Harmonic Analysis and Applications

June 4-8, 2018


"Dictionary learning - from local towards global and adaptive"

Schnass, Karin

In this talk we start with a brief introduction to alternating projection algorithms for dictionary learning. We then provide conditions that guarantee one iteration of an alternating dictionary learning scheme to contract an estimate for the desired generating dictionary towards this generating dictionary. Conversely we will provide examples of dictionaries not equal to the generating dictionary that are stable fixed points of the alternating scheme. Based on these characterisations we then propose a (cheap) replacement strategy for alternate dictionary learning to escape local minima (fixed points). Time permitting we will finally discuss how the replacement strategy can be used to automatically determine the dictionary size and sparsity level.

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