Backgammon: Programmable players

IF YOU are a reasonable chess player and want to pit your wits against a machine, rather than another human being, to help you improve your game, then you have no problem. You can buy a sophisticated set with a touch-sensitive board, a hand-held portable or software for your PC.

The one thing you can guarantee is that unless you are one of the 50 or so top players in the world, there is a chess-playing program that can beat you - I know, I own several such programs.

But what about the backgammon player who wants to do the same as his chess-playing colleague? Sadly, he is not so lucky. In recent years a number of elegant backgammon- playing computers have come on the market. Unfortunately, appealing though they may be to the eye, their standard of play is not much better than beginner level.

Similarly, software available for PCs is of the same standard. One of the main reasons for this is that none of them is capable of handling the doubling cube well in any except the most simple situation.

Why the discrepancy between the two games? One reason is that chess has had far greater media exposure, is more popular and has thus attracted far more significant investment. A great deal of time and money has gone into raising chess programs to their current level.

Unfortunately, the techniques that have been so successful in the development of chess programs are only partially applicable to backgammon programs and no one, until recently, has solved the more difficult problems involved in backgammon programming.

As mentioned earlier, the complexity of coping with the doubling cube has defeated the majority of those who have attempted it. Efficient handling of the doubling cube is the very essence of backgammon and any good program must be able to use the cube competently.

Backgammon computers have been around since 1919 when Gammonoid, programmed by Hans Berliner, a chess master and former world correspondence-chess champion, beat the then world champion Luigi Villa. Although Villa technically outplayed the computer, Gammonoid rolled good dice when it mattered most and won the match 7-l. Until recently there has been very little progress. However, in the last couple of years significant strides have made in the US.

Firstly, there is now a program on the market which can play a reasonable game against the majority of players. This is Expert Backgammon, which is available for both the PC and Macintosh (the PC version is currently stronger). Although not master-strength, Expert Backgammon is certainly far stronger than its rivals and has some useful additional features, such as being able to suggest moves for you if you don't know what to do. It can also play at several different skill levels and the vast majority of casual players would learn from playing against the program.

Secondly, Dr Gerald Tesauro is developing a program called TD-Gammon, using neural network technology. Employing this technique, the rules of the game were programmed into the machine and from then on, it taught itself what constitutes 'good backgammon' - initially by playing itself 300,000 times. It recently played the twice world champion, Bill Robertie, for an entire day. Although Bill won, the match was close.

TD-Gammon is undoubtedly the strongest playing program in the world today. Given another year or so, it may yet overtake even the best players in the world - a sobering thought. TD-Gammon is not being developed for commercial use, as its author is using it purely to test the validity of the learning theory it employs. However, I do not think it will be long before a clone finds its way to the market-place.

Readers wishing to find out how to obtain copies of Expert Backgammon or details of backgammon magazines and products currently available from the US, may send an SAE to Chris Bray, Miscellany, The Independent, 40 City Road, London EC1Y 2DB.