1. "Intelligent" CS 5 An object is structured data that is alive, responsible, and intelligent. Sound too friendly? This week’s objects and classes will be just the opposite... X to move. Is there a way to win? | | | | | | | |X| | | | | |X| |X|O| | | |X|O|O|O|X|O| | --------------- 0 1 2 3 4 5 6 Hw 10 due 11/15 EXAM 2 Mon/Tue

2. def tomorrow(self): """Changes the calling object so that it represents one calendar day after the date it originally represented. """ if self.month in [1,3,5,7,8,10] and self.day == 31: self.day = 0 self.month += 1 elif self.month in [4,6,9,11] and self.day == 30: self.day = 0 self.month += 1 elif self.month == 2: if self.isLeapYear() and self.day == 29: self.day = 0 self.month += 1 elif (self.isLeapYear() == False) and self.day == 28: self.day = 0 self.month += 1 elif self.month == 12 and self.day == 31: self.day = 0 self.month = 1 self.year += 1 self.day += 1 Coding Style

3. def tomorrow(self): """Changes the calling object so that it represents one calendar day after the date it originally represented. """ DIM = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31] if self.isLeapYear() == True: DIM = [0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31] self.day += 1 if self.day > DIM[self.month]: self.day = 1 self.month += 1 if self.month > 12: self.month = 1 self.year += 1 else: self.day += 1 if self.day > DIM[self.month]: self.day = 1 self.month += 1 if self.month > 12: self.month = 1 self.year += 1 Better Style, But...

4. def tomorrow(self): """Changes the calling object so that it represents one calendar day after the date it originally represented. """ DIM = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31] if self.isLeapYear(): DIM[2] = 29 self.day += 1 if self.day > DIM[self.month]: self.day = 1 self.month += 1 if self.month > 12: self.month = 1 self.year += 1 An Elegant Solution

5. isBefore/isAfter def isBefore(self, d2): """ Returns true if self is before d2 """ if self.year < d2.year: return True if self.month < d2.month and self.year == d2.year: return True if self.day < d2.day and d2.month == self.month and \ self.year == d2.year: return True return False def isAfter(self, d2): """ Returns true if self is after d2 """ if self.year > d2.year: return True if self.month > d2.month and self.year == d2.year: return True if self.day > d2.day and d2.month == self.month and \ self.year == d2.year: return True return False

6. An Elegant Solution def isBefore(self, d2): """ Returns true if self is before d2 """ if self.year < d2.year: return True if self.month < d2.month and self.year == d2.year: return True if self.day < d2.day and d2.month == self.month and \ self.year == d2.year: return True return False def isAfter(self, d2): """ Returns true if self is after d2 """ return d2.isBefore(self)

7. Another Elegant Solution def isBefore(self, d2): """ Returns true if self is before d2 """ return ([self.year, self.month, self.day] < [d2.year, d2.month, d2.day]) def isAfter(self, d2): """ Returns true if self is after d2 """ return d2.isBefore(self)

8. diff def diff( self, d2 ): """ Returns the number of days between self and d2 """ dcopy = self.copy() difference = 0 if dcopy.isBefore(d2) == True: while dcopy.isBefore(d2) == True: dcopy.tomorrow() difference -= 1 else: while dcopy.isAfter(d2): dcopy.yesterday() difference += 1 return difference

9. An Elegant Solution def diff( self, d2 ): """ Returns the number of days between self and d2 """ dcopy = self.copy() difference = 0 while dcopy.isBefore(d2): dcopy.tomorrow() difference -= 1 while dcopy.isAfter(d2): dcopy.yesterday() difference += 1 return difference

10. Aargh! Python has no Connect-four datatype… | | | | | | | |X| | | | | |X| |X|O| | | |X|O|O|O|X| |O| --------------- 0 1 2 3 4 5 6 Can I see a demo? … but we can correct that!

11. Designing classes 1) What data? (Data Members) 2) What are objects' crucial capabilities? (Methods) Not limited to 7x6!

12. Connect Four: the object b Board b int width str data list str data int height What is the name of the method that will construct this data?

13. Connect Four: constructor class Board: """ a datatype representing a C4 board with an arbitrary number of rows and cols """ def __init__( self, width, height ): """ the constructor for objects of type Board """ self.width = width self.height = height self.data = [] # this will be the board for row in range( 6 ): boardRow = [] for col in range( 7 ): boardRow += [' '] # add a space to this row self.data += [boardRow] Bad magic?

14. Connect Four: the object b Board b int width str data list str int height | | | | | | | |X| | | | | |X| |X|O| | | |X|O|O|O|X| |O| --------------- 0 1 2 3 4 5 6 What is the name of the method that will print this data?

15. def __repr__(self): """ this method returns a string representation for an object of type Board """ s = '' for row in range( 6 ): s += '|' for col in range( 7 ): s += self.data[row][col] + '|' s += '\n' return s Connect Four: __repr__ To change? To add? which row is row 0, row 1, and so on?

16. "Quiz" class Board: def allowsMove(self, col): def addMove(self, col, ox): for row in range( self.height ): if self.data[row][col] != ' ': self.data[row-1][col] = ox self.data[self.height-1][col] = ox Step through this addMove method. What is each line doing? How many problems are there? a C4 board col # 'X' or 'O' Write allowsMove to return True if col is a valid move; False otherwise. NAME:

17. C4 Board class: methods __init__( self, width, height ) allowsMove( self, col ) __repr__( self ) addMove( self, col, ox ) isFull( self ) winsFor( self, ox ) the “constructor” checks if allowed places a checker outputs a string checks if any space is left checks if a player has won hostGame( self ) play (person vs. person)! delMove( self, col ) removes a checker Which of these will require the most thought?

18. winsFor( self, ox ) Thoughts? X O b b.winsFor( 'X' ) or 'O' corner cases?

19. Two-player games have been a key focus of AI as long as computers have been around… Strategic thinking == intelligence ? In 1945, Alan Turing predicted that computers would be better chess players than people in ~ 50 years… and thus would have achieved intelligence. Alan Turing memorial Manchester, England

20. Two-player games have been a key focus of AI as long as computers have been around… Strategic thinking == intelligence ? … humans and computers have different relative strengths in these games. humans computers good at evaluating the strength of a board for a player good at looking ahead in the game to find winning combinations of moves

21. How humans play games… - experts could reconstruct these perfectly - novice players did far worse… An experiment (by A. deGroot) was performed in which chess positions were shown to novice and expert players…

22. How humans play games… - experts could reconstruct these perfectly - novice players did far worse… Random chess positions (not legal ones) were then shown to the two groups - experts and novices did equally well (badly) at reconstructing them! An experiment (by A. deGroot) was performed in which chess positions were shown to novice and expert players…

23. Two-player games have been a key focus of AI as long as computers have been around… Strategic thinking == intelligence ? humans computers good at evaluating the strength of a board for a player good at looking ahead in the game to find winning combinations of moves … humans and computers have different relative strengths in these games. building an AI chess player emulating a human by evaluating a board position

24. The Player class Player pForX Details (data and methods) What data and methods are needed to construct and implement a Player object? Let's see a demo!

25. string ox Picture of a Player object Player pForX __init__(self, ox, tbt, ply) string tbt __repr__(self) scoreBoard(self, b) scoresFor(self, b) tiebreakMove(self, scores) nextMove(self, b) oppCh(self) 'X' 'LEFT' int ply 3 DATA METHODS tiebreakType checker, O or X

26. scoreBoard ‘X’ ‘O’ Assigns a score to any board, b 100.0 50.00.0 A simple system: for a win for a lossfor anything else Score for

27. scoreBoard Assigns a score to any board, b 100.0 50.0 A simple system: for a winillegal board for anything else scoreBoard(self, b) Implementation ideas… What methods that already exist will come in handy? This doesn't seem to be looking very far ahead ! How can there be no 'X' or 'O' input? What class is this method in? 0.0 for a loss

28. Looking further ahead… scoreBoard looks ahead 0 moves The "Zen" approach -- we are excellent at this! If you look one move ahead, how many possibilities are there to consider? 0-ply 1-ply A 1-ply lookahead player will "see" an impending victory. to move… A score for each column…? score

29. Looking further ahead… scoreBoard looks ahead 0 moves The "Zen" approach -- we are excellent at this! If you look one move ahead, how many possibilities are there to consider? 0-ply A 2-ply lookahead player will also "see" an opponent's impending victory. to move… What about 3-ply? 2-ply 1-ply score

30. Looking further ahead… scoreBoard looks ahead 0 moves The "Zen" approach -- we are excellent at this! If you look one move ahead, how many possibilities are there to consider? 0-ply 1-ply scoresFor( self, b ) returns a LIST of scores, one for each column you can choose to move next… 2-ply

31. |O| | | | | | | |X| | | |O| |X| |O| | | |X|O|X| |X| | | |O|O|X| |X| |X| |X|O|O| |X| |O|O|O|X|X| --------------- 0 1 2 3 4 5 6 | | | | | | |O| | | | | | | |X| |X| |X|O| | |O| |X|O|O|X| |X|X| |X|O|O|O| |O|X| --------------- 0 1 2 3 4 5 6 It is O’s move. What scores does a 1-ply lookahead for O assign to each move? col 0col 1col 2col 3col 4col 5col 6 It is X’s move. What scores does a 2-ply lookahead for X assign to each move? col 0col 1col 2col 3col 4col 5col 6 Which change at 3-ply? Which change at 2-ply? Example 1-ply and 2-ply lookahead scores

32. b 0-ply scores for O: col 0col 1col 2col 3col 4col 5col 6 1-ply scores for O: col 0col 1col 2col 3col 4col 5col 6 2-ply scores for O: col 0col 1col 2col 3col 4col 5col 6 3-ply scores for O: col 0col 1col 2col 3col 4col 5col 6 Practice ‘X’ ‘O’

33. 0-ply scores for O: col 0col 1col 2col 3col 4col 5col 6 1-ply scores for O: col 0col 1col 2col 3col 4col 5col 6 2-ply scores for O: col 0col 1col 2col 3col 4col 5col 6 3-ply scores for O: col 0col 1col 2col 3col 4col 5col 6 Solutions 50 10050 0 0 100 0 0 0 050 100 00 b ‘X’ ‘O’

34. 500 1200 2000 2800 Computer Chess early programs ~ 1960’s Computers cut their teeth playing chess… Ranking beginner amateur world ranked world champion MacHack ( 1100 ) ~ 1967 MIT Deep Thought ~ 1989 Carnegie Mellon Slate ( 2070 ) ~ 1970’s Northwestern Deep Blue ~ 1996 IBM Deep Blue rematch ~ 1997 IBM 100’s of moves/sec 10,000’s of moves/sec 1,000,000’s moves/sec 3,500,000 moves/sec Deep Fritz: 2002 X3D Fritz: 2003 Hydra: 2006 200,000,000 moves/sec first paper: 1950 What is Hydra's chess rating?

35. Games’ Branching Factors Branching Factor Estimates for different two-player games Tic-tac-toe 4 Connect Four 7 Checkers 10 Othello 30 Chess 40 Go 300 On average, there are fewer than 40 possible moves that a chess player can make from any board configuration… 0 Ply 1 Ply 2 Ply Hydra at home in the United Arab Emirates… Hydra looks ahead 18 ply !

36. Games’ Branching Factors Branching Factor Estimates for different two-player games Tic-tac-toe 4 Connect Four 7 Checkers 10 Othello 30 Chess 40 Go 300 1 Ply 2 Ply Boundaries for qualitatively different games… 0 Ply

37. Games’ Branching Factors Branching Factor Estimates for different two-player games Tic-tac-toe 4 Connect Four 7 Checkers 10 Othello 30 Chess 40 Go 300 “solved” games computer-dominated human-dominated 1 Ply 2 Ply 0 Ply Progress

39. ‘X’ ‘O’ new‘X’ Col 6 Col 5 Col 4 Col 3 Col 2 Col 1 Col 0 b scoresFor each column (1) For each possible move (2) Add it to the board

40. ‘X’ ‘O’ new‘X’ Col 6 Col 5 Col 4 Col 3 Col 2 Col 1 Col 0 b (1) For each possible move (2) Add it to the board (3) Ask OPPONENT to score each board At what ply? 0.0 50.0 0.0 50.0 0.0 scoresFor each column

41. ‘X’ ‘O’ new‘X’ Col 6 Col 5 Col 4 Col 3 Col 2 Col 1 Col 0 b (1) For each possible move (2) Add it to the board (3) Ask OPPONENT to score each board (4) Take the opponent's MAX 0.0 50.0 0.0 50.0 0.0 What to assign for a score? scoresFor each column 50.0

42. scoresFor def scoresFor(self, b): (1) For each possible move (2) Add it to the board (3) Ask OPPONENT to score each board - at ? ply (4) the score is 100-max

43. Write tiebreakMove to return the leftmost best score inside the list scores def tiebreakMove(self, scores): if self.tbt == 'LEFT': How would 'RANDOM' and 'RIGHT' work differently?

44. hw11 this week Problem 3: A Connect Four Player … Extra: scoreBoard4Tourney and a CS 5 C4 round-robin http://www.stanford.edu/~ccecka/research/C4.html Using more scores than 0, 50, and 100 ! Problem 2: A Connect Four Board … don't give this board a 50.0 !

45. “Quiz” Names: |O| | | | | | | |X| | | |O| |X| |O| | | |X|O|X| |X| | | |O|O|X| |X| |X| |X|O|O| |X| |O|O|O|X|X| --------------- 0 1 2 3 4 5 6 | | | | | | |O| | | | | | | |X| |X| |X|O| | |O| |X|O|O|X| |X|X| |X|O|O|O| |O|X| --------------- 0 1 2 3 4 5 6 It is O’s move. What scores does a 1-ply lookahead for O assign to each move? col 0col 1col 2col 3col 4col 5col 6 It is X’s move. What scores does a 2-ply lookahead for X assign to each move? col 0col 1col 2col 3col 4col 5col 6 be careful! 1005010050 10050 100 00050 0 Which change at 2-ply? 00 Which change at 3-ply? 0

46. |O| | | | | | | |X| | | |O| |X| |O| | | |X|O|X| |X| | | |O|O|X| |X| |X| |X|O|O| |X| |O|O|O|X|X| --------------- 0 1 2 3 4 5 6 It is O’s move. What scores does a 1-ply lookahead for O assign to each move? col 0col 1col 2col 3col 4col 5col 6 Which change at 2-ply?

47. Looking further ahead … 0 ply: 2 ply:3 ply: Zen choice of move: here and now | | | | |O| | | | | | | |X| | | | | | | |X|O|O| | |X| | |O|X|X|O|X|O| | --------------- 0 1 2 3 4 5 6 | | | | | | | | |X| | | | | | | |O|O| | | |X|X| |X|O| | |O|X|O| |O|X| | --------------- 0 1 2 3 4 5 6 (1) Player will win (2) Player will avoid losing (3) Player will set up a win by forcing the opponent to avoid losing X ’s move X ‘s move 1 ply: | | | | | |O|X| | | | | |O|X|X|X| |O|O| --------------- 0 1 2 3 4 5 6 X ’s move

48. ‘X’ ‘O’ new‘X’ Col 6 Col 5 Col 4 Col 3 Col 2 Col 1 Col 0 b Choosing the best move (1) For each possible move (2) Add it to the board (3) Ask OPPONENT to score each board - ply? (4) Reverse the scores 100.0 50.0 100.0 50.0 100.0

49. ‘X’ ‘O’ new‘X’ Col 6 Col 5 Col 4 Col 3 Col 2 Col 1 Col 0 b Choosing the best move 100.0 50.0 100.0 50.0 100.0 (1) For each possible move (2) Add it to the board (3) Ask OPPONENT to score each board - ply? (4) Reverse the scores (5) Find one max - that's it!

50. Connect Four | | | | | | | |X| | | | | |X| |X|O| | | |X|O|O|O|X| |O| --------------- 0 1 2 3 4 5 6 Suppose our Board class's 2d list of lists is named self.data. What is the name of this single spot? For your convenience, the creators of Python’s library have included a Board class that can represent any size of Connect Four board... !

51. Connect Four: the object b This is true for sufficiently broad definitions of “the creators of Python’s library”... Board b def addMove(self, col, player) int NROWS int NCOLS def allowsMove(self, col) char data list char def winsFor(self, player) data members methods What is player ?

52. Connect Four: the object b This is true for sufficiently broad definitions of “the creators of Python’s library”... Board b def addMove(self, col, player) int NROWS int NCOLS def allowsMove(self, col) char data list char def winsFor(self, player) data members methods Which methods will alter b ? Which leave it alone?

53. Connect Four: Board Starting code for the Board class class Board: def __init__( self, numRows, numCols ): """ our Board's constructor """ self.NROWS = numRows self.NCOLS = numCols self.data = [] for r in range(self.NROWS): onerow = [' ']*self.NCOLS self.data += [onerow] def __repr__(self): """ thoughts? """ look familiar?

54. Connect Four: Board class Board: def __init__( self, numRows, numCols ): """ our Board's constructor """ self.NROWS = numRows self.NCOLS = numCols self.data = [] for r in range(self.NR): onerow = [' ']*self.NC self.data += [onerow] def __repr__(self): """ thoughts? """ s = '\n' for r in range(self.NROWS): s += '|' for c in range(self.NCOLS): s += self.data[r][c] + '|' return s look familiar? a bit more to go !

55. Problem 2 class Board __init__ allowsMove __repr__ addMove isFull winsFor the “constructor” checks if allowed places a checker outputs to screen checks if space left checks if a player has won Hw11 Pr2: Connect Four Board hostGame play! What's trickiest here?

56. Problem 2 class Board __init__ allowsMove __repr__ addMove isFull winsFor the “constructor” checks if allowed places a checker outputs to screen checks if space left checks if a player has won Hw11 Pr2: Connect Four Board hostGame play! What's trickiest here?

57. What's wrong here? | | | | | | | |O|O| | | |X|X| |O|X|X|X| |X|O|O|O|O|X|X| --------------- 0 1 2 3 4 5 6 def winsForHoriz(self, player): inarow = 0 for r in range(self.NROWS): for c in range(self.NCOLS): if self.data[r][c] == player: inarow += 1 else: inarow = 0 if inarow == 4: return True return False

58. Strategies? horizontals verticals diagonals ?? | | | | | | | |O|O| | | |X|X| |O|X|X|X| |X|O|O|O|O|X|X| --------------- 0 1 2 3 4 5 6

59. “Quiz” class Board { # __init__ and __repr__ methods here… # 3 data members: # self.NR == number of rows # self.NC == number of cols # self.data == the 2d list of lists of chars def mysteryMethod(self, col, ox): r = 0 while r < self.NR and self.data[r][col] == ' ': r += 1 self.data[r-1][col] = ox def allowsMove(self, col): } Briefly, what is each line of the mysteryMethod doing? Which method is it? Write allowsMove to return whether the input col is a valid column to move. ( True or False ) 1 2 3 Could it go wrong?

60. Problem 2 class Board __init__ allowsMove __repr__ addMove isFull winsFor the “constructor” checks if allowed places a checker outputs to screen checks if space left checks if a player has won Hw11 Pr2: Connect Four Board hostGame play! What's trickiest here?

61. Problem 2 class Board __init__ allowsMove __repr__ addMove isFull winsFor the “constructor” checks if allowed places a checker outputs to screen checks if space left checks if a player has won Hw11 Pr2: Connect Four Board hostGame play! What's trickiest here?

62. Strategies? horizontals verticals diagonals ?? | | | | | | | |X| | | | | |X| |X|O| | | |X|O|O|O|O| |O| --------------- 0 1 2 3 4 5 6