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arXiv · 2101.01631

On the Approximation Relationship between Optimizing Ratio of Submodular (RS) and Difference of Submodular (DS) Functions

Pierre Perrault·Jennifer Healey·Zheng Wen·Michal Valko
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Abstract

We demonstrate that from an algorithm guaranteeing an approximation factor for the ratio of submodular (RS) optimization problem, we can build another algorithm having a different kind of approximation guarantee -- weaker than the classical one -- for the difference of submodular (DS) optimization problem, and vice versa. We also illustrate the link between these two problems by analyzing a \textsc{Greedy} algorithm which approximately maximizes objective functions of the form $\Psi(f,g)$, where $f,g$ are two non-negative, monotone, submodular functions and $\Psi$ is a {quasiconvex} 2-variables function, which is non decreasing with respect to the first variable. For the choice $\Psi(f,g)\triangleq f/g$, we recover RS, and for the choice $\Psi(f,g)\triangleq f-g$, we recover DS. To the best of our knowledge, this greedy approach is new for DS optimization. For RS optimization, it reduces to the standard \textsc{GreedRatio} algorithm that has already been analyzed previously. However, our analysis is novel for this case.

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Pierre Perrault, Jennifer Healey, Zheng Wen, Michal Valko. 2021-01-05. On the Approximation Relationship between Optimizing Ratio of Submodular (RS) and Difference of Submodular (DS) Functions. https://arxiv.org/abs/2101.01631

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