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CS440 Computer Science Seminar. Introduction to Evolutionary Computing. Adaptation to environment. Traveling salesman problem. A salesperson must visit clients in different cities, and then return home. What is the shortest tour through those cities, visiting each one once and only once?
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CS440 Computer Science Seminar Introduction to Evolutionary Computing
Traveling salesman problem • A salesperson must visit clients in different cities, and then return home. What is the shortest tour through those cities, visiting each one once and only once? • No known algorithms are able to generate the best answer in an amount time that grow only as a polynomial function of the number of elements (cities) in the problem. • Belongs in the NP-hard class of problems, where NP stands for non-deterministic polynomial. For 100 cities, there are over 10155 different possible paths through all cities. The Universe is only 1018 seconds old!
Steps of evolutionary approach to discovering solutions • Choosing the solution representation • Devising a random variation operator • Determining a rule for solution survival • Initialization the population
Solving the traveling salesman problem: 1. Solution representation, 2. Devising random variation operator
Solving the traveling salesman problem: 3. Determining the rule for solution survival, 4. Initialize the population • Rule for survival: survival of the fittest—the least total distance traveled. • Initial population: in this case, chosen completely at random from the space of possible solutions.
The best result of the 1st generation for the 100-city traveling salesman problem
The best result of the 500th generation for the 100-city traveling salesman problem
The best result of the 1000th generation for the 100-city traveling salesman problem
The best result of the 4000th generation for the 100-city traveling salesman problem
To probe further • What is revolutionary computation, IEEE Spectrum, Feb. 2000 • How to solve It: Modern Heuristics, Zbigniew Michalewicz, Springer, 2000 • Evolution, Neural Networks, Games, and Intelligence, Kumar and Fogel, Proceedings of IEEE Vol. 87, no 9, pp. 1471-96, Sept. 1999