All About GNU

by Albert Silver

By now, it's fairly common knowledge that just about all the top players make use of the neural-net backgammon programs such as Snowie, or the older Jellyfish. The impact these programs have had on the way the game is understood and played cannot be understated. Players of all levels have the option of purchasing these revolutionary 'bots' (short for robots) in order to not only have the pleasure of getting a drubbing by a world-class opponent as many times as they want, but also have it analyze their moves, games, and matches. The program will point out our mistakes, tell us how big a blunder our move was, and list the best moves. It is still up to us to understand why our move or cube action was wrong, however there is no question such a tool is priceless.

Perhaps 'priceless' is a poor choice of words as the price is by no means a given. Though the programs come with different options depending on how much one is willing to spend, a version with all the trimmings, such as importing one's matches, analyzing the games, grading your play, allowing rollouts, etc. will set you back no less than $380 for Snowie or 'only' $220 for the older, and less sophisticated Jellyfish. This would seem to indicate that a top-quality aide is only in reach of someone with deep pockets or a deep commitment. If not, one has to look at some of the free offerings available on the Internet.

That's where GNU comes in. Personally, when I first heard of GNU Backgammon, I immediately remembered with a grimace my first experience with an old version of GNU Chess several years earlier: an engine that barely played at an expert level, as opposed to other master-level programs, an absolute bare minimum in functions, and graphics that reminded me of my first Atari video game system ... from back in 1977. The surprise that awaited me couldn't have been greater.

GNU Backgammon is first of all a neural-net program of World-Class strength. It is based on the same technology from which Jellyfish and Snowie originated.

Neural Net technology

The concept of neural-net technology is what permitted the breakthrough in playing levels from 'interesting amateur' to 'world-class' playing literally on par with the best in the world. The person behind this brilliant idea is Gerald Tesauro, a researcher for IBM, who built the first neural-net program called TD-Gammon. The difference it brought was that instead of simply using weights and strategies of programmers and players, it created its own by playing against itself hundreds of thousands of times, with each version stronger than the previous one. By version 2.1, which had played 1.5 million games, two-time World Champion Bill Robertie declared it as good as a strong master and even wrote a book on the experience called "Learning from the Machine". In fact, because of its independent learning, its play and that of subsequent programs using neural-net technology have revealed revolutionary strategic knowledge of the game from which top modern practice is based. GNU Backgammon is among those neural-net giants, and is among the top programs in the world.
 

On GamesGrid, the famous online server where many of the world's best play, an older version of the engine plays constantly, and has achieved a rating as high as 2086. One bot, GGRaccoon, on a weaker setting, though playing instantly, is a favorite sparring partner of the top players there. The current GNU is two versions later, just as fast, and stronger. It is also constantly in development.

Furthermore, the interface and functions it offers everything a player needs and more:

Advanced players will also find a wealth of options with: The interface's appearance can be changed according to a quantity of skins available, and the board appearance can also be changed according to a large number of settings with ready-made designs.


What follows is a tutorial intended to present most of what GNU Backgammon has to offer, though not exhaustively so, and how to make the most of it. Therein you will find out about:

Feel free to skip over parts that do not interest you or that you already know.


Where to get it

The official site of GNU Backgammon is either http://www.gnu.org/software/gnubg/ or the new site at http://www.gnubg.org though you should be warned that this is not where you will want to get the program. To get the fully functional version you want to go to the site of one of the authors: GNU Backgammon for Windows. Go there and download the Installation Archive, a self-installing 11 MB file, and run it to the GNU developers.

Just so you know, there is a rather spooky warning below that says it is for people who "can live with software that suddenly crashes with no sort of warning (…) and like reporting bugs". Frankly, it's not nearly so dire, so don't be put off by this. Of course if you do find a bug, or have a suggestion, do not hesitate to send it.

Once you have done this, you will want to bring it up-to-date with the latest version, released very regularly, to enjoy the new features and bug corrections. For this, go to Nardy Pillard's site This is not an 'official' GNU Backgammon page (for all practical purposes it is). There, scroll down to the part that says Latest Build and download the most recent file. The numbers aren't some mysterious serial number but merely the date of the release. So Build 021227 would just mean Build of 2002 December 27th.

Using the new build/version requires a little handiwork, though nothing too hard. When you download it and double-click on it, it will install it into the C:\Program Files\gnubg directory with the name gnubg-021227.exe for example. The problem is that the shortcut on your desktop is linked to the original gnubg.exe file, so if you double-click on the icon it will still load the old version.

Enter Windows Explorer, and go to the directory C:\Program Files\gnubg. In it you will see the old file gnubg and the new one gnubg-021227. You may or may not see the extension. Delete the old file gnubg, or rename it to something else, and then rename the new file to gnubg (if you don't see the extension) or gnubg.exe if you do see the extension. You can always check if the right version is running by going to the Help menu in GNU and selecting About gnubg.

Playing a game

The first and most basic feature is to simply set up a game and play, so let's start with that. Start the program and maximize the window. If the appearance isn't to your liking, you will find out how to customize it further below.

Players

First set the settings by clicking on the Settings menu at the top, then click on Players. This opens a window displaying the settings for GNU or allowing you to play against someone else (or even have GNU play against itself). At the top there is a tab where you can also set your name for the player. For the GNU engine, I prefer the pre-defined setting of World Class for both checker play and cube decisions. At this setting it will take some time to play at given moments, so if you want a top-notch game, just a fraction worse, but almost instant, select Expert instead. You may also get tired of getting beat up by it (if you think it cheats, read the section A Word about 'Cheating'), in which case, you can select more modest playing levels.

I also set the Move Filter to Huge. This guarantees it will examine the most moves in depth though making it a bit slower at World Class level.

Move filter

The move filter allows you to control exactly how many moves GNU is examining at each ply. A ply is basically one move played by one side, thus if both sides played a move, it would be one whole move, but two plies, one for each side. To change the specific settings, press the Modify... button.

If you are playing Expert level or another 0-ply setting, the Move Filter settings will not change a thing, as Expert level automatically examines all moves. At World Class level, this changes though as it takes a selection of the best moves from 0-ply and examines them at 2-plies. This means that for those moves it will calculate all the possibilities 2 plies ahead, evaluate them, allowing it to find better moves in some cases. Since World Class is a 2-ply setting, we are only interested in the 2-ply settings of Huge as in the above figure. 3-ply or 4-ply settings will have no effect here therefore. There we can see it will select the top 7 moves from the 0-ply evaluation, plus a further 6 moves if they are within a 0.200 equity difference, and analyze them at 2-plies.

Playing options and Tutor

In the Settings menu, select Options, and a small window opens. Here, you can activate automatic bear-off (it will automatically take off the most checkers if it can sparing you the effort of playing obvious moves), the direction of the moves (check or uncheck clockwise movement), choose the equity table to be used (Woolsey's, Snowie's, etc.), select Nackgammon, choose to play with manual dice (you play with your own personal dice instead of the computer's) and a great teaching tool: the Tutor Mode.

When activated, the Tutor mode has GNU analyzing your moves and/or cube decisions and comparing them with its choices. You set the threshold for its alerts, so if you set it for bad, it will only warn you when you make a bad mistake. It will then allow you to re-examine your choice, go right ahead with it, or provide a 'hint' essentially showing you its analysis.

My personal choices are to set the limit to bad, and to set the Tutor decisions as Same as Analysis.

Tip:  Before going any further, do not forget to click on Save settings at the bottom of the Settings menu. You must do this every time you make changes you wish the program to remember the next time you load it.

Starting a game

To start a game, just click on the File menu, and choose New, and then your choice of a game, match, or money game session. When you are playing, it will automatically show the pip count (and difference), though you can de-activate it by going to Settings menu and in Appearance uncheck the box Show Pip count permanently.

While playing, you can access the main functions through the toolbar at the top:

Rolling the dice, doubling, taking or passing a double (thumbs up, thumbs down), redoubling (beavering) etc. Mind you, you can roll the dice simply by clicking on the empty space of the board on the right side. Same goes for doubling, where you can just click on the cube on the board.

If you would like GNU's analysis of a move or cube decision while playing, go to the Analyse menu and select Hint, or press the keyboard shortcut Ctrl-H. For details on the Hint/Annotation window, see below.

Advanced Playing Information

For players seeking more advanced information on the position, GNU also provides information on the Match Equity Table (MET), race theory (Kleinman count, Thorp count), not to mention a powerful Market Window/Gammon value viewer.

The Match Equity Table can be viewed at any moment by entering the Analyse menu and selecting Match Equity Table. There you will see table values including Pre-Crawford and Post-Crawford scores. The table used by GNU is by no means imposed, and you can select any of a number of provided ones, including the Snowie MET, Woolsey's, Jacob and Trice's, etc. by selecting Load Table.

If the game situation is a race, one can look up what the Kleinman count or Thorp count has to say about it.

Finally, GNU offers a powerful Market Window/Gammon value tool to the advanced or aspiring player. This will provide immediate information on the take point, double point, etc. for both players at any match situation, including side-by-side dead-cube/live-cube scores. If you wish to see how other match scores would affect the figures, you can simply use the arrows, and you can change the cube value. If it is a money game, then the respective double, beaver, raccoon, redouble values will be shown instead.

Importing and Exporting games

GNU allows users to import matches from a variety of formats, including the Jellyfish formats (.mat - also used at Truemoneygames BTW), the FIBS oldmoves format, and the Snowie GamesGrid format (.sgg). Just go to the File menu and choose Import. This will allow you to use its great game and match analysis functions. Below is a tip if you are a Snowie user and wish to compare notes.

Tip: For those who take online classes, please note that it imports the commentary saved on a move-by-move basis at GamesGrid, so you can see comments in the annotation window when going over the moves. I tested this with an online class and it was all there, neatly saved at every move.

Snowie Users Tip: Although it is not well-documented, it is perfectly possible to export matches or money sessions from Snowie to view and analyze with GNU. To do so, open your match/money session in Snowie, then go to the File menu and select Export, and then the top-most option Standard text format... choose a name and save it (remember the directory you save it in) such as Shonga-Grandell.txt. The untold secret is that the 'Standard text format' is simply the classic Jellyfish .mat format. Having done this, in GNU, go to the File menu and select Import, then .mat match… locate the directory you saved the match in, and select the .txt file. You can also export your GNU matches to Snowie by inverting the process. In GNU, export your match/money session with File Export Match (even if it was a money session) .mat. Then in Snowie, go to File Import file Jellyfish log file and open the file you saved with GNU. Experience has shown that seeing where they disagree on what the errors are, often shows a mistake in analysis/evaluation from either side, and GNU is certainly not above spotting blunders by Snowie, so this allows one to get a little closer to the truth.

It also allows users to Export their games and matches into a variety of formats such as the Jellyfish formats, text format, not to mention PDF, LaTex, PostScript, and even HTML. Note that when exporting to these formats you get the moves, diagrams at each move, and the analysis. In text format you'll see boards in ASCII art, and in PDF, you'll literally get an instant e-book of the match.

PNG Image export

You may also wish to simply save the board position as an image file that you can add to a Word document or HTML document for example. To do so, go to the File menu and select Export, then Position, and PNG. Be careful to add the extension when saving it, or you will have trouble viewing it. In other words, add .PNG to the name when saving the image. The board image saved will use the color scheme currently being used. If you wish a different color scheme, change the design (for more info see Appearance -- Boards). You can also change the size of the image that is created by entering the Settings menu, then Export, and at the bottom right of the window that opens, set the size you want.

HTML export

A special note needs to be added regarding the HTML functions. First of all, to set all the settings as you'd like, you need to go to the Settings and then select Export. There you can choose, down to the smallest details, what it will display and how. The 'how' concerns the images used to produce board positions. This is chosen at the bottom of the window and you can choose between its own HTML images or two others, which are FIBS and BBS.

You can choose exactly what the board in the HTML page will look like, and have it appear exactly as the board design (see Boards for more on this) you are using in GNU. To do so, you need to create a directory to place the images and then export them. First, go to the File menu, select Export, and then HTML Images.... Find a directory to place them in, or create your own by pressing the Create Directory button at the top. I'd suggest using the default name \html-images. Now enter the directory and press the OK button. Note that you should not have a name in the bottom. Be careful to remember the name of the directory you placed the images in, including capital letters if you used any. Now go to the Settings menu, select Export and then at the bottom select GNU Backgammon board images (circled in red below) and enter the name of the directory.

Tip: If you want to post a position in an online forum that supports HTML you can do this regardless of whether the forum itself supports the necessary images. Here's how:

  1. First be sure the image to be exported is currently on the board, and then in the Export settings set the HTML board type to fibs2html. In the space below URL to pictures, enter http://fibs2html.sourceforge.net/images/ as shown below. Be sure to click Ok, and then Save Settings.

  2. Go to the File menu, and select Export, then Position, and then HTML. Save the file and then open it in Internet Explorer. In case this already sounds a bit mysterious, inside IE just go to File Open and click on Browse.... Locate the HTML file you saved and open it.

  3. Once you see the board and image in front of you, still in IE, go to the View menu and select Source.... This will open a small window with a lot of code. Copy the entire contents to the body of the post you are writing, and the board and analysis should appear in the forum without any problems.

GammonLine HTML Export

If you are a GammOnLine subscriber, enjoy the GammOnLine BBS, and would like to share an interesting position, the above tip will do the trick, but you can also make use of the GammOnLine board images as seen in pretty much every article available. To do this:
  1. Go to the File menu, and select Export, then Position, and then GammOnLine (HTML).... Save the file and then open it in Internet Explorer. In case this already sounds a bit mysterious, inside IE just go to File Open and click on Browse.... Locate the HTML file you saved and open it.

  2. Once you see the page and analysis in front of you (you won't see the board though so don't worry), still in IE, go to the View menu and select Source.... This will open a small window with a lot of code. Copy the entire contents to the body of the post you are writing, and the board and analysis should appear in the forum without any problems.

Analyzing matches

GNU also comes with a set of functions that allow it to analyze a game or match, provide a detailed graded report, and allow you to navigate through the moves to quickly see the mistakes made.

Before starting, you'll want to configure the settings first, though this will only need to be done once. Go to Settings and select Analysis. A fairly large window will open, allowing you to fiddle with as many settings as you could want. This is also where you set the thresholds for the Tutor mode (dubious, bad, etc.). Feel free to look around, but I simply set this to analyze checker play, cube decisions, and luck, and set the level of analysis at World Class for both checker play and cube decisions, and then the Move Filter to Huge. The Move limit is the maximum number of moves it will display in the Hint/Annotation window.

Tip: Once more, please do not forget to save (SettingsSave settings) after making changes in the settings, or you will be forced to change them again the next time you start the program.

If you just played a match at an online server, import it first, then go to the Analyse menu and select Analyse match, or Analyse Session (money game session). If you only want to analyze a specific game, open it and then select Analyse game. Once started, you will see a bar in the bottom right corner showing the progress made in both the number of moves and percentage completed.

Analysis Results and Grade

Once GNU has finished analyzing your games, you'll want to see the report and then go over the bloopers. In the Analyse menu, select Match statistics, and a window will open. Feel free to resize it (clicking and dragging the edges) to show more information. It will show you the results of both players side by side, allowing you to quickly compare notes.

In the screenshot above you can see how it appears. It will detail bad moves (and good ones), not to mention rolls of varying luck, and attribute individual grades for your checker play, your cube decisions, your overall playing, and even your luck. It is very revealing when you see a very different evaluation of your checker play as opposed to your cube decisions. Another feature is that GNU only grades your checker play according to non-forced moves, so it won't declare you made no mistakes in 50 moves when 49 of those were spent on the bar. You can save these results with the match (File Save Match), so that you can see the analysis at anytime without having to redo it.

You can also copy the results of the report to another document. To do this, click on the lines you want to highlight using standard Windows functions (with the Ctrl and Shift keys), and then press the Copy button. Now open a document and paste (Ctrl-V) the contents of the clipboard.

Tip: If you use a program such as Word or WordPad (avoid Notepad), the formatting will be lost when you paste it, but this is easily fixed: in the document, highlight the text, and change the font to Courier New and size to either 9 or 10. Ex:

                                      Tami                 KitWoolsey
Error rate (total)                    -0.205 (-3.770%)     -0.147 (-2.810%)
Error rate (pr. move)                 -0.006 (-0.114%)     -0.004 (-0.074%)
Checker play rating                   World class          Supernatural
Rolls marked very lucky               0                    0
Rolls marked lucky                    1                    7
Rolls unmarked                        40                   34
Rolls marked unlucky                  0                    0
Rolls marked very unlucky             0                    0
Luck rate (total)                     +0.420 (+7.317%)     +2.497 (+45.772%)
Luck rate (pr. move)                  +0.012 (+0.203%)     +0.061 (+1.116%)
Luck rating                           None                 Go to Las Vegas imme

Player Records

You can keep track of the results obtained by yourself and your opponents using the Player Records. There you can store the statistics of your matches and keep records of the average results obtained such as checker play, cube decisions, and luck. It will also break down the results according to the last 20 games played, the last 100, etc.

To add results to an existing account, or simply create a new account in which to add the results (of course you must first have an analyzed match open), go to the Analyse menu, and select Add to Player Records and Match statistics. If the account doesn't already exist, GNU will create it automatically and add the results. If you wish to remove an account, then click on the name in the Player Records, and press the Erase button.

Reviewing moves and mistakes

Once you have seen the results of the report, you will probably want to go over the mistakes you made. To do this, you'll need to open two more windows: Go to the Windows menu and select Game Record, and again to open the Annotation window. Two more windows appear, one showing the list of moves, and the other the analysis. However, the first issue that most likely needs to be resolved is one of organizing them so as to be a practical study tool.

Windows layout

When playing, it is normal to prefer the largest board display possible, however, when reviewing moves this is not possible. The following layout is what I recommend for screen resolutions of 1024 x 768, and 800 x 600. It is possible to shrink the board of course to easier fit the information windows but reviewing full matches then becomes tiresome in my experience. Feel free to create your own of course.

First size the board to about half the screen width and drag the ends down so as to get a compact fit. If you are using an 800 x 600 resolution then I recommend using the smallest board size possible. Note that a bit of overlapping is inevitable. Here is an example of what it should look like:

Game Record

When opening the Game Record a small window will appear looking like this:

It always opens to the last move of the last game. You first have to click on a move in the notation before using the arrows. When you see a move highlighted, as seen above, you can navigate backwards and forwards move-by-move with the green arrows, and game-by-game with the red arrows. If you use the buttons with the question marks on the green arrows, it will go from mistake-to-mistake. In the example used, GNU disagreed with one move by Kit Woolsey. The move in question wasn't considered a bad mistake, but it did get earmarked as dubious. GNU adds these punctuation marks (standard in chess commentary) in order to identify how it evaluates a move. For example, a  ?!  indicates a dubious move, a  ?  indicates a bad move, and a  ??  indicates a real blunder.

Hint/Annotation window

In order to see GNU's analysis, go to the Windows menu, and click on Annotation. This is essentially exactly the same as the Hint window, except that the latter won't include a space to add written notes. You will see a window open showing the best to worst moves from top to bottom. A first suggestion is to go to the Settings menu, then Appearance, and in it, to the right, make sure the box for GWC as Percentage is checked. Here is what it shows for the dubious move shown above:

First of all, if you are new to backgammon software, and the above looks hopelessly complicated, relax, it isn't nearly that bad. Let's look at the 3rd line in red, the move that was played, and figure out what it all means:

As you can see, it shows the best moves considered, with the move actually played in red, plus the various equity scores for gammons, etc. Most players will focus on the last three, which are the total equity of the move, the difference in equity between the move played and GNU's top choice, and what move is being evaluated.

In the diagram above, we can see that at 2 plies GNU considers that 13/10* 7/1* was best, with 24/15 close behind. If you'd like to copy this information to a document, click on the moves that interest you in order to highlight them as above, and press Copy. Then paste it where you wish. Don't forget to change the font to Courier New size 9 or 10 if you wish to maintain the formatting.

You may also want to have GNU analyze a few select moves a bit deeper. To do this you can have it go a 3rd ply, or do a rollout. Let's have it do a 3-ply analysis of the three moves highlighted above. Just click on the number '3' and it will do a 3-ply analysis. Be a little patient as 3 plies is considerably slower than 2 plies, but it shouldn't be too long. If you want to customize the evaluator, click on the button indicated with a small red circle above, and change the parameters you want. Now just click on the Eval button, and let it compute its results. You may also prefer to see the Match Winning Chances of the moves instead of the equity. This shows the chances of winning the match as opposed to the evaluation according to a single game. To do so, press the MWC button:

Here we see the results of the 3-ply analysis, displayed in percentiles. We can also see that GNU now clearly favors 24/15 after deeper analysis. How about a rollout?

Rollouts

So what's a rollout? A rollout is when you have the program play against itself a set amount of times (number of trials) and then sum up all the results of wins, losses, gammons, etc. from those games to give a more precise evaluation of a move/position. The interest is that the program may easily be underestimating some features/dangers of a position, and not realize this by only looking a couple of plies ahead. By playing it out, things will happen, and the game will unfold, giving it more accurate information on the consequences of a move. One can do a full rollout, meaning it will play the position out until the last checker is born off, or it can be a truncated rollout, playing to a certain depth in plies, enough to evaluate the consequences.

Rollouts can be done at any time either directly from the Analyse menu with the Rollout option, or from the Hint/Annotation window. However, it is suggested you do it from the Hint/Annotation window as only there can you export the results to the clipboard using the Copy button. In both cases, the same options window is used as its reference. You will want to set your preferred options the first time by clicking on the [...] button to the right of the Rollout button.

I really only use one setting that gives excellent results within a few minutes and essentially only change the number of trials or the truncation.

My setting:

It should look like this:

 

Variance Reduction

Whenever running a rollout, you will always want the Variance Reduction activated as it greatly increases the reliability of the results. The first time this ingenious technique was introduced to backgammon rollouts was by Fredrik Dahl, the author of Jellyfish. In a nutshell, it factors in luck when evaluating results, so that the program doesn't need 10,000 games to average out the luck of the dice and that way be sure luck wasn't a factor in the results obtained. With it, 100 rolled out games with Variance Reduction can be the equivalent of 5,000 games with no Variance Reduction.
 

You will also need to set the playing level of the program in the rollouts. Click on the tab First Play Both as indicated by a red circle above. In the new pane, select Expert. Although it may seem like a shallow setting (0-ply after all), it bears reminding that GGRaccoon, a computer opponent at the online server GamesGrid, is set at this level, and is consistently among the top ratings despite the presence of some of the world's best players. It also plays at a superfast speed, allowing it to give results far quicker.

Once you have set your choices, press Ok, and then the Rollout button. When you are done, you may wish to copy the results to a document or e-mail for example. To do so, just click on the moves that interest you, and then press the Copy button as shown.

To see the results, just paste them on the document (Ctrl-V for Windows users).

1. Rollout          24/15                        Eq.:  +0.177
59.4%  18.0%   0.7% -  40.6%   8.8%   0.4% CL  +0.177 CF  +0.177
[  0.3%   0.4%   0.1% -   0.3%   0.2%   0.0% CL   0.006 CF  +0.006]
Truncated cubeful rollout (depth 19) with var.redn.
648 games, seed 1193803392 using Mersenne Twister
Play and cube: 0-ply cubeful [expert]
2. Rollout          13/10* 13/7                  Eq.:  +0.062 ( -0.115)
53.6%  27.0%   1.4% -  46.4%   8.8%   0.3% CL  +0.062 CF  +0.062
[  0.3%   0.4%   0.1% -   0.3%   0.2%   0.0% CL   0.007 CF  +0.007]
Truncated cubeful rollout (depth 19) with var.redn.
648 games, seed 1193803392 using Mersenne Twister
Play and cube: 0-ply cubeful [expert]

If you are using Word or Wordpad, it is suggested you set the pasted text to the font Courier New, and the size to 9 or 10, else the formatting will be lost, and it may be difficult to read.

Once more: Remember to save your settings before exiting the program or you will need to reconfigure your settings the next time you use GNU.

Setting up a position

Naturally, other than matches and games, you might just want to set up a position from a book or other source, and ask GNU's expert advice. First, you must start a new game or match, then just press the Edit button, located at the top in the toolbar.

At the bottom, you will now see you have the option of setting the scores or the names of the players. If you want to change the dice on the board, whose turn it is to play, or the doubling cube, you must go to the Game menu at the top, and at the bottom of the menu select your choice.

Moving and setting up the checkers is quite easy and Snowie users will feel at home as the method is identical. To remove or add white checkers to a point for example, use the right mouse button and click on the point. You determine the number of checkers to be added or removed by the height of the point you press. For example, in the following diagram,

if you have 5 white checkers on the 19-point and only want to have 3, click with the right mouse button on the 3rd checker where the yellow arrow indicates and the top two will be removed. Adding checkers is the same, so if you wanted to add a red checker to the 6-point you would place the cursor where the green arrow indicates and left-click. If you want to quickly get the starting position, you can click on the area indicated by the blue ellipses on the left, and if you want to quickly clear the board of all checkers, click instead on the right side on the area indicated by the pink ellipses. Try it and experiment a little. It's much easier to do than to explain.

To set the cube position and value click on the cube or enter the Game menu and select Set cube. A small window will appear with cubes set in all directions.

The cubes that are upside down are for the top player, the ones rightside up are for the bottom player, and if you wish to set the cube in the center, choose the ones facing sidewards. If you want the cube at its initial value in the center, choose the 64 cube facing sideward.

Once the position is set up, press the Edit button again to exit Edit mode. Now just go to the Analyse menu and select Hint (suggested even for rollouts).

Appearance

Skins

You can change the overall appearance of the menus through a number of skins included with the installation, however this cannot be done from within the program and must done manually. The procedure is fairly painless if you aren't afraid of moving a couple of files in the Windows Explorer.

Open Windows Explorer, and enter the \Program Files\gnubg directory. In it there is a directory called \Themes, where the skins are located, and in that, you will see a number of directories with the names of the skins they contain. Enter the directory you want and copy the files in it to the main \gnubg directory. It will ask you if you want to overwrite the files in it. Say yes, and start GNU to see the changes. It is important to copy and not move the files, so if you're not Windows savvy, this means holding the Ctrl key on the keyboard down while dragging the files. Keep the Ctrl key pressed when you let go of the mouse button. My favorite is the one called 'mac', and is what you see throughout this article.

Boards

The appearance of the boards can also be changed making use of a number of presets, or you can design your own. To make changes, go to the Settings menu and select Appearance. A window will appear, displaying a number of tabs at the top. Select Designs, and you will see a list of the preset board designs, as well as thumbnails of what they look like. To choose one, just click on the name of the preset and press Ok. That's all there is to it.

You can also make your own designs and save them. Using the tabs at the top, you can change the appearance of the board and if you really like your new design, go back to the Designs tab and save it by pressing Add current design and then Save designs. Send the GNU team your best ones, and they may include them in the next release, which is just about everyday by the way.

Conclusion

By now it should be clear that while a number of backgammon players have complained about the steep prices of top commercial software excluding them from the tools and type of progress available to more fortunate players, that complaint is now definitely without foundation.

It's true that it is ever a work in progress and has its rough edges, but with time they will undoubtedly be ironed out for the most part. It is also an engine that is stronger than its older top-of-the-line siblings in GamesGrid, and at its price (free), one would have to be crazy not to have it, even if one does own the legendary Snowie. After all, two heads are better than one.

I would like to effusively thank the authors of GNU Backgammon and its numerous contributors, and would also like to suggest that anyone enjoying their efforts make a contribution to the Free Software Foundation (FSF), the principal organizational sponsor of the GNU Project, as a token of appreciation. The FSF survives mostly off the contributions, however small, of private donations, and without it, those loud complaints mentioned above would be entirely justified.

A Word about 'Cheating'

By far, the most common complaint seen about all backgammon software, weak or strong, is that it must be cheating to get so lucky. Most of these complaints stem from a lack of understanding of probabilities, and how skillful play will affect luck or the possibility of lucky rolls.

To begin with, let it be stated that there is no bias of any kind, and the source code of GNU is open to any doubting it. If you still cannot believe it, feel free to use your own dice by entering the Settings menu and selecting Options, and then in the right side Manual dice. If you are rigorously honest about your results, you will find no difference in the long run.

Probabilities are what rule supreme in backgammon. As there is indeed an uncontrollable luck factor, one cannot guarantee a victory or loss no matter how stacked up the chances are. So, good backgammon strategy is designed to maximize the good rolls for the playing side, and minimize the good rolls for the other side. In other words, after the best play, there will be less good rolls for the other side. If the other side doesn't realize what is happening, then it will seem like a neverending streak of bad luck. It's not, it's the consequence of good playing. GNU is among the very best, so use it and learn with it. You can set it at a much weaker setting, and watch how its luck dries up.

The mathematics behind probabilities are also usually very poorly understood. Take for example the situation below. If your opponent had a checker on the bar, what is his chance of entering that single point?

If you said 11 chances in 36 or a little over 30%, good for you, but if you said 1 in 6 then you need a little brushing up. 1 in 6 would be correct if your opponent were only using one die, but with two, the chances add up to 11 in 36. So how come you never enter and GNU does? It may seem like that at times, but it's really not the case. It is natural to focus more on what causes us anguish making reality look quite distorted, but maybe you were very unlucky. Stories of hard luck abound. In a live game, I once played my opening move, and then lost to a backgammon without ever playing another move. My opponent hit me, and I danced for the rest of the game. I wasn't even able to avoid a backgammon. A top professional once told me of an instance where he was giving a gammon, got hit, and lost after dancing 7 straight times against a 3-point board. Does it seem to get more doubles? What about those doubles you rolled while on the bar? They don't count, you say? Sorry, but lady luck makes no case of guaranteeing the double will arrive at the right time. Good strategy will help you be able to use it when it does arrive.


Acknowledgements

I would like to thank the developers of GNU backgammon for their unprecedented generosity to the backgammon community and remarkable work.

Joseph Heled
Øystein Johansen
David Montgomery
Jørn Thyssen
Gary Wong

Although, the names of the contributors are numerous and deserving, special mention must go to Nardy Pillards for his tireless work in providing new builds almost every day at his site, and Achim Mueller for the GNU logo, his FAQ, and the new official GNU Backgammon site. A thank you to Tom Keith, the owner of the excellent website Backgammon Galore!  for converting this tutorial to HTML.

This tutorial may be freely distributed in any form, though modifications to the content may only be made with the author's permission. Questions, bug reports, or suggestions on GNU Backgammon may be sent to the GNU Backgammon e-mail. Questions or suggestions on the tutorial may be sent to the author.


Version 1.00
Copyright © 2002 -- Albert Silver