当前期刊: Journal of the ACM Go to current issue    加入关注    本刊投稿指南
显示样式:        排序: IF: - GO 导出
  • The Marriage of Univalence and Parametricity
    J. ACM (IF 1.686) Pub Date : 2021-01-15
    Nicolas Tabareau; Éric Tanter; Matthieu Sozeau

    Reasoning modulo equivalences is natural for everyone, including mathematicians. Unfortunately, in proof assistants based on type theory, which are frequently used to mechanize mathematical results and carry out program verification efforts, equality is appallingly syntactic, and as a result, exploiting equivalences is cumbersome at best. Parametricity and univalence are two major concepts that have

  • Invited Article Foreword
    J. ACM (IF 1.686) Pub Date : 2021-01-15
    Eva Tardos

    No abstract available.

  • Uniform, Integral, and Feasible Proofs for the Determinant Identities
    J. ACM (IF 1.686) Pub Date : 2021-01-13
    Iddo Tzameret; Stephen A. Cook

    Aiming to provide weak as possible axiomatic assumptions in which one can develop basic linear algebra, we give a uniform and integral version of the short propositional proofs for the determinant identities demonstrated over GF(2) in Hrubeš-Tzameret [15]. Specifically, we show that the multiplicativity of the determinant function and the Cayley-Hamilton theorem over the integers are provable in the

  • Mildly Short Vectors in Cyclotomic Ideal Lattices in Quantum Polynomial Time
    J. ACM (IF 1.686) Pub Date : 2021-01-06
    Ronald Cramer; Léo Ducas; Benjamin Wesolowski

    In this article, we study the geometry of units and ideals of cyclotomic rings and derive an algorithm to find a mildly short vector in any given cyclotomic ideal lattice in quantum polynomial time, under some plausible number-theoretic assumptions. More precisely, given an ideal lattice of the cyclotomic ring of conductor m, the algorithm finds an approximation of the shortest vector by a factor exp

  • EPTAS and Subexponential Algorithm for Maximum Clique on Disk and Unit Ball Graphs
    J. ACM (IF 1.686) Pub Date : 2021-01-06
    Marthe Bonamy; Édouard Bonnet; Nicolas Bousquet; Pierre Charbit; Panos Giannopoulos; Eun Jung Kim; Paweł Rzążewski; Florian Sikora; Stéphan Thomassé

    A (unit) disk graph is the intersection graph of closed (unit) disks in the plane. Almost three decades ago, an elegant polynomial-time algorithm was found for MAXIMUM CLIQUE on unit disk graphs [Clark, Colbourn, Johnson; Discrete Mathematics ’90]. Since then, it has been an intriguing open question whether or not tractability can be extended to general disk graphs. We show that the disjoint union

  • Bernoulli Factories and Black-box Reductions in Mechanism Design
    J. ACM (IF 1.686) Pub Date : 2021-01-06
    Shaddin Dughmi; Jason Hartline; Robert D. Kleinberg; Rad Niazadeh

    We provide a polynomial time reduction from Bayesian incentive compatible mechanism design to Bayesian algorithm design for welfare maximization problems. Unlike prior results, our reduction achieves exact incentive compatibility for problems with multi-dimensional and continuous type spaces. The key technical barrier preventing exact incentive compatibility in prior black-box reductions is that repairing

  • Solving Linear Programs in the Current Matrix Multiplication Time
    J. ACM (IF 1.686) Pub Date : 2021-01-05
    Michael B. Cohen; Yin Tat Lee; Zhao Song

    This article shows how to solve linear programs of the form minAx=b,x≥ 0 c⊤ x with n variables in time O*((nω+n2.5−α/2+n2+1/6) log (n/δ)), where ω is the exponent of matrix multiplication, α is the dual exponent of matrix multiplication, and δ is the relative accuracy. For the current value of ω δ 2.37 and α δ 0.31, our algorithm takes O*(nω log (n/δ)) time. When ω = 2, our algorithm takes O*(n2+1/6

  • The Reachability Problem for Petri Nets Is Not Elementary
    J. ACM (IF 1.686) Pub Date : 2020-12-20
    Wojciech Czerwiński; Sławomir Lasota; Ranko Lazić; JÉrôme Leroux; Filip Mazowiecki

    Petri nets, also known as vector addition systems, are a long established model of concurrency with extensive applications in modeling and analysis of hardware, software, and database systems, as well as chemical, biological, and business processes. The central algorithmic problem for Petri nets is reachability: whether from the given initial configuration there exists a sequence of valid execution

  • Game Semantics for Interface Middleweight Java
    J. ACM (IF 1.686) Pub Date : 2020-12-10
    Andrzej S. Murawski; Nikos Tzevelekos

    We consider an object calculus in which open terms interact with the environment through interfaces. The calculus is intended to capture the essence of contextual interactions of Middleweight Java code. Using game semantics, we provide fully abstract models for the induced notions of contextual approximation and equivalence. These are the first denotational models of this kind.

  • On Small-depth Frege Proofs for Tseitin for Grids
    J. ACM (IF 1.686) Pub Date : 2020-11-17
    Johan Håstad

    We prove that a small-depth Frege refutation of the Tseitin contradiction on the grid requires subexponential size. We conclude that polynomial size Frege refutations of the Tseitin contradiction must use formulas of almost logarithmic depth.

  • Enhanced Phase Clocks, Population Protocols, and Fast Space Optimal Leader Election
    J. ACM (IF 1.686) Pub Date : 2020-11-17
    Leszek Gąsieniec; Grzegorz Stachowiak

    The model of population protocols refers to the growing in popularity theoretical framework suitable for studying pairwise interactions within a large collection of simple indistinguishable entities, frequently called agents. In this article, the emphasis is on the space complexity of fast leader election in population protocols governed by the random scheduler, which uniformly at random selects pairwise

  • Polynomiality for Bin Packing with a Constant Number of Item Types
    J. ACM (IF 1.686) Pub Date : 2020-11-07
    Michel X. Goemans; Thomas Rothvoss

    We consider the bin packing problem with d different item sizes si and item multiplicities ai, where all numbers are given in binary encoding. This problem formulation is also known as the one-dimensional cutting stock problem. In this work, we provide an algorithm that, for constant d, solves bin packing in polynomial time. This was an open problem for all d\ge 3. In fact, for constant d our algorithm

  • Invited Articles Foreword
    J. ACM (IF 1.686) Pub Date : 2020-11-03
    Eva Tardos

    No abstract available.

  • A Constant-factor Approximation Algorithm for the Asymmetric Traveling Salesman Problem
    J. ACM (IF 1.686) Pub Date : 2020-11-03
    Ola Svensson; Jakub Tarnawski; László A. Végh

    We give a constant-factor approximation algorithm for the asymmetric traveling salesman problem (ATSP). Our approximation guarantee is analyzed with respect to the standard LP relaxation, and thus our result confirms the conjectured constant integrality gap of that relaxation. The main idea of our approach is a reduction to Subtour Partition Cover, an easier problem obtained by significantly relaxing

  • Semantic Optimization of Conjunctive Queries
    J. ACM (IF 1.686) Pub Date : 2020-10-28
    Pablo Barceló; Diego Figueira; Georg Gottlob; Andreas Pieris

    This work deals with the problem of semantic optimization of the central class of conjunctive queries (CQs). Since CQ evaluation is NP-complete, a long line of research has focussed on identifying fragments of CQs that can be efficiently evaluated. One of the most general restrictions corresponds to generalized hypetreewidth bounded by a fixed constant k ≥ 1; the associated fragment is denoted GHWk

  • Approximating Edit Distance Within Constant Factor in Truly Sub-quadratic Time
    J. ACM (IF 1.686) Pub Date : 2020-10-28
    Diptarka Chakraborty; Debarati Das; Elazar Goldenberg; Michal Koucký; Michael Saks

    Edit distance is a measure of similarity of two strings based on the minimum number of character insertions, deletions, and substitutions required to transform one string into the other. The edit distance can be computed exactly using a dynamic programming algorithm that runs in quadratic time. Andoni, Krauthgamer, and Onak (2010) gave a nearly linear time algorithm that approximates edit distance

  • A Unified Translation of Linear Temporal Logic to ω-Automata
    J. ACM (IF 1.686) Pub Date : 2020-10-17
    Javier Esparza; Jan Křetínský; Salomon Sickert

    We present a unified translation of linear temporal logic (LTL) formulas into deterministic Rabin automata (DRA), limit-deterministic Büchi automata (LDBA), and nondeterministic Büchi automata (NBA). The translations yield automata of asymptotically optimal size (double or single exponential, respectively). All three translations are derived from one single Master Theorem of purely logical nature.

  • Near-optimal Sample Complexity Bounds for Robust Learning of Gaussian Mixtures via Compression Schemes
    J. ACM (IF 1.686) Pub Date : 2020-10-06
    Hassan Ashtiani; Shai Ben-David; Nicholas J. A. Harvey; Christopher Liaw; Abbas Mehrabian; Yaniv Plan

    We introduce a novel technique for distribution learning based on a notion of sample compression. Any class of distributions that allows such a compression scheme can be learned with few samples. Moreover, if a class of distributions has such a compression scheme, then so do the classes of products and mixtures of those distributions. As an application of this technique, we prove that ˜Θ(kd2/ε2) samples

  • Oracle-efficient Online Learning and Auction Design
    J. ACM (IF 1.686) Pub Date : 2020-09-29
    Miroslav Dudíte;k; Nika Haghtalab; Haipeng Luo; Robert E. Schapire; Vasilis Syrgkanis; Jennifer Wortman Vaughan

    We consider the design of computationally efficient online learning algorithms in an adversarial setting in which the learner has access to an offline optimization oracle. We present an algorithm called Generalized Follow-the-Perturbed-Leader and provide conditions under which it is oracle-efficient while achieving vanishing regret. Our results make significant progress on an open problem raised by

  • Parallelism in Randomized Incremental Algorithms
    J. ACM (IF 1.686) Pub Date : 2020-09-19
    Guy E. Blelloch; Yan Gu; Julian Shun; Yihan Sun

    In this article, we show that many sequential randomized incremental algorithms are in fact parallel. We consider algorithms for several problems, including Delaunay triangulation, linear programming, closest pair, smallest enclosing disk, least-element lists, and strongly connected components. We analyze the dependencies between iterations in an algorithm and show that the dependence structure is

  • Invited Articles Foreword
    J. ACM (IF 1.686) Pub Date : 2020-09-19
    Eva Tardos

    No abstract available.

  • Universally Composable Security
    J. ACM (IF 1.686) Pub Date : 2020-09-16
    Ran Canetti

    This work presents a general framework for describing cryptographic protocols and analyzing their security. The framework allows specifying the security requirements of practically any cryptographic task in a unified and systematic way. Furthermore, in this framework the security of protocols is preserved under a general composition operation, called universal composition. The proposed framework with

  • Automating Resolution is NP-Hard
    J. ACM (IF 1.686) Pub Date : 2020-09-01
    Albert Atserias; Moritz Müller

    We show that the problem of finding a Resolution refutation that is at most polynomially longer than a shortest one is NP-hard. In the parlance of proof complexity, Resolution is not automatable unless P = NP. Indeed, we show that it is NP-hard to distinguish between formulas that have Resolution refutations of polynomial length and those that do not have subexponential length refutations. This also

  • A Proof of the CSP Dichotomy Conjecture
    J. ACM (IF 1.686) Pub Date : 2020-08-26
    Dmitriy Zhuk

    Many natural combinatorial problems can be expressed as constraint satisfaction problems. This class of problems is known to be NP-complete in general, but certain restrictions on the form of the constraints can ensure tractability. The standard way to parameterize interesting subclasses of the constraint satisfaction problem is via finite constraint languages. The main problem is to classify those

  • Planar Graphs Have Bounded Queue-Number
    J. ACM (IF 1.686) Pub Date : 2020-08-06
    Vida Dujmović; Gwenaël Joret; Piotr Micek; Pat Morin; Torsten Ueckerdt; David R. Wood

    We show that planar graphs have bounded queue-number, thus proving a conjecture of Heath et al. [66] from 1992. The key to the proof is a new structural tool called layered partitions, and the result that every planar graph has a vertex-partition and a layering, such that each part has a bounded number of vertices in each layer, and the quotient graph has bounded treewidth. This result generalises

  • The Log-Approximate-Rank Conjecture Is False
    J. ACM (IF 1.686) Pub Date : 2020-06-21
    Arkadev Chattopadhyay; Nikhil S. Mande; Suhail Sherif

    We construct a simple and total Boolean function F = f ○ XOR on 2n variables that has only O(√n) spectral norm, O(n2) approximate rank, and O(n2.5) approximate nonnegative rank. We show it has polynomially large randomized bounded-error communication complexity of Ω(√n). This yields the first exponential gap between the logarithm of the approximate rank and randomized communication complexity for total

  • A Simple and Approximately Optimal Mechanism for an Additive Buyer
    J. ACM (IF 1.686) Pub Date : 2020-06-16
    Moshe Babaioff; Nicole Immorlica; Brendan Lucier; S. Matthew Weinberg

    We consider a monopolist seller with n heterogeneous items, facing a single buyer. The buyer has a value for each item drawn independently according to (non-identical) distributions, and her value for a set of items is additive. The seller aims to maximize his revenue. We suggest using the a priori better of two simple pricing methods: selling the items separately, each at its optimal price, and bundling

  • Forcing and Calculi for Hybrid Logics
    J. ACM (IF 1.686) Pub Date : 2020-08-06
    Daniel Găină

    The definition of institution formalizes the intuitive notion of logic in a category-based setting. Similarly, the concept of stratified institution provides an abstract approach to Kripke semantics. This includes hybrid logics, a type of modal logics expressive enough to allow references to the nodes/states/worlds of the models regarded as relational structures, or multi-graphs. Applications of hybrid

  • The Power of Shunning: Efficient Asynchronous Byzantine Agreement Revisited*
    J. ACM (IF 1.686) Pub Date : 2020-05-13
    Laasya Bangalore; Ashish Choudhury; Arpita Patra

    The problem of Byzantine Agreement (BA) is of interest to both the distributed computing and cryptography communities. Following well-known results from distributed computing literature, the BA problem in the asynchronous network setting encounters inevitable non-termination issues. The impasse is overcome via randomization that allows construction of BA protocols in two flavors of termination guarantee—with

  • Distributed Exact Shortest Paths in Sublinear Time
    J. ACM (IF 1.686) Pub Date : 2020-05-13
    Michael Elkin

    The distributed single-source shortest paths problem is one of the most fundamental and central problems in the message-passing distributed computing. Classical Bellman-Ford algorithm solves it in O(n) time, where n is the number of vertices in the input graph G. Peleg and Rubinovich [49] showed a lower bound of ˜Ω(D + √ n) for this problem, where D is the hop-diameter of G. Whether or not this problem

  • Representative Sets and Irrelevant Vertices: New Tools for Kernelization
    J. ACM (IF 1.686) Pub Date : 2020-06-02
    Stefan Kratsch; Magnus WahlströM

    We continue the development of matroid-based techniques for kernelization, initiated by the present authors [47]. We significantly extend the usefulness of matroid theory in kernelization by showing applications of a result on representative sets due to Lovász [51] and Marx [53]. As a first result, we show how representative sets can be used to derive a polynomial kernel for the elusive ALMOST 2-SAT

  • Fully Online Matching
    J. ACM (IF 1.686) Pub Date : 2020-05-13
    Zhiyi Huang; Ning Kang; Zhihao Gavin Tang; Xiaowei Wu; Yuhao Zhang; Xue Zhu

    We introduce a fully online model of maximum cardinality matching in which all vertices arrive online. On the arrival of a vertex, its incident edges to previously arrived vertices are revealed. Each vertex has a deadline that is after all its neighbors’ arrivals. If a vertex remains unmatched until its deadline, then the algorithm must irrevocably either match it to an unmatched neighbor or leave

  • A Near-linear Time ε-Approximation Algorithm for Geometric Bipartite Matching
    J. ACM (IF 1.686) Pub Date : 2020-06-17
    Sharath Raghvendra; Pankaj K. Agarwal

    For point sets A, B ⊂ Rd, ∣A∣ = ∣B∣ = n, and for a parameter ε > 0, we present a Monte Carlo algorithm that computes, in O(npoly(log n, 1/ε)) time, an ε-approximate perfect matching of A and B under any Lp-norm with high probability; the previously best-known algorithm takes Ω(n3/2) time. We approximate the Lp-norm using a distance function, d(⋅, ⋅) based on a randomly shifted quad-tree. The algorithm

  • Embeddability in R3is NP-hard
    J. ACM (IF 1.686) Pub Date : 2020-06-04
    Arnaud de Mesmay; Yo’av Rieck; Eric Sedgwick; Martin Tancer

    We prove that the problem of deciding whether a two- or three-dimensional simplicial complex embeds into R3 is NP-hard. Our construction also shows that deciding whether a 3-manifold with boundary tori admits an S3 filling is NP-hard. The former stands in contrast with the lower-dimensional cases, which can be solved in linear time, and the latter with a variety of computational problems in 3-manifold

  • Scene Grammars, Factor Graphs, and Belief Propagation
    J. ACM (IF 1.686) Pub Date : 2020-05-30
    Jeroen Chua; Pedro F. Felzenszwalb

    We describe a general framework for probabilistic modeling of complex scenes and for inference from ambiguous observations. The approach is motivated by applications in image analysis and is based on the use of priors defined by stochastic grammars. We define a class of grammars that capture relationships between the objects in a scene and provide important contextual cues for statistical inference

  • Planar Graph Perfect Matching Is in NC
    J. ACM (IF 1.686) Pub Date : 2020-05-30
    Nima Anari; Vijay V. Vazirani

    Is perfect matching in NC? That is, is there a deterministic fast parallel algorithm for it? This has been an outstanding open question in theoretical computer science for over three decades, ever since the discovery of RNC perfect matching algorithms. Within this question, the case of planar graphs has remained an enigma: On the one hand, counting the number of perfect matchings is far harder than

  • Deterministic Factorization of Sparse Polynomials with Bounded Individual Degree
    J. ACM (IF 1.686) Pub Date : 2020-05-09
    Vishwas Bhargava; Shubhangi Saraf; Ilya Volkovich

    In this article, we study the problem of deterministic factorization of sparse polynomials. We show that if f ∈ F[x1,x2,… ,xn] is a polynomial with s monomials, with individual degrees of its variables bounded by d, then f can be deterministically factored in time spoly(d)log n. Prior to our work, the only efficient factoring algorithms known for this class of polynomials were randomized, and other

  • A Simpler and Faster Strongly Polynomial Algorithm for Generalized Flow Maximization
    J. ACM (IF 1.686) Pub Date : 2020-05-09
    Neil Olver; László A. Végh

    We present a new strongly polynomial algorithm for generalized flow maximization that is significantly simpler and faster than the previous strongly polynomial algorithm [34]. For the uncapacitated problem formulation, the complexity bound O(mn(m+n log n)log (n2/m)) improves on the previous estimate by almost a factor O(n2). Even for small numerical parameter values, our running time bound is comparable

  • Frege Systems for Quantified Boolean Logic
    J. ACM (IF 1.686) Pub Date : 2020-05-09
    Olaf Beyersdorff; Ilario Bonacina; Leroy Chew; Jan Pich

    We define and investigate Frege systems for quantified Boolean formulas (QBF). For these new proof systems, we develop a lower bound technique that directly lifts circuit lower bounds for a circuit class C to the QBF Frege system operating with lines from C. Such a direct transfer from circuit to proof complexity lower bounds has often been postulated for propositional systems but had not been formally

  • A Simple Deterministic Distributed MST Algorithm with Near-Optimal Time and Message Complexities
    J. ACM (IF 1.686) Pub Date : 2020-05-09
    M. Elkin

    The distributed minimum spanning tree (MST) problem is one of the most central and fundamental problems in distributed graph algorithms. Kutten and Peleg devised an algorithm with running time O(D + √n ⋅ log* n), where D is the hop diameter of the input n-vertex m-edge graph, and with message complexity O(m + n3/2). Peleg and Rubinovich showed that the running time of the algorithm of Kutten and Peleg

  • Polynomial Counting in Anonymous Dynamic Networks with Applications to Anonymous Dynamic Algebraic Computations
    J. ACM (IF 1.686) Pub Date : 2020-05-09
    Dariusz R. Kowalski; Miguel A. Mosteiro

    Starting with with work of Michail et al., the problem of Counting the number of nodes in Anonymous Dynamic Networks has attracted a lot of attention. The problem is challenging because nodes are indistinguishable (they lack identifiers and execute the same program), and the topology may change arbitrarily from round to round of communication, as long as the network is connected in each round. The

  • Matrix Multiplication, a Little Faster
    J. ACM (IF 1.686) Pub Date : 2020-04-05
    Elaye Karstadt; Oded Schwartz

    Strassen’s algorithm (1969) was the first sub-cubic matrix multiplication algorithm. Winograd (1971) improved the leading coefficient of its complexity from 6 to 7. There have been many subsequent asymptotic improvements. Unfortunately, most of these have the disadvantage of very large, often gigantic, hidden constants. Consequently, Strassen-Winograd’s O(nlog27) algorithm often outperforms other fast

  • Silence
    J. ACM (IF 1.686) Pub Date : 2020-04-05
    Guy Goren; Yoram Moses

    The cost of communication is a substantial factor affecting the scalability of many distributed applications. Every message sent can incur a cost in storage, computation, energy, and bandwidth. Consequently, reducing the communication costs of distributed applications is highly desirable. The best way to reduce message costs is by communicating without sending any messages whatsoever. This article

  • Approximating Generalized Network Design under (Dis)economies of Scale with Applications to Energy Efficiency
    J. ACM (IF 1.686) Pub Date : 2020-04-05
    Yuval Emek; Shay Kutten; Ron Lavi; Yangguang Shi

    In a generalized network design (GND) problem, a set of resources are assigned (non-exclusively) to multiple requests. Each request contributes its weight to the resources it uses and the total load on a resource is then translated to the cost it incurs via a resource-specific cost function. Motivated by energy efficiency applications, recently, there is a growing interest in GND using cost functions

  • Fully Functional Suffix Trees and Optimal Text Searching in BWT-Runs Bounded Space
    J. ACM (IF 1.686) Pub Date : 2020-04-05
    Travis Gagie; Gonzalo Navarro; Nicola Prezza

    Indexing highly repetitive texts—such as genomic databases, software repositories and versioned text collections—has become an important problem since the turn of the millennium. A relevant compressibility measure for repetitive texts is r, the number of runs in their Burrows-Wheeler Transforms (BWTs). One of the earliest indexes for repetitive collections, the Run-Length FM-index, used O(r) space

  • Differential Equation Invariance Axiomatization
    J. ACM (IF 1.686) Pub Date : 2020-04-05
    André Platzer; Yong Kiam Tan

    This article proves the completeness of an axiomatization for differential equation invariants described by Noetherian functions. First, the differential equation axioms of differential dynamic logic are shown to be complete for reasoning about analytic invariants. Completeness crucially exploits differential ghosts, which introduce additional variables that can be chosen to evolve freely along new

  • Foundations of Context-aware Preference Propagation
    J. ACM (IF 1.686) Pub Date : 2020-04-05
    Paolo Ciaccia; Davide Martinenghi; Riccardo Torlone

    Preferences are a fundamental ingredient in a variety of fields, ranging from economics to computer science, for deciding the best choices among possible alternatives. Contexts provide another important aspect to be considered in the selection of the best choices, since, very often, preferences are affected by context. In particular, the problem of preference propagation from more generic to more specific

  • Detecting an Odd Hole
    J. ACM (IF 1.686) Pub Date : 2020-04-05
    Maria Chudnovsky; Alex Scott; Paul Seymour; Sophie Spirkl

    We give a polynomial-time algorithm to test whether a graph contains an induced cycle with length more than three and odd.

  • An Unrestricted Learning Procedure
    J. ACM (IF 1.686) Pub Date : 2019-12-06
    Shahar Mendelson

    We study learning problems involving arbitrary classes of functions F, underlying measures μ, and targets Y. Because proper learning procedures, i.e., procedures that are only allowed to select functions in F, tend to perform poorly unless the problem satisfies some additional structural property (e.g., that F is convex), we consider unrestricted learning procedures that are free to choose functions

  • The Weisfeiler--Leman Dimension of Planar Graphs Is at Most 3
    J. ACM (IF 1.686) Pub Date : 2019-12-06
    Sandra Kiefer; Ilia Ponomarenko; Pascal Schweitzer

    We prove that the Weisfeiler--Leman (WL) dimension of the class of all finite planar graphs is at most 3. In particular, every finite planar graph is definable in first-order logic with counting using at most 4 variables. The previously best-known upper bounds for the dimension and number of variables were 14 and 15, respectively. First, we show that, for dimension 3 and higher, the WL-algorithm correctly

  • Tight Bounds for Undirected Graph Exploration with Pebbles and Multiple Agents
    J. ACM (IF 1.686) Pub Date : 2019-12-06
    Yann Disser; Jan Hackfeld; Max Klimm

    We study the problem of deterministically exploring an undirected and initially unknown graph with n vertices either by a single agent equipped with a set of pebbles or by a set of collaborating agents. The vertices of the graph are unlabeled and cannot be distinguished by the agents, but the edges incident to a vertex have locally distinct labels. The graph is explored when all vertices have been

  • Invited Articles Foreword
    J. ACM (IF 1.686) Pub Date : 2019-12-06
    Eva Tardos

    The Invited Articles section of this issue consists of two articles. The article “The WeisfeilerLeman Dimension of Planar Graphs is at most 3,” by Sandra Kiefer, Ilia Ponomarenko, and Pascal Schweitzer, was invited from the 32nd Annual ACM/ IEEE Symposium on Logic in Computer Science (LICS’17). The article “Computing the Geometric Intersection Number of Curves,” by Vincent Despré and Francis Lazarus

  • Deciding Context Unification
    J. ACM (IF 1.686) Pub Date : 2019-12-06
    Artur Jeż

    In first-order term unification, variables represent well-formed terms over a given signature, and we are to solve equations built using function symbols from the signature and such variables; this problem is well-known to be decidable (in linear time). In second-order term unification, the variables take arguments (i.e., other terms) and a substitution uses those arguments an arbitrary number of times;

  • On the Complexity of Cache Analysis for Different Replacement Policies
    J. ACM (IF 1.686) Pub Date : 2019-12-06
    David Monniaux; Valentin Touzeau

    Modern processors use cache memory, a memory access that “hits” the cache returns early, while a “miss” takes more time. Given a memory access in a program, cache analysis consists in deciding whether this access is always a hit, always a miss, or is a hit or a miss depending on execution. Such an analysis is of high importance for bounding the worst-case execution time of safety-critical real-time

  • White-Box vs. Black-Box Complexity of Search Problems
    J. ACM (IF 1.686) Pub Date : 2019-09-28
    Ilan Komargodski; Moni Naor; Eylon Yogev

    Ramsey theory assures us that in any graph there is a clique or independent set of a certain size, roughly logarithmic in the graph size. But how difficult is it to find the clique or independent set? If the graph is given explicitly, then it is possible to do so while examining a linear number of edges. If the graph is given by a black-box, where to figure out whether a certain edge exists the box

  • Self-Stabilising Byzantine Clock Synchronisation Is Almost as Easy as Consensus
    J. ACM (IF 1.686) Pub Date : 2019-09-28
    Christoph Lenzen; Joel Rybicki

    We give fault-tolerant algorithms for establishing synchrony in distributed systems in which each of the n nodes has its own clock. Our algorithms operate in a very strong fault model: we require self-stabilisation, i.e., the initial state of the system may be arbitrary, and there can be up to f< n/3 ongoing Byzantine faults, i.e., nodes that deviate from the protocol in an arbitrary manner. Furthermore

  • Online Bipartite Matching with Amortized O(log 2 n) Replacements
    J. ACM (IF 1.686) Pub Date : 2019-09-28
    Aaron Bernstein; Jacob Holm; Eva Rotenberg

    In the online bipartite matching problem with replacements, all the vertices on one side of the bipartition are given, and the vertices on the other side arrive one-by-one with all their incident edges. The goal is to maintain a maximum matching while minimizing the number of changes (replacements) to the matching. We show that the greedy algorithm that always takes the shortest augmenting path from

  • Index Reduction for Differential-algebraic Equations with Mixed Matrices
    J. ACM (IF 1.686) Pub Date : 2019-09-28
    Satoru Iwata; Taihei Oki; Mizuyo Takamatsu

    Differential-algebraic equations (DAEs) are widely used for the modeling of dynamical systems. The difficulty in numerically solving a DAE is measured by its differentiation index. For highly accurate simulation of dynamical systems, it is important to convert high-index DAEs into low-index DAEs. Most of the existing simulation software packages for dynamical systems are equipped with an index-reduction

  • On the Parameterized Complexity of Approximating Dominating Set
    J. ACM (IF 1.686) Pub Date : 2019-09-28
    Karthik C. S.; Bundit Laekhanukit; Pasin Manurangsi

    We study the parameterized complexity of approximating the k-Dominating Set (DomSet) problem where an integer k and a graph G on n vertices are given as input, and the goal is to find a dominating set of size at most F(k) ⋅ k whenever the graph G has a dominating set of size k. When such an algorithm runs in time T(k) ⋅ poly (n) (i.e., FPT-time) for some computable function T, it is said to be an

  • An Operational Characterization of Mutual Information in Algorithmic Information Theory
    J. ACM (IF 1.686) Pub Date : 2019-09-28
    Andrei Romashchenko; Marius Zimand

    We show that the mutual information, in the sense of Kolmogorov complexity, of any pair of strings x and y is equal, up to logarithmic precision, to the length of the longest shared secret key that two parties—one having x and the complexity profile of the pair and the other one having y and the complexity profile of the pair—can establish via a probabilistic protocol with interaction on a public channel

Contents have been reproduced by permission of the publishers.
Springer 纳米技术权威期刊征稿
ACS ES&T Engineering
ACS ES&T Water