tempate / achillees

A readable chess engine written in C.

Achillees

This project is an attempt at making a readable and accessible chess engine. It's written in plain C and it currently uses the GPLv3+ license. The command help will show you the list of human-friendly commands. You can also set it to UCI mode with the command uci.

All comments and feedback are appreciated. Feel free to join us at ##chessprogramming on Freenode IRC and share your thoughts.

You are also free to challenge it at Lichess.

Features

The project is under active development and new features will come shortly.

Move generation

• Plain magic bitboards
• Legal move generation

Evaluation

• Material count
• Piece-Square tables

Search

• AlphaBeta Pruning

• Move ordering

• Transposition Table

• Time management

• Quiescence search

• Check extensions

• Late move reduction

• Aspiration windows

• Null window search

• Internal Iterative Deepening

• Pruning

  • Razoring
  • Delta pruning
  • Null move pruning
  • Futility pruning
  • Reverse futility pruning
  • Late move pruning

Running the code

You can get the code running by following three simple steps:

1. Download the code

git clone https://github.com/Tempate/Achillees

2. Type the command:

make release

3. An executable should now appear inside your bin folder, you can run it by doing:

./Achillees

Credits

Special thanks to the chessprogramming wiki, as most of the knowledge needed came from reading through it; to ROCE, without which it would have taken ages to pass perft; and to Daily Chess for their fantastic guide.

I also feel the need to thank everyone on ##chessprogramming on Freenode IRC for their support, encouragement, and exhaustive help.

achillees's Issues

new version ?

I read at "Features" :
The project is under active development and new features will come shortly.

Are you still planning to work on Achillees ?

The aspiration window condition is wrong(?)

Hi, I recently discovered this engine and notice that this line is wrong? https://github.com/Tempate/Achillees/blob/master/src/search.c#L54, it should be like this? https://web.archive.org/web/20071031095918/http://www.brucemo.com/compchess/programming/aspiration.htm

Made android armv7-neon version

This version in android I added math_neon.h runfast commands to the source. It is very fast and kicks the Sasha engine butt.

Illegal move

Here is the game:

[Round "2"]
[White "Achillees"]
[Black "zahak_next"]
[Result "0-1"]
[ECO "B50"]
[GameDuration "00:03:37"]
[GameEndTime "2021-04-21T13:18:41.891 EDT"]
[GameStartTime "2021-04-21T13:15:04.512 EDT"]
[Opening "Sicilian"]
[PlyCount "116"]
[Termination "illegal move"]
[TimeControl "60+1"]

1. e4 {book} c5 {book} 2. Nf3 {book} d6 {book} 3. Nc3 {+0.40/13 3.2s}
Nf6 {-0.70/12 3.0s} 4. d4 {+0.40/13 3.1s} cxd4 {-0.54/12 2.9s}
5. Qxd4 {+0.37/12 3.1s} Bg4 {-0.74/11 2.9s} 6. h3 {+0.43/12 3.0s}
Bxf3 {-0.30/13 2.8s} 7. gxf3 {+0.32/13 2.9s} e5 {-0.40/12 2.7s}
8. Qa4+ {+0.55/13 2.8s} Nbd7 {-0.55/12 2.7s} 9. Qb5 {+0.48/12 2.8s}
Qc7 {-0.18/12 2.6s} 10. Nd5 {+0.54/14 2.7s} Nxd5 {+0.05/13 2.6s}
11. exd5 {+0.56/14 2.6s} a6 {+0.79/12 2.5s} 12. Qb4 {+0.51/13 2.6s}
Be7 {+0.78/12 2.5s} 13. Rg1 {+0.50/12 2.5s} a5 {+0.55/11 2.4s}
14. Qa4 {+0.71/13 2.5s} g6 {+0.35/12 2.4s} 15. Bh6 {+0.88/13 2.4s}
O-O-O {+0.26/13 2.3s} 16. Bb5 {+1.01/11 2.4s} Nc5 {+0.30/12 2.3s}
17. Qc4 {+1.08/13 2.3s} Kb8 {+0.26/13 2.2s} 18. c3 {+1.10/12 2.3s}
Qc8 {+0.74/12 2.2s} 19. Rg3 {+1.31/13 2.2s} Qf5 {+0.74/11 2.2s}
20. b4 {+1.29/14 2.2s} Nd7 {+0.62/12 2.1s} 21. bxa5 {+1.86/13 2.1s}
Nc5 {+0.06/11 2.1s} 22. Qg4 {+1.69/12 2.1s} Qc2 {+0.72/13 2.0s}
23. Qb4 {+1.60/13 2.0s} Ka8 {+0.60/12 2.0s} 24. a3 {+1.97/12 2.0s}
Bh4 {+1.28/11 2.0s} 25. Rc1 {+2.49/15 2.0s} Qb3 {-0.56/13 1.9s}
26. Rg4 {+2.48/14 1.9s} Be7 {-0.55/12 1.9s} 27. Bc4 {+2.33/14 1.9s}
Qa4 {-0.21/14 1.9s} 28. Bb5 {+2.46/13 1.9s} Qb3 {-0.47/14 1.9s}
29. Bc4 {+2.31/13 1.8s} Qa4 {-0.10/13 1.8s} 30. Qxa4 {+2.31/13 1.8s}
Nxa4 {-0.66/13 1.8s} 31. Bf1 {+2.27/13 1.8s} Nc5 {-0.28/13 1.8s}
32. Rb1 {+1.89/12 1.7s} Rc8 {0.00/12 1.7s} 33. c4 {+2.03/12 1.7s}
Bd8 {+0.27/10 1.7s} 34. Rb5 {+1.98/14 1.7s} f5 {+0.24/11 1.7s}
35. Rg1 {+1.79/13 1.7s} f4 {-0.08/12 1.7s} 36. Kd2 {+1.88/13 1.6s}
Kb8 {-0.17/12 1.6s} 37. Kc3 {+1.82/12 1.6s} Na6 {+0.18/12 1.6s}
38. Kb3 {+1.98/13 1.6s} Nc7 {0.00/14 1.6s} 39. Rb6 {+1.39/15 1.6s}
Ne8 {0.00/14 1.6s} 40. Rb5 {+1.24/15 1.5s} Nc7 {0.00/15 1.6s}
41. Rb6 {+1.19/15 1.5s} Ne8 {0.00/16 1.5s} 42. Rb4 {+1.07/14 1.5s}
Bxa5 {+0.81/15 1.5s} 43. Rb5 {+1.05/14 1.5s} Be1 {+1.04/15 1.5s}
44. Rg2 {+0.86/15 1.5s} Nc7 {+0.94/14 1.5s} 45. Rb6 {+0.85/15 1.5s}
Rhd8 {+0.81/13 1.5s} 46. Ka2 {+0.86/14 1.4s} Bc3 {+0.79/13 1.5s}
47. Rb1 {+0.78/13 1.4s} Bd4 {+0.99/12 1.4s} 48. Bd3 {+0.79/13 1.4s}
Na8 {+1.00/12 1.4s} 49. Rb5 {+0.76/13 1.4s} Nb6 {+1.24/13 1.4s}
50. Kb3 {+0.78/13 1.4s} Rc7 {+1.39/14 1.4s} 51. Be2 {+0.37/14 1.4s}
Rdc8 {+1.35/13 1.4s} 52. Rb4 {0.00/15 1.3s} Bc5 {+1.33/12 1.4s}
53. Rb5 {0.00/15 1.3s} Bd4 {+1.39/14 1.4s} 54. Rb4 {0.00/15 1.3s}
Ka8 {+1.27/14 1.4s} 55. Bf1 {+0.47/13 1.3s} Bc5 {+1.36/13 1.3s}
56. Rb5 {0.00/15 1.3s} Bd4 {+1.34/13 1.3s} 57. Rb4 {0.00/15 1.3s}
Bc5 {+1.33/13 1.3s} 58. Rb5 {0.00/15 1.3s}
Ka7 {+1.29/13 1.3s, White makes an illegal move: b6c4} 0-1

Unfortunately I don't have logs, but it looks like the issue is with declaring draws too early?