Node:Obtaining bearoff databases, Previous:Bearoff databases with GNU Backgammon, Up:Bearoff databases
gnubg 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 chequer two-sided
database are the largest databases that can be generated with
makebearoff.
To generate one sided database issue
makebearoff -o 10 -f gnubg_os.bd
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 gnubg_os.bd
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:
mv gnubg_os.bd gnubg_os9.bd
makebearoff -o 10 -O gnubg_os9.bd -f gnubg_os.bd
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 gnubg_ts.bd
This example will generate the 8 chequers 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.
At compile time the built-in one sided bearoff database is generated with the command
makebearoff -o 6 | makebearoff1 -o br1.c
which generated a 6 point one sided bearoff database. The database is
piped into makebearoff1 that generates the C code for the
database. The resulting br1.c is more than 8MB, so it's not
distributed with the source for gnubg.
The accompanying program makehyper is used to generate
databases for Hypergammon. For example, to generate the 3-chequer
database issue the command
makehyper -c 3 -f hyper3.bd
Since the generation is very time consuming makehyper
will generate a checkpoint file (in the example above:
hyper1.bd.tmp) 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 chequer 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.
You may download the two sided database with 6 chequers on 6 points from ftp://alpha.gnu.org/gnu/gnubg/gnubg_ts0.bd.gz and the one sided database with 15 chequers 6 points from ftp://alpha.gnu.org/gnu/gnubg/gnubg_os0.bd.gz.
Later, other databases may be available for download or it may be possible to purchase these on CDROM or DVD for a nominal fee.
To verify that your generated or downloaded bearoff database is correct, the table below lists the MD5 checksums for a number of possible databases.
The table below contains the MD5 checksums for the compressed one sided bearoff databases, i.e., databases generated with default options.
| Chequers | Points | MD5 checksum
|
| 15 | 1 | c789f049ec98ce4e307b471257999f39
|
| 15 | 2 | b6e61c1625ae4b3b164e93ab064192b9
|
| 15 | 3 | 346dae6139ccb4b227c534373e5c52e4
|
| 15 | 4 | 653255f5f9f22fd50277f7ff25b2a343
|
| 15 | 5 | 2064f9a56b23117d053a573c96a92fa2
|
| 15 | 6 | 3dc7b833c4670849cee00479a9e21b49
|
| 15 | 7 | 67235c8e0ee152df5daf36cbeae5b3c2
|
| 15 | 8 | a4acbb5c7e9e1f08e561afe0af934e5c
|
| 15 | 9 | 9c4ddab4e51c3e668c9c97b8f8768dbc
|
| 15 | 10 | 81b3898f06bbd08ee8295a839251a10a
|
| 15 | 11 | 78ecb4be86dab6af8755ea4063d50fb6
|
| 15 | 12 | 770fcff48894a96ebb2249343ef94866
|
| 15 | 13 | cc74b69a62f6e648936f533838a527a8
|
| 15 | 14 | not available
|
| 15 | 15 | not available
|
| 15 | 16 | not available
|
| 15 | 17 | not available
|
| 15 | 18 | not available
|
The table below contains the MD5 checksums for the default two sided bearoff databases.
| Chequers | Points | MD5 checksum
|
| 1 | 6 | 7ed6f8e7fce16ea2b80e07a4a516653c
|
| 2 | 6 | e9d760bf213841c285245ed757a52f4d
|
| 3 | 6 | 9d67da3db32ad4720cc38eecf9a67967
|
| 4 | 6 | 9156f37032d1d4b0352a41186e632dfc
|
| 5 | 6 | 0db19ab08feae1feb33ddbd709479f62
|
| 6 | 6 | 44b6040b49b46cb9dd2ce8caa947044d
|
| 7 | 6 | 9eb8b042d4d2ddf8d40e74a892745ad5
|
| 8 | 6 | fcdbbc80b7ef84ddc81b839d0f26bed1
|
| 9 | 6 | a11b2d410d51401143d05e73f9ffac15
|
| 10 | 6 | 12dc70c86f356d06bc96ee38dee40c62
|
| 11 | 6 | not available
|
| 12 | 6 | not available
|
| 13 | 6 | not available
|
| 14 | 6 | not available
|
| 15 | 6 | not available
|
As the generation of the Hypergammon databases are an iterative process it's not possible to give MD5 checksum for these, as it depend heavily on your convergence threshold, the number of restarts, and rounding errors.
Below is a random position from the database. The equities and percentages in your own database should be very similiar (if not identical):
GNU Backgammon Position ID: ADAAAQAkIAAAAA
Match ID : cAkAAAAAAAAA
+13-14-15-16-17-18------19-20-21-22-23-24-+ O: gnubg
| X X | | X | 0 points
| | | |
| | | |
| | | |
| | | |
v| |BAR| | (Cube: 1)
| | | |
| | | |
| | | |
| O | | | On roll
| O | | O | 0 points
+12-11-10--9--8--7-------6--5--4--3--2--1-+ X: jth
Player Opponent
Position 3018 2831
Owned cube : -0.0230
Centered cube : -0.2310
Centered cube (Jacoby rule) : -0.2186
Opponent owns cube : -0.3548
Win W(g) W(bg) L(g) L(bg) Equity (cubeful)
static: 0.456 0.244 0.014 0.318 0.019 (-0.168 (-0.219))
No double : -0.219
Double, pass : +1.000 (+1.219)
Double, take : -0.710 (-0.491)
Correct cube action: No double, beaver