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G5BAIM Artificial Intelligence Methods

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1 G5BAIM Artificial Intelligence Methods
Graham Kendall History

2 “Within 10 years a computer will be a chess champion”
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 100,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 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
> 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
Microseconds since Big Bang Microseconds in a Day

23 Combinatorial Explosion
Running on a computer capable of 1 million instructions/second 10 20 50 100 200 N2 N5 1/10,000 second 1/2500 second 1/400 second 1/100 second 1/25 second 1/10 second 3.2 seconds 5.2 minutes 2.8 hours 3.7 days 2N NN 1/1000 second 1 second 35.7 years > 400 trillion centuries 45 digit no. of centuries 2.8 hours 3.3 trillion years 70 digit no. of centuries 185 digit no. of centuries 445 digit no. of centuries Ref : Harel, D Computer Ltd. : What they really can’t 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 one’s 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 = Behaviour

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 = Behaviour 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 = Behaviour 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 G5BAIM Artificial Intelligence Methods
Graham Kendall End of History


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