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11.1.1 Generate your own

GNU Backgammon is supplied with a program makebearoff that is used to generate bearoff databases. Due to various limitations it is only possible to generate bearoff databases with a size less than 2GB, i.e., the 13pt one-sided database and the 11 checker two-sided database are the largest databases that can be generated with makebearoff.

To generate one sided database issue

makebearoff -o 10 -f

to generate the one sided 10 point database. The program makebearoff uses a cache to store previously generated positions. You may set the cache size with the -s size option, e.g.,

makebearoff -o 10 -s 123456789 -f

to use 123,456,789 bytes of memory for cache size. In general, if the cache size is less than the size of the database to be generated, then extra time is needed to generate the bearoff database because some positions may have to be calculated several times.

makebearoff can also reuse previously generated databases, so if you already had generated the 9 point database you can reuse it:


makebearoff -o 10 -O -f

Note that makebearoff requires temporary disk space to generate both one sided and two sided databases. In general, twice the disk space of the database to be generated is needed.

To generate a two sided database issue

makebearoff -t 6x8 -f

This example will generate the 8 checkers on 6 points database. Again, it's possible to adjust the amount of memory with the -s option. It's recommended to set the cache size to the maximum amount of memory available (although there is no need to set it beyond the size of the bearoff database to be generated).

Other options for makebearoff are available, see makebearoff –help for the complete set.

The accompanying program makehyper is used to generate databases for Hypergammon. For example, to generate the 3-checker database issue the command

makehyper -c 3 -f

Since the generation is very time consuming makehyper will generate a checkpoint file (in the example above: that can be used to restart the calculation if needed by using the -r option. You can also change the default convergence threshold of 0.00001 if you're happy with less accurate equities. To generate the 3 checker database you need approximately 400 MB of free memory. On a 2.4 GHz box with 512 MB of RAM the calculation ran for 58 iterations of 3000 seconds each, i.e., a total of 48 hours!

See makehyper –help for the complete set of available options.