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Scholar Sun

Publications and source records attributed to Scholar Sun.

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Powell-Style Model-Based Derivative-Free Optimization with Complexity Guarantees

We propose variants of model-based trust region derivative-free algorithms that are closest to methods initially proposed and implemented by Powell. These methods rely on low degree polynomial interpolation and carefully maintain geometry of the interpolation sets. We are able to derive complexity bounds for these methods that make them theoretically competitive to other derivative-free methods. Applying these methods in randomly generated subspaces recovers what we believe to be nearly tight complexity. This paper builds on recent results where complexity of a much simplified version of Powell's methods was derived. Here, we extend the analysis to fully incorporate Powell's geometry handling approach and conduct an extensive numerical comparison of the model-based trust region methods connecting practical and theoretical performance. We also extend the analysis of subspace model-based trust region methods to the case of noisy function evaluations.

math.OC

On the computation of the cosine measure in high dimensions

In derivative-free optimization, the cosine measure is a value that often arises in the convergence analysis of direct search methods. Given the increasing interest in high-dimensional derivative-free optimization problems, it is valuable to compute the cosine measure in this setting; however, it has recently been shown to be NP-hard. We propose a new formulation of the problem and heuristic to tackle this problem in higher dimensions and compare it with existing algorithms in the literature. In addition, new results are presented to facilitate the construction of sets with specific cosine measures, allowing for the creation of a test-set to benchmark the algorithms with.

math.OC