Abstract

Estimations of distribution algorithms (EDAs) are a major branch of evolutionary algorithms (EA) with some unique advantages in principle. They are able to take advantage of correlation structure to drive the search more efficiently, and they are able to provide insights about the structure of the search space. However, model building in high dimensions is extremely challenging, and as a result existing EDAs may become less attractive in large-scale problems because of the associated large computational requirements. Large-scale continuous global optimisation is key to many modern-day real-world problems. Scaling up EAs to large-scale problems has become one of the biggest challenges of the field. This paper pins down some fundamental roots of the problem and makes a start at developing a new and generic framework to yield effective and efficient EDA-type algorithms for large-scale continuous global optimisation problems. Our concept is to introduce an ensemble of random projections to low dimensions of the set of fittest search points as a basis for developing a new and generic divide-and-conquer methodology. Our ideas are rooted in the theory of random projections developed in theoretical computer science, and in developing and analysing our framework we exploit some recent results in nonasymptotic random matrix theory.

Highlights

  • Estimation of distribution algorithms (EDAs) are population-based stochastic blackbox optimisation methods that have been recognised as a major paradigm of Evolutionary Computation (EC) (Larranaga and Lozano, 2002)

  • The EDA-type approach we develop in this paper keeps with the general idea of reducing the degrees of freedom of the covariance, but without making such binary decisions on any of the individual dependencies

  • Of the d/m-group nonseparable functions the algorithm we proposed is the overall winner on T9, it is outperformed by EDA-MCC and partly by DECC-CG on F10, and outperformed by four competitors on T11

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Summary

Introduction

Estimation of distribution algorithms (EDAs) are population-based stochastic blackbox optimisation methods that have been recognised as a major paradigm of Evolutionary Computation (EC) (Larranaga and Lozano, 2002). More refined univariate methods are sep-CMA-ES (Ros and Hansen, 2008) and the univariate version of AMaLGaM (Bosman, 2009); these only estimate the diagonal entries of the sample covariance matrix to reduce the search cost of model building, in a different way than UMDAc does. By construction, these methods are aimed at dealing with dimension-wise separable problems, and this serves as an approximation of nonseparable problems with few dependencies. A preliminary version of this work appeared in (Kaban et al, 2013)

On the challenges of model estimation in high dimensions
Approach
New search operators for EDA
Inputs
Output
Analysis of the algorithm that creates new generations
Infinitely many random projections
Finitely many random projections
Computational complexity per generation
Alternative random projections matrices
Experiments
A fully nonseparable function: T12
Fitness trajectories through the generations
Impact of the parameters and generic guidelines for setting the parameters
Scalability experiments
Outlook and future work
Full Text
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