Gaviota endgame tablebase probing¶

Gaviota tablebases provide WDL (win/draw/loss) and DTM (depth to mate) information for all endgame positions with up to 5 pieces. Positions with castling rights are not included.

chess.gaviota.open_tablebases(directory, libgtb=None, LibraryLoader=<ctypes.LibraryLoader object>)¶

Opens a collection of tablebases for probing.

First native access via the shared library libgtb is tried. You can optionally provide a specific library name or a library loader. The shared library has global state and caches, so only one instance can be open at a time.

Second pure Python probing code is tried.

class chess.gaviota.PythonTablebases(lzma)¶

Provides access to Gaviota tablebases using pure Python code.

open_directory(directory)¶: Loads .gtb.cp4 tables from a directory.

probe_dtm(board)¶

Probes for depth to mate information.

The absolute value is the number of half-moves until forced mate (or 0 in drawn positions). The value is positive if the side to move is winning, otherwise it is negative.

In the example position white to move will get mated in 10 half-moves:

>>> import chess
>>> import chess.gaviota
>>>
>>> with chess.gaviota.open_tablebases("data/gaviota") as tablebases:
...     board = chess.Board("8/8/8/8/8/8/8/K2kr3 w - - 0 1")
...     print(tablebases.probe_dtm(board))
...
-10

Raises:	`KeyError` (or specifically `chess.gaviota.MissingTableError`) if the probe fails. Use `get_dtm()` if you prefer to get `None` instead of an exception.

probe_wdl(board)¶

Probes for win/draw/loss-information.

Returns 1 if the side to move is winning, 0 if it is a draw, and -1 if the side to move is losing.

>>> import chess
>>> import chess.gaviota
>>>
>>> with chess.gaviota.open_tablebases("data/gaviota") as tablebases:
...     board = chess.Board("8/4k3/8/B7/8/8/8/4K3 w - - 0 1")
...     print(tablebases.probe_wdl(board))
...
0

Raises:	`KeyError` (or specifically `chess.gaviota.MissingTableError`) if the probe fails. Use `get_wdl()` if you prefer to get `None` instead of an exception.

close()¶: Closes all loaded tables.

backports.lzma¶

For Python versions before 3.3 you have to install backports.lzma in order to use the pure Python probing code.

sudo apt-get install liblzma-dev libpython2.7-dev
pip install backports.lzma

libgtb¶

For faster access you can build and install a shared library. Otherwise the pure Python probing code is used.

git clone https://github.com/michiguel/Gaviota-Tablebases.git
cd Gaviota-Tablebases
make
sudo make install

chess.gaviota.open_tablebases_native(directory, libgtb=None, LibraryLoader=<ctypes.LibraryLoader object>)¶

Opens a collection of tablebases for probing using libgtb.

In most cases open_tablebases() should be used. Use this function only if you do not want to downgrade to pure Python tablebase probing.

Raises:	`RuntimeError` or `OSError` when libgtb can not be used.

class chess.gaviota.NativeTablebases(libgtb)¶: Provides access to Gaviota tablebases via the shared library libgtb. Has the same interface as PythonTablebases.