Pystockfish

PyGot

Transcript

1. PyGotham 2014 Teaching Python to Play Chess August 17th, 2014 Jarret Petrillo, jarret.petrillo@gmail.com
2. If you can't solve a problem, there is an easier problem you can solve: find it - George Polya 1
3. How to get Python to play chess? 2
4. Solution 1: Statistical approach Download sci-kit learn Categorize positions according to king safety, pawn structure, and development Develop a choice model Use historical games by grand masters to callibrate model parameters Too complicated 3
5. Solution 2: Class-based approach Define a chess board as an 8x8 grid Implement a generic piece class Subclass the piece class to include rules for how each moves A chess game would then be a board and a collection of pieces A move would take one piece and place it somewhere else Still too complicated 4
6. The bully heurestic 5
7. Connect python to a piece of software that knows how to play chess 6
8. Making something easier to do is progress 7
9. Presentation overview Develop ease of use as a worthy project goal Describe bully heurestic as one type of solution Walk through pystockfish as an example of this approach in action 8
10. Has anyone published a package? 9
11. Pystockfish takes a package and makes doing one task easier Pystockfish builds off a class from the subprocess package Subprocess allows python to work with the input/output from a subroutine Stockfish runs at the terminal level 10
12. Subprocess allows Pyton to interact with any executable software 11
13. Good classes in action from flask import Flask app = Flask(__name__) app.config['DEBUG']=True if __name__ == '__main__': app.run() 12
14. Well-designed objects are easy to use 13
15. More good classes in action from webapp import db from models import User u = User(name="Jarret") db.session.add(u) db.session.commit() 14
16. Ease of use hides complexity Underneath the hood the sqlalchemy session object interacts with SQL Stores variables in a temporary state Saves objects to permanent database Handles synchronous requests 15
17. Ease of use is progress 16
18. Question of thinking depth motivated Pystockfish 17
19. Application in chess 18
20. Pystockfish problem statement Take two instances of the stockfish engine Set them to different thinking depths Have them play Record result Repeat 19
21. Programming problem statement Create two instances of the stockfish engine Set parameters Translate parameters into the language of stockfish Make a match between the two engines Have the first engine make a move Translate move into the language of stockfish and have the second engine move Repeat until one side wins or game is drawn Repeat with multiple engines 20
22. How to use stockfish from the terminal >>stockfish Stockfish 120212 by Tord Romstad, Marco Costalba, and Joona Kiiski ucinewgame position startpos moves e2e4 e7e5 go depth 15 info depth 1 seldepth 1 score cp 64 nodes 59 nps 2185 time 27 multipv 1 pv b1c3 info depth 2 seldepth 2 score cp 12 nodes 298 nps 11037 time 27 multipv 1 pv b1c3 b8c6 ... info depth 15 seldepth 22 score cp 56 nodes 1608006 nps 1472532 time 1092 multipv g1f3... bestmove g1f3 ponder g8f6 21
23. End use case >>from pystockfish import Engine >>deepthinker = Engine(depth=15) >>deepthinker.setposition(['e2e4','e7e5']) >>deepthinker.bestmove() 'g1f3' 22
24. Programming is connecting the dots 23
25. Challenges Stockfish understands only UCI protocol - TRANSLATION Bestmove function is not instantenous - SYNCHRONY Commands submitted in python but processed in terminal - STATE EQUALITY 24
26. Wrapping subprocess import subprocess class Engine(subprocess.Popen): def __init__(self, depth): subprocess.Popen.__init__(self, 'stockfish', universal_newlines=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE) self.depth = depth 25
27. Put function def put(self, command): self.stdin.write(command+'\n') 26
28. Isready function and the put/until model def isready(self): self.put('isready') last_line='' while True: text=self.stdout.readline().strip() if text=='readyok': return lastline lastline=text 27
29. Building more complex functions def newgame(self): self.put("ucinewgame") self.isready() def setposition(self, moves=[]): moveString=self._movelisttostr(moves) self.put("position startpos moves %s" % moveString) self.isready() 28
30. Bestmove function using the put/until model def bestmove(self): last_line = "" self.put('go depth %s'%self.depth) while True: text = self.stdout.readline().strip() split_text = text.split(' ') if split_text[0]=='bestmove': return {'move': split_text[1], 'ponder': split_text[3], 'info': last_line } last_line = text 29
31. Publishing your work 30
32. Put something where those who need it can find it 31
33. If it's not easy to find it doesn't exist PyPI is one-stop pacakge repository Makes distribution straightforward using setuptools Allows users to install software with pip command Creates a weblink that can be shared 32
34. Creating a package is a commitment to maintain it 33
35. Innovation one small step at a time A problem solved makes room for the next one Making it easier to do something is an achievement If it's public others can build off it 34
36. Flask showcases this process in action 35
37. Thank you 36