We present an efficient fixed-parameter algorithm for #SAT parameterized by the incidence treewidth, i.e., the treewidth of the bipartite graph whose vertices are the variables and clauses of the given CNF formula; a variable and a clause are joined by an edge if and only if the variable occurs in the clause. Our algorithm runs in time O(4^k k l N), where k denotes the incidence treewidth, l denotes the size of a largest clause, and N denotes the number of nodes of the tree-decomposition.
We introduce a one-sided incidence tree decomposition of a CNF $φ$. This is a tree decomposition of the incidence graph of $φ$ where the underlying tree is rooted and the set of bags containing each clause induces a directed path in the tree. The one-sided treewidth is the smallest width of a one-sided incidence tree decomposition. We consider a class of unsatisfiable CNF $φ$ that can be turned into one of one sided treewidth at most $k$ by removal of at most $p$ clauses. We show that the size of regular resolution for this class of CNFs is FPT parameterized by $k$ and $p$. The results contrib…
Solving SAT via Treewidth Backdoors in Linear Time: Beyond Sparsity
Hasso Plattner Institute（哈索·普拉特纳研究所）；Algorithms and Complexity Group, TU Wien（维也纳工业大学算法与复杂性组）；Discrete Mathematics Group, Institute for Basic Science (IBS)（基础科学研究所离散数学组）
The recently introduced graph parameter tree-cut width plays a similar role with respect to immersions as the graph parameter treewidth plays with respect to minors. In this paper, we provide the first algorithmic applications of tree-cut width to hard combinatorial problems. Tree-cut width is known to be lower-bounded by a function of treewidth, but it can be much larger and hence has the potential to facilitate the efficient solution of problems that are not known to be fixed-parameter tractable (FPT) when parameterized by treewidth. We introduce the notion of nice tree-cut decompositions an…
Treewidth and hypertree width have proven to be highly successful structural parameters in the context of the Constraint Satisfaction Problem (CSP). When either of these parameters is bounded by a constant, then CSP becomes solvable in polynomial time. However, here the order of the polynomial in the running time depends on the width, and this is known to be unavoidable; therefore, the problem is not fixed-parameter tractable parameterized by either of these width measures. Here we introduce an enhancement of tree and hypertree width through a novel notion of thresholds, allowing the associate…
A strong backdoor in a formula $ϕ$ of propositional logic to a tractable class $\mathcal{C}$ of formulas is a set $B$ of variables of $ϕ$ such that every assignment of the variables in $B$ results in a formula from $\mathcal{C}$. Strong backdoors of small size or with a good structure, e.g. with small backdoor treewidth, lead to efficient solutions for the propositional satisfiability problem SAT. In this paper we propose the new notion of recursive backdoors, which is inspired by the observation that in order to solve SAT we can independently recurse into the components that are created by pa…
Known Algorithms on Graphs of Bounded Treewidth are Probably Optimal
We obtain a number of lower bounds on the running time of algorithms solving problems on graphs of bounded treewidth. We prove the results under the Strong Exponential Time Hypothesis of Impagliazzo and Paturi. In particular, assuming that SAT cannot be solved in (2-ε)^{n}m^{O(1)} time, we show that for any e > 0; { \sc Independent Set } cannot be solved in (2-e)^{tw(G)}|V(G)|^{O(1)} time, { \sc Dominating Set } cannot be solved in (3-e)^{tw(G)}|V(G)|^{O(1)} time, { \sc Max Cut} cannot be solved in (2-e)^{tw(G)}|V(G)|^{O(1)} time, { \sc Odd Cycle Transversal} cannot be solved in (3-e)^{tw(G)}|…
In this paper we propose, implement, and test the first practical decomposition algorithms for the width parameters treecut width and treedepth. These two parameters have recently gained a lot of attention in the theoretical research community as they offer the algorithmic advantage over treewidth by supporting so-called fixed-parameter algorithms for certain problems that are not fixed-parameter tractable with respect to treewidth. However, the existing research has mostly been theoretical. A main obstacle for any practical or experimental use of these two width parameters is the lack of any …
Tree-cut width is a parameter that has been introduced as an attempt to obtain an analogue of treewidth for edge cuts. Unfortunately, in spite of its desirable structural properties, it turned out that tree-cut width falls short as an edge-cut based alternative to treewidth in algorithmic aspects. This has led to the very recent introduction of a simple edge-based parameter called edge-cut width [WG 2022], which has precisely the algorithmic applications one would expect from an analogue of treewidth for edge cuts, but does not have the desired structural properties. In this paper, we study a …
University of Copenhagen（哥本哈根大学）；Department of Computer Science, University of California Santa Barbara（加州大学圣塔芭芭拉分校计算机科学系）；The Institute of Mathematical Sciences, HBNI（HBNI数学科学研究所）
It has long been known that Feedback Vertex Set can be solved in time $2^{\mathcal{O}(w\log w)}n^{\mathcal{O}(1)}$ on $n$-vertex graphs of treewidth $w$, but it was only recently that this running time was improved to $2^{\mathcal{O}(w)}n^{\mathcal{O}(1)}$, that is, to single-exponential parameterized by treewidth. We investigate which generalizations of Feedback Vertex Set can be solved in a similar running time. Formally, for a class $\mathcal{P}$ of graphs, the Bounded $\mathcal{P}$-Block Vertex Deletion problem asks, given a graph~$G$ on $n$ vertices and positive integers~$k$ and~$d$, whet…
The field of knowledge compilation establishes the tractability of many tasks by studying how to compile them to Boolean circuit classes obeying some requirements such as structuredness, decomposability, and determinism. However, in other settings such as intensional query evaluation on databases, we obtain Boolean circuits that satisfy some width bounds, e.g., they have bounded treewidth or pathwidth. In this work, we give a systematic picture of many circuit classes considered in knowledge compilation and show how they can be systematically connected to width measures, through upper and lowe…
Fixed-Parameter Tractability of Private Synthetic Data Generation
Google Deepmind（谷歌DeepMind）；Institute for Mathematical and Computational Engineering, Faculty of Mathematics and School of Engineering, Pontificia Universidad Católica de Chile（数学与计算工程学院、数学系和工程学院、智利天主教大学）
