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arXiv 2003.07817math.COmath.OC
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整数规划中线性松弛的复杂性

Complexity of linear relaxations in integer programming

Gennadiy Averkov, Matthias Schymura

摘要:

对于多面体中的整数点集$X$,其整数点集与$X$重合的任何多面体的最小面数称为松弛复杂度$\mathrm{rc}(X)$。该参数由Kaibel & Weltge(2015)引入,并在不使用辅助变量的情况下捕获$X$的线性描述的复杂性。使用组合数学,数的几何数字,量词消除的工具,我们取得了进展的几个悬而未决的问题,$\mathrm{rc}(X)$及其变体$\mathrm{rc}_{\mathbb{Q}}(X)$,限制$X$的描述有理多面体。作为我们的主要结果,我们证明了当(a)$X$至多为4维,(b)$X$表示$(\mathbb{Z}/2\mathbb{Z})^d$中的每一个剩余类,(c)$X$的凸包包含一个内部整数点,或(d)$X$的格宽大于某个阈值时,$\mathrm{rc}(X) = \mathrm{rc}_{\mathbb{Q}}(X)$是可解的.另外,当$X$至多是三维的或者$X$满足上述条件(b)、(c)或(d)之一时,可以通过算法计算$\mathrm{rc}(X)$。此外,我们还根据$X$的维数得到了一个改进的$\mathrm{rc}(X)$的下界.

英文摘要:

For a set $X$ of integer points in a polyhedron, the smallest number of facets of any polyhedron whose set of integer points coincides with $X$ is called the relaxation complexity $\mathrm{rc}(X)$. This parameter was introduced by Kaibel & Weltge (2015) and captures the complexity of linear descriptions of $X$ without using auxiliary variables. Using tools from combinatorics, geometry of numbers, and quantifier elimination, we make progress on several open questions regarding $\mathrm{rc}(X)$ and its variant $\mathrm{rc}_{\mathbb{Q}}(X)$, restricting the descriptions of $X$ to rational polyhedra. As our main results we show that $\mathrm{rc}(X) = \mathrm{rc}_{\mathbb{Q}}(X)$ when: (a) $X$ is at most four-dimensional, (b) $X$ represents every residue class in $(\mathbb{Z}/2\mathbb{Z})^d$, (c) the convex hull of $X$ contains an interior integer point, or (d) the lattice-width of $X$ is above a certain threshold. Additionally, $\mathrm{rc}(X)$ can be algorithmically computed when $X$ is at most three-dimensional, or $X$ satisfies one of the conditions (b), (c), or (d) above. Moreover, we obtain an improved lower bound on $\mathrm{rc}(X)$ in terms of the dimension of $X$.

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