论文标题
关于分支证明的复杂性
On the Complexity of Branching Proofs
论文作者
论文摘要
我们考虑使用一般的分支证明系统来证明有界凸$ k $ in $ \ mathbb {r}^n $的整数不可行的任务。在一般的分支证明中,一个人通过添加整数分离$ \ mathbf {a} \ Mathbf {x} \ leq b $或$ \ Mathbf {a} \ MathBf {x} \ geq b+1 $,$ \ m i; \ Mathbb {z} $,在每个节点上,使树的叶子对应于空集(即$ k $,以及从根到叶的不等式的不等式,是空的)。最近,Beame等人(ITCS 2018)询问分支证明中的系数的位大小(他们将其命名为刺刺平面(SP)反驳)是否可以假定为来自SAT公式的多面体,可以假定在$ n $中是多项式的。 We resolve this question by showing that any branching proof can be recompiled so that the integer disjunctions have coefficients of size at most $(n R)^{O(n^2)}$, where $R \in \mathbb{N}$ such that $K \in R \mathbb{B}_1^n$, while increasing the number of nodes in the branching tree by at most a factor $ O(n)$。作为我们的第二个贡献,我们表明三素公式是一类重要的不可行的SAT实例,具有准多项式切割平面(CP)的反应,表明了TSEITIN蛋白配方(指数为正值)CP的猜想。作为我们的最终贡献,我们为$ [0,1]^n $提供了一个简单的多型家族,需要长度为$ 2^n/n $的分支证明。
We consider the task of proving integer infeasibility of a bounded convex $K$ in $\mathbb{R}^n$ using a general branching proof system. In a general branching proof, one constructs a branching tree by adding an integer disjunction $\mathbf{a} \mathbf{x} \leq b$ or $\mathbf{a} \mathbf{x} \geq b+1$, $\mathbf{a} \in \mathbb{Z}^n$, $b \in \mathbb{Z}$, at each node, such that the leaves of the tree correspond to empty sets (i.e., $K$ together with the inequalities picked up from the root to leaf is empty). Recently, Beame et al (ITCS 2018), asked whether the bit size of the coefficients in a branching proof, which they named stabbing planes (SP) refutations, for the case of polytopes derived from SAT formulas, can be assumed to be polynomial in $n$. We resolve this question by showing that any branching proof can be recompiled so that the integer disjunctions have coefficients of size at most $(n R)^{O(n^2)}$, where $R \in \mathbb{N}$ such that $K \in R \mathbb{B}_1^n$, while increasing the number of nodes in the branching tree by at most a factor $O(n)$. As our second contribution, we show that Tseitin formulas, an important class of infeasible SAT instances, have quasi-polynomial sized cutting plane (CP) refutations, disproving the conjecture that Tseitin formulas are (exponentially) hard for CP. As our final contribution, we give a simple family of polytopes in $[0,1]^n$ requiring branching proofs of length $2^n/n$.