论文标题

重新访问Tardos的线性编程框架:使用近似求解器更快的精确解决方案

Revisiting Tardos's Framework for Linear Programming: Faster Exact Solutions using Approximate Solvers

论文作者

Dadush, Daniel, Natura, Bento, Végh, László A.

论文摘要

在突破性工作中,Tardos(操作。'86)给出了一个基于近距离的框架,用于及时求解线性编程(LP),仅取决于位复杂性模型中的约束矩阵。在Tar​​dos的框架中,一个人可以减少解决Lp $ \ min \ langle c,{x} \ rangle $,$ ax = b $,$ x \ geq 0 $,$ a \ in \ in \ mathbb {z}^{z}^{m \ times n} n} $ coggeft in $(nm) 算法。这引起了时间poly $(n,m \logΔ_a)$的LP算法,其中$Δ_A$是$ a $的最大次级次数。 Vavasis和Ye(Math。Prog。'96)给出了对实际计算模型的显着扩展,给出了一种专门的内部方法,该方法在时间poly $(n,m,m,\ log \barχ_a)$中运行,这取决于Stewart的$ \\\barχ_a$,一个良好的条件编号。 在这项工作中,我们扩展了Tardos的原始框架,以获得这样的运行时间依赖性。特别是,我们用近似LP替换了确切的LP求解,使我们能够直接利用最近的算法进度来实现近似线性编程。更确切地说,我们表明,精确解决$ a $中的任何LP所需的基本“准确性”是$ n $和$ \ log \barχ_a$的逆多项式。我们的方法插入了Van Den Brand(Soda '20)的最新算法,使用$ {O}(M n^{ω+1} \ log(n)\ log(\ barχ_a+n))计算最佳原始和双重解决方案。 在技​​术层面上,我们的框架将近似LP解决方案结合在一起,以计算确切的解决方案,利用建设性接近定理(绑定了“附近” LPS的解决方案之间的距离),以保持所需的准确性较低。

In breakthrough work, Tardos (Oper. Res. '86) gave a proximity based framework for solving linear programming (LP) in time depending only on the constraint matrix in the bit complexity model. In Tardos's framework, one reduces solving the LP $\min \langle c,{x}\rangle$, $Ax=b$, $x \geq 0$, $A \in \mathbb{Z}^{m \times n}$, to solving $O(nm)$ LPs in $A$ having small integer coefficient objectives and right-hand sides using any exact LP algorithm. This gives rise to an LP algorithm in time poly$(n,m\logΔ_A)$, where $Δ_A$ is the largest subdeterminant of $A$. A significant extension to the real model of computation was given by Vavasis and Ye (Math. Prog. '96), giving a specialized interior point method that runs in time poly$(n,m,\log\barχ_A)$, depending on Stewart's $\barχ_A$, a well-studied condition number. In this work, we extend Tardos's original framework to obtain such a running time dependence. In particular, we replace the exact LP solves with approximate ones, enabling us to directly leverage the tremendous recent algorithmic progress for approximate linear programming. More precisely, we show that the fundamental "accuracy" needed to exactly solve any LP in $A$ is inverse polynomial in $n$ and $\log\barχ_A$. Plugging in the recent algorithm of van den Brand (SODA '20), our method computes an optimal primal and dual solution using ${O}(m n^{ω+1} \log (n)\log(\barχ_A+n))$ arithmetic operations, outperforming the specialized interior point method of Vavasis and Ye and its recent improvement by Dadush et al (STOC '20). At a technical level, our framework combines together approximate LP solutions to compute exact ones, making use of constructive proximity theorems -- which bound the distance between solutions of "nearby" LPs -- to keep the required accuracy low.

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