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Transcript of "Intelligent" CS 5 An object is structured data that is alive, responsible, and intelligent. Sound...
"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 11/15EXAM 2Mon/Tue
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
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...
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
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
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)
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)
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
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
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!
Designing classes
1) What data? (Data Members)
2) What are objects' crucial capabilities? (Methods)
Not limited to 7x6!
Connect Four: the object b
Boardb
intwidthstr str str
str str str
str str str
datalist str
str
str
data
intheight
What is the name of the method that will construct this data?
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?
Connect Four: the object b
Boardb
intwidthstr str str
str str str
str str str
datalist str
str
str
intheight
| | | | | | | || | | | | | | || | | | | | | || | | |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?
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?
"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:
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?
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
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.
humanscomputers
good at evaluating the strength of a board for a player
good at looking ahead in the game to find
winning combinations of moves
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…
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…
Two-player games have been a key focus of AI as long as computers have been around…
Strategic thinking == intelligence?
humanscomputers
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 playeremulating a human by
evaluating a board position
The Player class
PlayerpForX
Details(data and methods)
What data and methods are needed to construct and implement a Player object?
Let's see a demo!
stringox
Picture of a Player object
Player
PlayerpForX
__init__(self, ox, tbt, ply)
stringtbt
__repr__(self)
scoreBoard(self, b)
scoresFor(self, b)
tiebreakMove(self, scores)
nextMove(self, b)
oppCh(self)
'X' 'LEFT'intply
3
DATA
METHODS
tiebreakTypechecker, O or X
scoreBoard ‘X’‘O’
Assigns a score to any board, b
100.0 50.0 0.0A simple system:for a win for a lossfor anything else
Score for Score for
Score for Score for
scoreBoard
Assigns a score to any board, b
100.0 50.0 -1.0A simple system:for a win illegal boardfor 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?
0.0for a loss
Looking further ahead…
scoreBoard looks ahead 0 movesThe "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
Looking further ahead…
scoreBoard looks ahead 0 movesThe "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
score
Looking further ahead…
scoreBoard looks ahead 0 movesThe "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
|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|| | | | | | |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 0 col 1 col 2 col 3 col 4 col 5 col 6
It is X’s move. What scores does a 2-ply lookahead for X assign to each move?
col 0 col 1 col 2 col 3 col 4 col 5 col 6
Which change at 3-ply?
Which change at 2-ply?
Example 1-ply and 2-ply lookahead scores
b
0-ply scores for O:col 0 col 1 col 2 col 3 col 4 col 5 col 6
1-ply scores for O:col 0 col 1 col 2 col 3 col 4 col 5 col 6
2-ply scores for O:col 0 col 1 col 2 col 3 col 4 col 5 col 6
3-ply scores for O:col 0 col 1 col 2 col 3 col 4 col 5 col 6
Practice ‘X’‘O’
0-ply scores for O:col 0 col 1 col 2 col 3 col 4 col 5 col 6
1-ply scores for O:col 0 col 1 col 2 col 3 col 4 col 5 col 6
2-ply scores for O:col 0 col 1 col 2 col 3 col 4 col 5 col 6
3-ply scores for O:col 0 col 1 col 2 col 3 col 4 col 5 col 6
Solutions
-1
-1
-1
-1
50 50 50 50 50 50
50 50 100
50 50 50
0
0
100
100
0
0
0 0 50
100
00
b ‘X’‘O’
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/secDeep Fritz: 2002X3D Fritz: 2003 Hydra: 2006
200,000,000 moves/sec
first paper: 1950
What is Hydra's chess rating?
Games’ Branching Factors
Branching Factor Estimatesfor 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 !
Games’ Branching Factors
Branching Factor Estimatesfor 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
Games’ Branching Factors
Branching Factor Estimatesfor 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
‘X’‘O’new‘X’
Col 6
Col 5
Col 4Col 3Col 2
Col 1
Col 0
b
scoresFor each column
(1) For each possible move
(2) Add it to the board
‘X’‘O’new‘X’
Col 6
Col 5
Col 4Col 3Col 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
50.0
0.00.0
50.0
0.0
scoresFor each column
‘X’‘O’new‘X’
Col 6
Col 5
Col 4Col 3Col 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
0.00.0
50.0
0.0
What to assign for a score?
scoresFor each column
50.0
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
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?
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 !
“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|| | | | | | |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 0 col 1 col 2 col 3 col 4 col 5 col 6
It is X’s move. What scores does a 2-ply lookahead for X assign to each move?
col 0 col 1 col 2 col 3 col 4 col 5 col 6
be careful!
-1 100
50 100
50 100
50
100
0 0 0 50 0 -1
Which change at 2-ply? 0 0
Which change at 3-ply?0
|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 0 col 1 col 2 col 3 col 4 col 5 col 6
Which change at 2-ply?
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
‘X’‘O’new‘X’
Col 6
Col 5
Col 4Col 3Col 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
50.0
100.0100.0
50.0
100.0
‘X’‘O’new‘X’
Col 6
Col 5
Col 4Col 3Col 2
Col 1
Col 0
b
Choosing the best move
100.0
50.0
50.0
100.0100.0
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!
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... !
Connect Four: the object b
This is true for sufficiently broad definitions of “the creators of Python’s library” ...
Boardb
def addMove(self, col, player)
intNROWS
intNCOLS
def allowsMove(self, col)
char char char
char char char
char char char
datalist char
char
char
def winsFor(self, player)
data members
methods
What is player ?
Connect Four: the object b
This is true for sufficiently broad definitions of “the creators of Python’s library” ...
Boardb
def addMove(self, col, player)
intNROWS
intNCOLS
def allowsMove(self, col)
char char char
char char char
char char char
datalist char
char
char
def winsFor(self, player)
data members
methods
Which methods will alter b? Which leave it alone?
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?
Connect Four: Boardclass 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 !
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?
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?
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
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
“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?
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?
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?