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10.1.8 Changing evaluation settings

A typical evaluation settings dialog is shown in this figure.

The evaluation settings dialog


The dialog is consisting of two columns, the left column is for setting the checker play decision evaluation settings, and the right column is for setting the cube decision evaluation settings.

For each column you can select some predefined settings, or you can define your own settings.

In the lookahead box, you can adjust the lookahead of each evaluation by specifying the plies to be evaluated. Each ply costs approximately a factor of 21 in computational time. Also note that 2-ply is equivalent to Snowie's 3-ply setting.

For evaluation deeper than 0 plies, it's possible to reduce the number of rolls to evaluate in the lookahead. This can be set in the Reduced evaluation box. Instead of averaging over all 21 possible dice rolls it is possible to average over a reduced set, for example 7 rolls for the 33% speed option. The 33% speed option will typically be three times faster than the full search without reduction.

In the box for Cubeful evaluations, you can specify if you want GNU Backgammon to evaluate the cube ownership in it's evaluations. With this option turned on it generally improves the evaluation, specially when it's close to cube decisions, so we recommend that this option is turned on.

In the Noise box, you can add noise to the evaluation. This can be smart if you think the program plays to strong. You can use the Noise box option to introduce noise or errors in the evaluations. This is useful for introducing levels below 0-ply. The lower rated bots (e.g., GGotter) on the GamesGrid backgammon server uses this technique. The introduced noise can be deterministic, i.e., always the same noise for the same position, or it can be random.