Chess puzzle maker

This is a command-line program that creates chess puzzles from positions with clear sequences of best moves.
It looks for positions where a player can:

• Checkmate the opponent in a forced sequence
• Convert a position into a material advantage
• Equalize a losing position

Give it a PGN with any number of games or positions and it will look for positions to convert into puzzles:

./make_puzzles.py --pgn games.pgn

Or give it a position (FEN) and it will try to create a puzzle:

./make_puzzles.py --fen "6rr/1k3p2/1pb1p1np/p1p1P2R/2P3R1/2P1B3/P1BK1PP1/8 b - - 5 26"

For a list of options:

./make_puzzles.py -h

Requirements

This requires Python 3 and a UCI-compatible chess engine such as Stockfish.

Install the required python libraries:

pip3 install -r requirements.txt

Make sure you have a version of Stockfish available in your $PATH or local directory:

• You can install a Stockfish binary using Homebrew if you're on macOS (brew install stockfish)
• Or install an old version of Stockfish using apt if you're on Ubuntu Linux (sudo apt install stockfish)
• Or download an official Stockfish release from the Stockfish website
• Or run ./build-stockfish.sh to compile the latest official Stockfish development build
• Or run inv update-stockfish to get the latest multi-variant Stockfish fork used by Lichess

Creating puzzles

Created puzzles are printed in PGN format to standard output
while errors and log messages are printed to standard error.

If you want to write created puzzles to a file, redirect standard output:

./make_puzzles.py --pgn games.pgn >> puzzles.pgn

How it works

It scans the moves of a game for mistakes, represented by large swings in position evaluation.

<img src="https://user-images.githubusercontent.com/208617/70076652-3af78380-15cd-11ea-969b-217789c5401b.png" width=340 />

For each of these positions, it looks for move sequences where the player can make one clear best move.

<img src="https://user-images.githubusercontent.com/208617/70076756-742ff380-15cd-11ea-828a-44f0ed12b78d.png" width=340 />

If it finds that the position could become a puzzle, it will output the puzzle as a PGN.

Example PGN output

[FEN "6rr/1k3p2/1pb1p1np/p1p1P2R/2P3R1/2P1B3/P1BK1PP1/8 b - - 5 26"]
[PuzzleCategory "Material"]
[PuzzleEngine "Stockfish 2018-11-29 64 Multi-Variant"]
[PuzzleWinner "Black"]
[SetUp "1"]

26... Nxe5   { Nxe5  [-1.68] }
27.   Rxg8   { Rxg8  [-1.66] Rgh4 [-2.51]  Re4  [-3.51] }
27... Nxc4+  { Nxc4+ [-1.78] Rxg8 [ 3.82]  Nf3+ [ 4.79] }
28.   Kd3    { Kd3   [-1.55] Ke2  [-1.83]  Kd1  [-2.85] }
28... Nb2+   { Nb2+  [-1.78] Rxg8 [ 2.11]  Ne5+ [ 3.44] }
29.   Ke2    { Kd2   [-1.64] Ke2  [-1.74]               }

Each move in the puzzle is annotated with the best 3 candidate moves
considered by the chess engine.

Example commands

To scan a PGN for positions that might be candidate puzzles without
investigating any of the positions:

./make_puzzles.py --scan-only --pgn games.pgn

To start at the n-th PGN in a PGN file with lots of games:

./make_puzzles.py --start-index 1234 --pgn games.pgn

To fetch a Lichess game and save it as a PGN:

inv fetch-lichess -g 12345

To fetch all games from a Lichess tournament and save the games to PGN:

inv fetch-lichess -t 67890

You can run the whole test suite with:

inv test

Acknowledgements

This program is based on:

• Python-Puzzle-Creator by @clarkerubber
• pgn-tactics-generator by @vitogit