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arXiv · 2305.16933

Representing Piecewise Linear Functions by Functions with Small Arity

Christoph Koutschan·Bernhard Moser·Anton Ponomarchuk·Josef Schicho
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Abstract

A piecewise linear function can be described in different forms: as an arbitrarily nested expression of $\min$- and $\max$-functions, as a difference of two convex piecewise linear functions, or as a linear combination of maxima of affine-linear functions. In this paper, we provide two main results: first, we show that for every piecewise linear function there exists a linear combination of $\max$-functions with at most $n+1$ arguments, and give an algorithm for its computation. Moreover, these arguments are contained in the finite set of affine-linear functions that coincide with the given function in some open set. Second, we prove that the piecewise linear function $\max(0, x_{1}, \ldots, x_{n})$ cannot be represented as a linear combination of maxima of less than $n+1$ affine-linear arguments. This was conjectured by Wang and Sun in 2005 in a paper on representations of piecewise linear functions as linear combination of maxima.

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Christoph Koutschan, Bernhard Moser, Anton Ponomarchuk, Josef Schicho. 2023-05-26. Representing Piecewise Linear Functions by Functions with Small Arity. https://arxiv.org/abs/2305.16933

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