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The Dominance Tournament Method of Monitoring Progress in Coevolution

Speaker: Lin, Wei-Kai (2009/04/30)

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Outline Introduction Experiments and Results Discussion and Future Work Conclusions

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Introduction We want to know if an arms race took place Master Tournament (Cliff and Miller 1995;

Floreano and Nol 1997) is the most common analysis method Every generation champion is compared to every

other generation champion Results show whether wins increase over

generations But does that demonstrate an arms race? Dominance Tournament Test problem: neural network and robot duel

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Master Tournament

The champion of every generation is compared with the champion of all (prior) generations

Count the number of wins

The higher the generation, the more opponents the champion can beat

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Master Tournament - Shortcomings The computational complexty

Tournament between all generations: C(n, 2) Does it really progress?

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Dominance Tournament The first dominant strategy is the champion of

the first generation. A generation champion is a dominant strategy

if it is superior to all previous dominant strategies

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NEAT and Robot Duel The test problem Neuro Evolution of Augmenting Topologies

(NEAT) Adding new structure to existing network, or Evolving only fixed topologies

Robot Duel Eat food to gain energy The robot with higher energy

wins if two robots collide Two food positions is randomly

chosen (from total144 configurations)

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Experiments and Results The two population setup for competitive

coevolution Using master tournament and dominance

tournament Analysis the results in a single run

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Competitive Coevolution Setup Two populations

Host: the population currently being evaluated Parasite: the population from which opponents is

chosen The opponents set consists of

Best strategies in 4 species in the parasite population

8 strategies chosen randomly from a Hall of Fame A single fitness evaluation includes two trials

Starts from the east and the west position.

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Monitoring Progress Champion: the winner of the best strategies in

two populations in a generation in 288 trials Master Tournament

A champion plays all other champions in 2 trial Dominance Tournament

144 x 2 = 288 trials between a dominant strategy and a champion

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Results

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Dominance Tournament Results

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Observations from Dominance Tournament The progress after 200 generations Higher level of dominance takes more time to

reach The 17th dominant strategy won 221/288 trials

(compared with the 14th level in the fixed topology)

Circularities discovered A champion is able to defeat some but not all of

dominant strategies Complexifying and fixed topology occurs 48 and

93 times Dominance tournament takes 738

comparisons, but master tournament takes 124,750

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Discussion and Future Work For multiple runs, such analysis can also be

applied The highest level of dominance Equivalent dominance level Equivalent generation Other population statistic: the network complexity

The initialization of the first dominant strategy The first champion: natural and poor enough The first champion that defeats serveral

champions from the first few generations

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Dominance Tournament withDifferent Roles New dominant strategy must defeat all

previous dominant strategies from opposing population

Ranking alternates

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Conclusion The tournament dominance provides specific

details necessary for drawing strong conclusions

The best individual is well defined We are able to conclude that the arms race

continued Lower computational complexity Test specific claims by making comparisons

between different runs