an exercise I use which has the side effect of being able to trap some of the excessive complainers in live games.

Rating:  4.17

Pips, Crossovers, and Stacks

01 Jan 2008 - by Douglas Zare

Avoiding gammons and backgammons is not flashy, but proper technique in grim situations is part of playing well. At the end of the session, points gained from winning extra gammons are just as valuable as points saved from losing fewer gammons.

Rating:  4.63

Backgammon Grand Prix

01 Dec 2007 - by Douglas Zare

Many backgammon clubs have a Grand Prix-style points race each year. Players receive points for placing well in the club's tournaments, and can never lose points. If you want to reward playing well, why award any points to second place?

Rating:  3.50

Game Integrity, Part 1

01 Nov 2007 - by Douglas Zare

I've been planning to write about testing claims of cheating and unfair dice in backgammon. While I will discuss some of the foundations needed to analyze these claims fairly, this column is about the current cheating scandal involving Absolute Poker, one of the largest online poker sites.

Rating:  4.59

Backgammon Error Rates By Move Number

01 Oct 2007 - by Douglas Zare

Where are the most serious backgammon errors committed? Are the most damaging errors well-practiced mistakes in the opening, misjudgments in the middle game, or poor technique in the endgame?

Rating:  4.20

Serious Backgammon Errors - Late Loose Hits

01 Sep 2007 - by Douglas Zare

The most serious errors in backgammon are not necessarily the largest. Just as more equity is given up on checker play errors than cube blunders, common errors may contribute more to your error rate than blunders in rare positions.

Rating:  4.67

Could Backgammon Be Solved?

01 Aug 2007 - by Douglas Zare

In my June 2007 column, "The Essence of Backgammon," I remarked that the game of checkers is too complicated to be completely solved at present. Researchers at the University of Alberta recently announced a partial solution.

Rating:  5.00

Truncation Depth

01 Jul 2007 - by Douglas Zare

Backgammon bot evaluations are useful, but rollouts more reliably estimate the true value of the position. A rollout may be untruncated (full) or truncated. What is the difference to us? Why would we prefer one type of rollout over another?

Rating:  3.78

The Essence of Backgammon

01 Jun 2007 - by Douglas Zare

What distinguishes backgammon from chess, go, bridge, and poker? Which skills are emphasized most in backgammon? Backgammon shares many features with other games, but it doesn't emphasize them in the same proportion. Instead of diving into positions and technical details this month, let's take a step back and consider how backgammon compares with other games in several categories.

Rating:  4.78

Deconvolution and Ratings

07 May 2007 - by Douglas Zare

Deconvolution is a useful process in advanced mathematics. Convolution is blurring. Deconvolution is an attempt to recover the original sharp image or information. In this column, we'll look at natural deconvolution problems which occur in backgammon.

Rating:  3.86

Probability of Hitting

01 Apr 2007 - by Douglas Zare

In a holding game, your wins come from a combination of racing and hitting. How can we estimate the probability of hitting?

Rating:  5.00

Bot Bias

01 Mar 2007 - by Douglas Zare

Douglas Zare investigates the bias of backgammon bots, both of bots toward themselves, and of bots toward other bots. Along the way, he shows that bots disagree with each other more often and are farther from perfect play than you might expect.

Rating:  4.80

Rollout Confidence

01 Feb 2007 - by Douglas Zare

Before the dawn of backgammon bots, backgammon players would roll out positions by hand. Now, sophisticated backgammon bots do the rollouts automatically. But how do we know whether the bot is playing well in the rest of the game?

Rating:  3.80

Unbiased Nonsense

01 Jan 2007 - by Douglas Zare

Douglas Zare's latest article illustrates that objective numerical feedback is helpful, in backgammon and elsewhere in life. However, sometimes the feedback doesn't seem to make sense.

Rating:  4.00

Coming From Behind

01 Dec 2006 - by Douglas Zare

Luck and skill are not opposites. That backgammon involves luck means that whether you have the advantage or not, your plays still matter. If you have fallen behind or blundered several times, your next play can affect the probability with which you win.

Rating:  4.33

Error Rate Conversions

01 Nov 2006 - by Douglas Zare

There are several ways to quantify a skill advantage in backgammon, like error rates, ELO and expected points per game. There is no simple conversion between these measures, but in this column, we'll find some connections.

Rating:  4.83

Blocking Power

01 Oct 2006 - by Douglas Zare

In this column, we will introduce a numerical measure of the strength of a prime, blocking power. This is the number of pips you are forced to play elsewhere, not rolls. Like the effective pip count, or the probability of hitting a shot, blocking power must be combined with other considerations.

Rating:  5.00

Counting Wins

01 Sep 2006 - by Douglas Zare

Counting wins is a simple but powerful technique for approaching some tactical take/pass decisions, those likely to simplify quickly into positions that are easier to evaluate.

Rating:  4.29

Hustling for Casual Players

01 Aug 2006 - by Douglas Zare

Some serious observations about playing for money on a site with an Elo rating system can be applied by backgammon players below the expert level. You don't have to be a world-class player to win money playing backgammon.

Rating:  4.00

Normalizing Errors

01 Jul 2006 - by Douglas Zare

How do we measure the size of an error? How do we determine which errors are the most serious, and most worthy of attention? Two possibilities are to use match winning chances (mwc) and the money game equivalent (EMG). We'll see that neither is ideal, and that other normalizations are possible.

Rating:  4.67

Error Distribution

01 Jun 2006 - by Douglas Zare

When I make a really bad play, I study the position carefully until I understand the conceptual mistake I made. Afterwards, I sometimes get nightmares about my mistake.

Rating:  4.00

Gammons After Closeouts

01 May 2006 - by Douglas Zare

In Hoyle's 1745 work, "A Short Treatise On the Game of Back-Gammon," he covered many topics relevant to modern backgammon. In Chapter 7, he asked how likely it is to win a gammon after closing out one checker, when your opponent has 6 checkers to bring in plus the checker on the bar. His answer was that you win about 50% gammons.

Rating:  4.75

New Math

01 Apr 2006 - by Douglas Zare

Archaeologists have told me about the old New Math. At some point in the last millennium, mathematicians tried to introduce layers of abstraction so that children could distinguish between the number 3 and a set containing 3.

Rating:  4.89

Late Bearoff EPCs

01 Mar 2006 - by Douglas Zare

In this column, we'll look at the effective pip count of late bearoff positions - shorter than a 4-roll position. These are not hard to estimate with a little practice.

Rating:  4.67

Volatile Doubles

31 Jan 2006 - by Douglas Zare

In this column we'll look at potential doubles and redoubles in volatile positions where hitting is close to gin and missing usually leaves a race.

Rating:  4.33


01 Jan 2006 - by Douglas Zare

Most features of rarely encountered Crawford and post-Crawford match scores can be understood by interpolating between a few common scores. We find that they are similar to each other and most decisions do not become increasingly extreme.

Rating:  4.88

'33% Speed'

01 Dec 2005 - by Douglas Zare

'33% Speed' is a fast approximation to a normal 3-ply evaluation. Instead of averaging over all 441 dice sequences, the bot uses a balanced collection of 1/3 of the sequences and it is quite accurate for races and priming positions.

Rating:  4.75

Linearity In Backgammon

01 Nov 2005 - by Douglas Zare

In a mathematical approach to backgammon, we often want to convert one set of numbers to another and there are ways to construct accurate and simple mathematical models for these.

Rating:  4.40

Chouette Dynamics

01 Oct 2005 - by Douglas Zare

Chouettes add fun and complication to the game of backgammon. If you simply make the best play at each oppportunity, you will do well, but there is room for improvement.

Rating:  4.67

Uneven Matches

01 Sep 2005 - by Douglas Zare

At which match scores is the take point the most sensitive to the skill difference? We will study this question, and will find some answers that may be counterintuitive to most competitive players.

Rating:  4.50

The Cost Of A Shot

01 Aug 2005 - by Douglas Zare

It is not hard to count shots. The goal is to weigh the total cost of getting hit against the benefits when not hit. Let's consider the numerical cost of getting hit in a few situations and show numerical analysis done with the help of a bot.

Rating:  4.20

Inefficient Races

01 Jul 2005 - by Douglas Zare

Simple racing formulas tell us the take point for efficient races, where neither side has buried checkers. In this column, we will find simple, important adjustments to the racing formulas to use in inefficient races.

Rating:  4.13

Counting Positions

01 Jun 2005 - by Douglas Zare

Is backgammon solvable by a database? If the entire game is too complicated, which aspects of the game can be solved by databases? To try to answer these questions, we need to count positions, and look at the storage capabilities of computers.

Rating:  4.00

Timing Deep Anchor Games

01 May 2005 - by Douglas Zare

Deep anchor games hit many shots in the bearoff. They also get gammoned a lot. The relative frequencies of these depend on many factors, but one of the most important is the race.

Rating:  4.14

Running Gammons

01 Apr 2005 - by Douglas Zare

The effective pip count can be useful for analyzing races to save the gammon. In holding games, running gammons start to be significant with a 60 pip lead, and a 77 pip lead may make the race for the gammon close.

Rating:  4.43

Second Best

01 Mar 2005 - by Douglas Zare

Good numerical feedback from bots makes it is easier to improve if you focus on numbers you can control in the short run rather than trying to affect the outcome of the game.

Rating:  4.70

Closeouts And The EPC

01 Feb 2005 - by Douglas Zare

While we consider the effective pip count for races, particularly in the bearoff, it can also be useful in contact positions that often result in races.

Rating:  4.86

Deep Anchors

01 Jan 2005 - by Douglas Zare

Deep anchors generate many shots. In this column, we will take a quick survey of deep anchor games. We will look at how frequently they hit, how valuable those hits are, and the cost of keeping a deep anchor in backgammons.

Rating:  3.67


01 Dec 2004 - by Douglas Zare

Let us consider some common positions with only two ways to win: win the race and hit a shot. The two are easy to analyze separately, and the pieces can be combined to give an estimate of the winning chances over the board.

Rating:  4.25

One Last Point

01 Nov 2004 - by Douglas Zare

High-anchor holding games are common, so it is important to understand them. Let's consider one possible phase of a high-anchor holding game that can help us to make accurate plays game after game.

Rating:  5.00

The Price Of A Proposition

01 Oct 2004 - by Douglas Zare

Propositions arise when players disagree about the value of a position. Props are educational. Rollout results don't tell you how to play a position. You learn a lot by playing it out many times and it helps in decisions you'll face later.

Rating:  4.80


01 Sep 2004 - by Douglas Zare

A freezeout is when two players bring money to a table and then play according to table stakes until one player wins all the money. Though more common in poker, here are some theoretical issues related to freezeouts in backgammon.

Rating:  5.00

Undefined Equity - Part 2

01 Aug 2004 - by Douglas Zare

The mathematical model of backgammon breaks down in interesting ways. In this column, we'll see what happens if you play out the Paradox Position many times. We'll also look at match play and table stakes.

Rating:  5.00

Undefined Equity - Part 1

02 Jul 2004 - by Douglas Zare

The doubling cube may escalate so rapidly that the theoretical average value of a position (equity) may not be defined. Backgammon is the only 2-player zero-sum game allowing this possibility.

Rating:  4.67

Square Match Length

01 Jun 2004 - by Douglas Zare

Some 1-point matches turn into a race quickly. Others are exciting protracted battles that produce decision after decision. Is there an objective way to distinguish straightforward matches from those with more challenging decisions?

Rating:  4.56


25 Apr 2004 - by Douglas Zare

Streaks make a good story, so we often hear about them. To argue that the dice seem nonrandom, people report improbable streaks. In this column, we'll look at the theory behind streaks of random and nonrandom events.

Rating:  4.29

Who Is Holding Whom?

25 Mar 2004 - by Douglas Zare

Backgammon is a race with obstacles. It is relatively easy to understand the race but hard to understand the obstacles, and how they affect the race. Though not the most common view of backgammon, it is particularly useful in holding games.

Rating:  4.60

Chouette Survival

25 Feb 2004 - by Douglas Zare

My first trophy came from the Chouette Tournament at the 3rd Boston Open. I had faced some tough, unusual dilemmas. Here are a few of those along with some analysis of the tournament equity.

Rating:  4.86

The Last Rolls - Part 2

25 Jan 2004 - by Douglas Zare

In Part 1 we considered the theory of the bearoff near pure n-roll versus n-roll positions. In this second part, we consider actual examples of close cube decisions where one side is close to an n-roll position.

Rating:  3.86

The Last Rolls - Part 1

25 Dec 2003 - by Douglas Zare

Since high cubes are often exchanged at the end of the game, it is valuable to be able to judge the late bearoff accurately. Let's review the theory of 2-roll, 3-roll, and 4-roll positions and see the effects of each nonworking double or misses.

Rating:  4.82

The Kelly Criterion

25 Nov 2003 - by Douglas Zare

The Kelly Criterion for rational gambling with an advantage is familiar to serious card counters in blackjack, but many strong backgammon players are not familiar with it.

Rating:  4.78


25 Oct 2003 - by Douglas Zare

The mathematical theory of voting is surprisingly deep and some of the complexities show up in backgammon. This is not easy, and it is quite possible for a team to fail to make the most of its resources.

Rating:  3.60

When To Count

25 Sep 2003 - by Douglas Zare

Most of the time, having a feel for the position is more important than any calculation, but sometimes we need to count something. Here, we will focus on what to count, and when it is important to count.

Rating:  4.95

Cube Vs. Checker Play Errors

25 Aug 2003 - by Douglas Zare

What distinguishes experts from each other and from advanced players, checker play or cube play?

Rating:  4.70

Cube Vigorish In Money Play

25 Jul 2003 - by Douglas Zare

In money play, a perfectly efficient double is a borderline take/pass. Cube vigorish can be used to measure the efficiency of doubles.

Rating:  5.00

Robertie's 5 And Michael's 432

25 Jun 2003 - by Douglas Zare

Closeouts can lead to the gammons but are also a route to victory when you hit your opponent after he has started to bear off. Let's look at some of the resulting positions, and two heuristics, to help you to estimate winning chances.

Rating:  4.82

The 2:1 Rule

26 May 2003 - by Douglas Zare

There are many formulas that can be used to try to reconstruct the match equity table over the board. These include Janowski's formula and Neil's numbers. Here's a new method, the 2:1 rule, that covers some additional cases.

Rating:  4.67

The Effective Pip Count

25 Apr 2003 - by Douglas Zare

The pip count is a simple way to assess most races, including races to save the gammon but in many situations, the raw pip count is unsatisfactory, and must be adjusted.

Rating:  4.82

Match Play Vs. Money Play

25 Mar 2003 - by Douglas Zare

I have often looked over positions from matches of mine and been dismayed by a bad take/pass, but thought, "At least it would be a take/pass for money." Well, how much of a difference does it make? Quite a lot!

Rating:  4.17

Woolsey's Rule In Match Play

25 Feb 2003 - by Douglas Zare

Woolsey's Rule is supposed to encourage you to double when doubling is correct, but here we'll concentrate on doubling when it is wrong, bluffing.

Rating:  3.89


25 Jan 2003 - by Douglas Zare

Just as musicians practice making a single note beautiful, backgammon players should benefit from asking, "What is the purpose of doubling?"

Rating:  4.56

Giving Gifts

25 Dec 2002 - by Douglas Zare

If someone offers to flip a coin to decide whether to take or not, double without hesitation.

Rating:  5.00

Evening The Odds

25 Nov 2002 - by Douglas Zare

The basic idea of parity is easy, but many serious players err in the execution, applying parity too much or at the wrong time.

Rating:  5.00


22 Oct 2002 - by Douglas Zare

Rollouts are one of the most powerful tools for assessing the value of a position. This article intends to help illustrate what information we can or can't get from them, and help guide the process of choosing which rollouts to perform.

Rating:  4.89

What's Normal?

22 Sep 2002 - by Douglas Zare

There are some very simple calculations based on the normal distribution that help one to understand results from rollouts and money sessions.

Rating:  4.56

Janowski's Formulas - Part 2

22 Aug 2002 - by Douglas Zare

In this article, we will consider Janowski's formulas for cubeful equity when not too good to redouble and the redoubling point.

Rating:  4.20


22 Jul 2002 - by Douglas Zare

Volatility is about how much is riding on the next roll or exchange and when to double - it is usually correct that you need an advantage and a volatile position, but sometimes this is misleading.

Rating:  4.88

The Early-Late Ratio

22 Jun 2002 - by Douglas Zare

In Snowie's theory panel, you can find a lot of information about match play according to Snowie's match equity table. One statistic for a match score and cube level is the early-late ratio. What is this ratio and how can you use it?

Rating:  4.92

Janowski's Formulas - Part 1

22 May 2002 - by Douglas Zare

Rick Janowski has created many formulas relevant to backgammon. As we look at the Janowski take point formula for money play, we will see the continuous limit model of backgammon and cube liveliness.

Rating:  4.00

Reflections On Two Problems

22 Apr 2002 - by Douglas Zare

In pure mathematics, the reflection principle is a clever idea that sometimes produces simple solutions to hard problems, or relates apparently different phenomena.

Rating:  4.27

Aggression Following Closeouts

22 Mar 2002 - by Douglas Zare

As I try to understand aggression in backgammon, let's focus on checker plays in positions resulting from closeouts that many players get wrong. Although these errors are not individually very costly they do arise frequently.

Rating:  4.71


22 Feb 2002 - by Douglas Zare

Tournaments thrill the participants and spectators. But is there any theory involved? Surely the correct strategy is just to play your best in each match, right? Let's look at this a little deeper.

Rating:  4.50

Bot Confusion

22 Jan 2002 - by Douglas Zare

Bots have positive and negative confusion levels.

Rating:  4.36

Using All The Points

22 Dec 2001 - by Douglas Zare

Is match play like money play if both players can use all of the points?

Rating:  4.00

Gammon Price

22 Nov 2001 - by Douglas Zare

Gammon price is how valuable it is to win at the current cube level but how valuable it is relative to the value of winning a single game rather than losing.

Rating:  4.65
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