Simborg Interviews
Interviewed by Phil Simborg, January 2011
Xavier Xavier Dufaure de Citres has brought to the backgammon community eXtreme Gammon but also GammonSite and, in the past, NetGammon.

Tell us something about your yourself and your background.

I am 42. I grew up in France, in Savoie to be precise, with my parents and my two brothers. I graduated from college in Grenoble in electrochemistry and electrometallurgy. I never used these skills since I left college as I started working in the software industry right away.

I started to work for Borland as a Language Tech support specialist. I learned a lot but after one year it got boring and I found a job at GOTO software. I brought with me the backgammon program I had made (CyberGammon) and created NetGammon for GOTO.

This project will always remain very dear to my heart as it is on NetGammon that I met my wife Michelle.

I moved in the USA in 1998 and we got married in 1999. We have been living in Massillon, OH ever since.

What do you do for a living?

I am a project manager in a small company (45 employees) that writes software for the food industry. I am more specifically taking care of the SQL database development and the data warehousing.

How did you get introduced to backgammon?

My first exposure to backgammon is a bit unusual. Around the age of 11 my older brother and I were receiving a magazine called Jeux & Strategies. It covered a wide variety of games (wargames, logic puzzle, math puzzles, etc.) and had a section for the "great classics": Chess, Draughts, Othello, bridge, tarot, go and backgammon.

The backgammon section was made by Benjamin Hannuna. It was typically an 8 position quiz. I got interested in the game and started learning from the Hannuna's comments. So, strangely, I started backgammon by solving problems rather than actually playing. I tried to get my brothers and father interested but without success. (The fact that I was a very bad loser at the time probably explains why.)

I did not play backgammon until I went to engineering school (college). At the time I did not have a board so I wrote my first backgammon program (no engine, just an interface to play and store results).

How strong a player are you?

I am decent level, but far from the top. When paying attention I play around a PR of 5.0 on average.

What advice would you give to a new player that wants to become a top player some day?

Get eXtreme Gammon, of course! Also, read books or get some lessons with Phil Simborg! Programs are great at spotting your mistakes, but without the basis to understand why you actually made a mistake it will take longer to progress.

What's the best backgammon book or article you've ever read?

I've always enjoyed Chris Bray's, Backgammon, An Independent View. Robertie's 501 Essential Positions is also something I often reopen.

What are you really good at besides backgammon?

I am quite good at logic puzzles. I like games in general and I can play most of them correctly but backgammon is still the one I am strongest.

I am good at programming and have a strong mathematical background (Math Spe M, for those who know the French educational system).

How do you relax other than playing backgammon?

I enjoy watching movies and playing games on the computers. Also, my wife Michelle and I always enjoy going out to a restaurant with good food and good wine.

Who are your heroes in backgammon, people you respect either for their play or for other reasons?

I am very impressed by how fast and accurate players like Neil Kazaross, Stick Rice, and John O'Hagan can be.

Has your game improved much in the past few years? If so, why?

Not so much in the past two years because I've been more busy programming than playing. But in the years before that, my skill improved a lot. XG was getting mature and I was playing the bot a lot. I was focusing on getting the right moves and did not care about the result.

How did you happen to start GammonSite, a backgammon playing web site?

As I mentioned before, I moved to the USA in 1998. I started to work on a Gaming site. The site (GameSite 2000) opened in 2000 and included Chess, Checkers, Reversi and Backgammon.

The other games never caught on and were later dropped, and the site was renamed GammonSite.

Tell us a little about GammonSite.

GammonSite offers ratings, chat, tournaments and long duration leagues. Everything is highly configurable. It's a friendly site for casual games, but experts are welcome. We have tournaments scheduled every half hour.

How did you happen to develop Extreme Gammon?

eXtreme Gammon started when Oasya (Snowie) told us they would start charging money to have their program running on GammonSite. As we did not want to (and couldn't) pay the requested price, I started to work on an engine. After a few months, we were able to replace Snowie with our program.

A year or so later, I thought I had a decent enough engine and started working on the interface. I worked on and off for about 5 years. Around 2008, we started to think about making it available commercially and started working in that direction.

Phil Simborg came to GammonSite around that time and I happened to mention XG to him. I sent him the program and his enthusiasm about it showed us we had a product that would be interesting to users. We released the program in June 2009 and have been very happy with how the product was received.

How is Extreme Gammon different or better than Snowie and Gnu Backgammon?

The first thing I programmed into XG was that I wanted all the analysis to be done in the background. I always found very annoying to have to wait for the results while I could start checking my mistake.

This is the main difference with our competitors on the interface/usability side. The two other main differences are speed and strength.

Speed took a long time to achieve. Optimizing the core routine of XG in assembler was very fun, but it's a long and complex process. (To give you an idea, I estimate I can write the same code in Delphi about 20 times faster than in assembler; however the assembler code will be between 5% and 20% faster.)

Speed optimizations, however, are challenging and have an instant gratification. (If I find an optimization, I can just calibrate and see immediately what I gain). Strength is the opposite: You make a very simple change, let's say in the cube efficiency and then in order to test that change you have to let the computer self-play for a couple days before seeing the results.

I think XG surpasses our competitors on both Speed and strength. The Depreli Study and Phil's study of positions that Snowie and Gnu missed in Michael Corbett's book very clearly proved this to be true.

Are you working on a new, improved version of Extreme Gammon? What features will it have? How will it be improved? When will it come out?

Yes XG2 work started in June last year. I started with retraining the neural network. The details of it are "trade secrets" so I won't discuss them. However, the retraining required the analysis of 73 trillion positions! Even using a multiple core i7 (up to 8 cores), it took several months. Big thanks to Neil Kazaross, Claude Landry and Miran Tuhtan for contributing their CPU power to that effort.

I am glad to say that we achieved a better improvement than we targeted. On 3-ply, it has increased by 13.2 Elo (or 0.4 PR) and we would have been happy with 10. We also achieved even more significant improvement on back games. Thanks to Neil Kazaross for his relentless effort to push me in that direction and his valuable feedback as the process unfolded.

Mochy and Phil Simborg have also helped in the trials and have provided excellent ideas and feedback.

The other changes are interface improvements. The non-exclusive list is: Clock play, batch rollout, translation into other languages, new position export features, new HTML export, opening book using all the rollouts made by the community on

Release time is expected to be in June of 2011.

How would you compare eXtreme gammon to the best players in the world? Are there any specific areas of the game where eXtreme gammon is not as good as the best players in the world?

Neil, Mochy, Stick or any other giant can surely answer this better, but I think that XG (Version 1) is globally stronger than any human player. Back games are surely the positions XG understand the least but hopefully this is improved in the upcoming version.

Do you think internet play of backgammon will continue to grow in the future? How will we ever be able to play online and be confident that no one is cheating?

Playing for money against people you do not know conveys a risk that your opponent is using a bot. As computers get faster, it makes it easier for people to use them while playing, they don't have to wait any noticeable time for a 3-ply analysis. I think that's why money games have drastically decreased on the internet (along with the outrageous rake on most sites).

Sites for casual play, such as GammonSite, do still have their place and I am sure will continue to grow as more people access the internet.

Do you ever hope to give up other jobs and devote your time to backgammon?

I wish, yes. I do not give up hope, but I would say this is quite unlikely that I would be able to do that anytime soon.

Do you ever intend to start playing in live competition?

Maybe, yes, I am procrastinating about that. Let's say I am seriously thinking about it.

Thank you to Phil Simborg for sharing this article.
You can contact Phil at:
or visit his web site:

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