Panterfish is a fork of sunfish, a simple, but strong chess engine, written in Python.
The simplest way to run panterfish is through the "fancy" terminal interface:
$ tools/fancy.py -cmd ./panterfish.py
Playing against ...
Do you want to be white or black? black
1 ♖ ♘ ♗ ♔ ♕ ♗ ♘ ♖
2 ♙ ♙ ♙ ♙ ♙ ♙ ♙ ♙
3
4
5
6
7 ♟ ♟ ♟ ♟ ♟ ♟ ♟ ♟
8 ♜ ♞ ♝ ♚ ♛ ♝ ♞ ♜
h g f e d c b a
Score: 23, nodes: 11752, nps: 13812, time: 0.9
My move: d4
1 ♖ ♘ ♗ ♔ ♕ ♗ ♘ ♖
2 ♙ ♙ ♙ ♙ ♙ ♙ ♙
3
4 ♙
5
6
7 ♟ ♟ ♟ ♟ ♟ ♟ ♟ ♟
8 ♜ ♞ ♝ ♚ ♛ ♝ ♞ ♜
h g f e d c b a
Your move (e.g. c6 or g8h6): Nf6
Note this requires the python-chess package. For a true minimalist experience, first we can "pack" panterfish into a compressed executable (less than 3KB!) and run it directly:
$ build/pack.sh panterfish.py packed.sh Total length: 2953 $ ./packed.sh go wtime 1000 btime 1000 winc 1000 binc 1000 info depth 1 score cp 0 pv d2d4 bestmove d2d4
(See the UCI specification for the full set of commands.)
It is also possible to run panterfish with a graphical interface, such as PyChess or Arena.
Finally you can play panterfish now on Lichess
- Built around the simple, but efficient MTD-bi search algorithm, also known as C*.
- Filled with classic "chess engine tricks" for simpler and faster code.
- Efficiently updatedable evaluation function through Piece Square Tables.
- Uses standard Python collections and data structures for clarity and efficiency.
panterfish supports all chess rules, except the 50 moves draw rule.
There are many ways in which you may try to make panterfish stronger. First you could change from a board representation to a mutable array and add a fast way to enumerate pieces. Then you could implement dedicated capture generation, check detection and check evasions. You could also move everything to bitboards, implement parts of the code in C or experiment with parallel search!
The other way to make panterfish stronger is to give it more knowledge of chess. The current evaluation function only uses piece square tables - it doesn't even distinguish between midgame and endgame. You can also experiment with more pruning - currently only null move is done - and extensions - currently none are used. Finally panterfish might benefit from a more advanced move ordering, MVV/LVA and SEE perhaps?
An easy way to get a strong panterfish is to run with with the PyPy Just-In-Time intepreter. In particular the python2.7 version of pypy gives a 250 ELO boost compared to the cpython (2 or 3) intepreters at fast time controls:
Rank Name Elo +/- Games Score Draws
1 pypy2.7 (7.1) 166 38 300 72.2% 19.7%
2 pypy3.6 (7.1) 47 35 300 56.7% 21.3%
3 python3.7 -97 36 300 36.3% 20.7%
4 python2.7 -109 35 300 34.8% 24.3%
The name panterfish actually refers to the Pygmy panterfish, which is among the very few fish to start with the letters 'Py'. The use of a fish is in the spirit of great engines such as Stockfish, Zappa and Rybka.
In terms of Heritage, panterfish borrows much more from Micro-Max by Geert Muller and PyChess.