Testing different diversity-enhacing migration and replacement policies in dynamic environments (an evolutionary robotics case)

The paper “Testing Diversity-Enhancing Migration Policies for Hybrid On-Line Evolution of Robot Controllers” has been published in Evostar 2012. This work was developed during my foreign stay at the Vrije Universiteit Amsterdam, with Doctor A.E. Eiben. Appart from having a great time of my life in Amsterdam, I did experiments, and science and stuff.

In this work, we present the results obtained from comparing several migration policies that tries to optimize in a noisy fitness environment: the on-line, on-board and hybrid evolutionary robotics problem. Three different migration policies have been studied (the most different migrant, random migrant and best migrant) and two replacement mechanisms: the migrant replaces the worst, or the migrant replaces the worst after being evaluated only if is better. Experiments with 4, 16 and 36 robots were conduced, with two different topologies (ring and panmictic) and also a comparison with other evolutionary robotics algorithms were performed. Results show that the replacement mechanism has more influence than the migration policy or topology, and it also affects the tuning of the algorithm parameters. We asked ourselves the next questions:

  • Using the hybrid approach (island model), which is the best combination of migration policy, admission policy, and island topology?
  • Is this combination better than the encapsulated and distributed alternatives?
  • Does the number of robots affect the result and if so, how?

Conclusions, graphs and stuff and in the paper, but summarizing, multikulti technique (receive the most different individual of my population from other islands) and accept it in my population after its evaluation perform better than other alternatives, even with less migration rate.

You can also check the poster here.

The Springer link to the paper is  Testing Diversity-Enhancing Migration Policies for Hybrid On-Line Evolution of Robot Controllers but you can download the draft.

The abstract:

We investigate on-line on-board evolution of robot controllers based on the so-called hybrid approach (island-based). Inherently to this approach each robot hosts a population (island) of evolving controllers and exchanges controllers with other robots at certain times. We compare different exchange (migration) policies in order to optimize this evolutionary system and compare the best hybrid setup with the encapsulated and distributed alternatives. We conclude that adding a difference-based migrant selection scheme increases the performance.

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