A New Framework for Analysis of Coevolutionary Systems - Directed Graph Representation and Random Walks

Research output: Contribution to journalArticle

Colleges, School and Institutes

External organisations

  • Aberystwyth University

Abstract

Studying coevolutionary systems in the context of simplified models (i.e. games
with pairwise interactions between coevolving solutions modelled as self plays) remains an open challenge since the rich underlying structures associated with pairwise-comparison-based fitness measures are often not taken fully into account. Although cyclic dynamics have been demonstrated in several contexts (such as intransitivity in coevolutionary problems), there is no complete characterization of cycle structures and their effects on coevolutionary search. We develop a new framework to address this issue. At the core of our approach is the directed graph (digraph) representation of coevolutionary problem that fully captures structures in the relations between candidate solutions. Coevolutionary processes are modelled as a specific type of Markov chains - random walks on digraphs. Using this framework, we show that coevolutionary problems admit a qualitative characterization: a coevolutionary problem is
either solvable (there is a subset of solutions that dominates the remaining candidate solutions) or not. This has an implication on coevolutionary search. We further develop our framework that provide the means to construct quantitative tools for analysis of coevolutionary processes and demonstrate their applications through case studies. We show that coevolution of solvable problems corresponds to an absorbing Markov chain for which we can compute the expected hitting time of the absorbing class. Otherwise, coevolution will cycle indefinitely and the quantity of interest will be the limiting invariant distribution of the Markov chain. We also provide an index for characterizing complexity in coevolutionary problems and show how they can be generated in a controlled manner.

Details

Original languageEnglish
Number of pages33
JournalEvolutionary Computation
Early online date20 Nov 2017
Publication statusE-pub ahead of print - 20 Nov 2017

Keywords

  • Coevolution, Directed graphs, Markov chains, Evolutionary Computation, Self play