G5BAIM Artificial Intelligence Methods

1
G5BAIMArtificial Intelligence Methods

• Graham Kendall

History
2
Predictions

• Within 10 years a computer will be a chess
  champion
• Herbert Simon, 1958
• Conversion from Russian to English, when
  presented with
• The spirit is willing but the flesh is weak
  produced
• The vodka is good but the meat is rotten
• National Research Council, 1957

3
The Travelling Salesman Problem

• A salesperson has to visit a number of cities
• (S)He can start at any city and must finish at
  that same city
• The salesperson must visit each city only once
• The number of possible routes is (n!)/2

4
Combinatorial Explosion
5
Combinatorial Explosion
6
Combinatorial Explosion
A 10 city TSP has 181,000 possible solutions A 20
city TSP has 10,000,000,000,000,000 possible
solutions A 50 City TSP has 100,000,000,000,000,00
0,000,000,000,000,000,000,000,000,000,000,000,000,
000,000,000 possible solutions
There are 1,000,000,000,000,000,000,000 litres of
water on the planet
Mchalewicz, Z, Evolutionary Algorithms for
Constrained Optimization Problems, CEC 2000
(Tutorial)
7
Combinatorial Explosion - Towers of Hanoi
8
Combinatorial Explosion - Towers of Hanoi
9
Combinatorial Explosion - Towers of Hanoi
10
Combinatorial Explosion - Towers of Hanoi
11
Combinatorial Explosion - Towers of Hanoi
12
Combinatorial Explosion - Towers of Hanoi
13
Combinatorial Explosion - Towers of Hanoi
14
Combinatorial Explosion - Towers of Hanoi
15
Combinatorial Explosion - Towers of Hanoi

• How many moves does it take to move four rings?
• You might like to try writing a towers of hanoi
  program (and you may well have to in one of your
  courses!)

16
Combinatorial Explosion - Towers of Hanoi

• If you are interested in an algorithm here is a
  very simple one
• Assume the pegs are arranged in a circle
• 1. Do the following until 1.2 cannot be done
• 1.1 Move the smallest ring to the peg residing
  next to it, in clockwise order
• 1.2 Make the only legal move that does not
  involve the smallest ring
• 2. Stop
• P. Buneman and L.Levy (1980). The Towers of Hanoi
  Problem, Information Processing Letters, 10, 243-4

17
Combinatorial Explosion - Towers of Hanoi

• A time analysis of the problem shows that the
  lower bound for the number of moves is
• 2N-1
• Since N appears as the exponent we have an
  exponential function

18
Combinatorial Explosion - Towers of Hanoi
19
Combinatorial Explosion - Towers of Hanoi

• The original problem was stated that a group of
  tibetan monks had to move 64 gold rings which
  were placed on diamond pegs.
• When they finished this task the world would end.
• Assume they could move one ring every second (or
  more realistically every five seconds).
• How long till the end of the world?

20
Combinatorial Explosion - Towers of Hanoi

• gt 500,000 years!!!!! Or 3 Trillion years
• Using a computer we could do many more moves than
  one second so go and try implementing the 64
  rings towers of hanoi problem.
• If you are still alive at the end, try 1,000
  rings!!!!

21
Combinatorial Explosion - Optimization

• Optimize f(x1, x2,, x100)
• where f is complex and xi is 0 or 1
• The size of the search space is 2100 ? 1030
• An exhaustive search is not an option
• At 1000 evaluations per second
• Start the algorithm at the time the universe was
  created
• As of now we would have considered 1 of all
  possible solutions

22
Combinatorial Explosion
23
Combinatorial Explosion
Running on a computer capable of 1 million
instructions/second
Ref Harel, D. 2000. Computer Ltd. What they
really cant do, Oxford University Press
24
Definition of AI
Systems that think like humans
Systems that think rationally
Systems that act like humans
Systems that act rationally
25
Definition of AI
Systems that think like humans
Systems that think rationally
Systems that act like humans
Systems that act rationally
Top Left Cognitive Science
26
Definition of AI
Systems that think like humans
Systems that think rationally
Systems that act like humans
Systems that act rationally
Top Left Cognitive Science Bottom Left The
Turing Test
27
Definition of AI
Systems that think like humans
Systems that think rationally
Systems that act like humans
Systems that act rationally
Top Left Cognitive Science Bottom Left The
Turing Test Top Right Logical Approach
28
Definition of AI
Systems that think like humans
Systems that think rationally
Systems that act like humans
Systems that act rationally
Top Left Cognitive Science Bottom Left The
Turing Test Top Right Logical Approach Bottom
Right Acting to achieve ones goals
29
Definition of AI
Systems that think like humans
Systems that think rationally
Systems that act like humans
Systems that act rationally
Top Thought Processes and Reasoning
30
Definition of AI
Systems that think like humans
Systems that think rationally
Systems that act like humans
Systems that act rationally
Top Thought Processes and Reasoning Bottom Beh
aviour
31
Definition of AI
Systems that think like humans
Systems that think rationally
Systems that act like humans
Systems that act rationally
Top Thought Processes and Reasoning Bottom Beh
aviour Left Measure success against ourselves
32
Definition of AI
Systems that think like humans
Systems that think rationally
Systems that act like humans
Systems that act rationally
Top Thought Processes and Reasoning Bottom Beh
aviour Left Measure success against
ourselves Right Measure against rationality
33
Definition of AI
Systems that think like humans
Systems that think rationally
Systems that act like humans
Systems that act rationally
34
Not Examinable - but in notes

• Turing Test
• Chinese Room
• Physical Symbol System Hypothesis
• ELIZA
• MYCIN
• Forward/Backward Chaining
• Means End Analysis

35
G5BAIMArtificial Intelligence Methods

• Graham Kendall

End of History