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December 2018


Command-line for probing Syzygy tablebases


fathom - Command-line for probing Syzygy tablebases


fathom [--help] [--path=PATH] [--test] FEN


FEN The position (as a FEN string) to be probed.
--help Print this helpful message.
Set the tablebase PATH string.
--test Print the result only. Useful for scripts.


This program is a stand-alone Syzygy tablebase probe tool.
The program takes as input a FEN string representation of a chess position and outputs a PGN representation of the probe result.
In addition to the standard fields, the output PGN represents the following information:
- Result: "1-0" (white wins), "1/2-1/2" (draw), or "0-1" (black wins)
- The Win-Draw-Loss (WDL) value for the next move: "Win", "Draw",
"Loss", "CursedWin" (win but 50-move draw) or "BlessedLoss"
(loss but 50-move draw)
- The Distance-To-Zero (DTZ) value (in plys) for the next move
- WinningMoves: The list of all winning moves
- DrawingMoves: The list of all drawing moves
- LosingMoves: The list of all losing moves
The PGN contains a pseudo "principle variation" of Syzygy vs. Syzygy for the input position. Each PV move is rational with respect to preserving the WDL value. The PV does not represent the shortest mate nor the most natural human moves.


Fathom was written by basil <>. This manual page was written by Jose G. López <> for the Debian GNU/Linux project, but may be used by others. It was written with the assistance of help2man(1) and then edited slightly to clean it up.
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