backgammon

How do you evaluate positions which aren't in your reference set? Take this position. Black is on roll, should he double, and should White accept or pass? Over the table there is no solution for an inexperienced player, but what you can do is to note down the position and then later perform "a rollout".

A rollout involves playing the game out to a conclusion from the given position a number of times and logging the results. Normally at least 36 rollouts are performed, and the first move for the side on roll is rotated through the 36 possible rolls of the dice: the first game Black starts with 1-1, the second with 2-1 and so on. Rollouts are normally performed with the cube in play. To stop the cube getting to ridiculous heights all doubles/redoubles are assumed to be drops.

After tabulating the results, it is possible to tell the correct cube action for the given position. Extensive rollouts of the diagrammed position show Black winning a plain game 36 per cent of the time and a gammon 25 per cent of the time; White wins 35 per cent plain games and 4 per cent gammons. These figures show that Black should double and White should take. Rollouts are often used to determine which is the better move in a given position.

Computer programs are now available that will perform thousands of rollouts while you sleep. However, there is no real substitute for doing the work yourself, as you learn so much about the position as you roll it out.