Henzinger et al. posed the so-called Online Boolean Matrix-vector Multiplication (OMv) conjecture and showed that it implies tight hardness results for several basic dynamic or partially dynamic problems [STOC'15]. We first show that the OMv conjecture is implied by a simple off-line conjecture that we call the MvP conjecture. We then show that if the definition of the OMv conjecture is generalized

The degree distribution of an ordered tree T with n nodes is n→=(n0,…,nn−1), where ni is the number of nodes in T with i children. Let N(n→) be the number of trees with degree distribution n→. We give a data structure that stores an ordered tree T with n nodes and degree distribution n→ using log⁡N(n→)+O(n/logt⁡n) bits for every constant t. The data structure answers tree queries in constant time.

In this paper we characterize normal sequences and finite-state dimension in terms of the automatic Kolmogorov complexity and finite-state a priori probability. We show that many known results about normal sequences and finite-state dimension, including the equivalence between aligned and non-aligned normality, Wall's theorem, Piatetski–Shapiro's theorem, Champernowne's example of normal number and

In this paper, we study the Maximum Internal Spanning Tree Problem (MIST). Given an undirected simple graph G, the task for the Maximum Internal Spanning Tree problem is to find a spanning tree of G with maximum number of internal vertices. We present an approximation algorithm with performance ratio 43, which improves upon the best known performance ratio 32. Our algorithm benefits from a new observation

The expensive cost and intermittent availability of renewable energy bring great challenges to its efficient utilization in green data centers. In this paper, we propose a new way to achieve an explicit trade-off between operational cost and carbon emission by dynamic storing off-site renewable energy in distributed data centers. We first formulate a constrained stochastic optimization problem for

Let a text T[1..n] be the only string generated by a context-free grammar with g (terminal and nonterminal) symbols, and of size G (measured as the sum of the lengths of the right-hand sides of the rules). Such a grammar, called a grammar-compressed representation of T, can be encoded using Glg⁡G bits. We introduce the first grammar-compressed index that uses O(Glg⁡n) bits (precisely, Glg⁡n+(2+ϵ)Glg⁡g

It is well known that hyperedge-replacement grammars can generate NP-complete graph languages even under seemingly harsh restrictions. This means that the parsing problem is difficult even in the non-uniform setting, in which the grammar is considered to be fixed rather than being part of the input. Little is known about restrictions under which truly uniform polynomial parsing is possible. In this

The modularity is the best known and widely used quality function for community detection in graphs. We investigate the approximability of the modularity maximization problem and some related problems. We first design a polynomial-time 0.4209-additive approximation algorithm for the modularity maximization problem, which improves the current best additive approximation error of 0.4672. Our theoretical

Maximum parsimony distance is a measure used to quantify the dissimilarity of two unrooted phylogenetic trees. It is NP-hard to compute, and very few positive algorithmic results are known due to its complex combinatorial structure. Here we address this shortcoming by showing that the problem is fixed parameter tractable. We do this by establishing a linear kernel i.e., that after applying certain

Timed pushdown automata (tpda) are an expressive formalism combining recursion with a rich logic of timing constraints. We prove that reachability relations of tpda are expressible in linear arithmetic, a rich logic generalising Presburger arithmetic and rational arithmetic. The main technical ingredients are a novel quantifier elimination result for clock constraints (used to simplify the syntax of

We study the problem of counting the repairs of an inconsistent database in the case where constraints are Functional Dependencies (FDs). A repair is then a maximal independent set of the conflict graph, wherein nodes represent facts and edges represent violations. We establish a dichotomy in data complexity for the complete space of FDs: when the FD set has, up to equivalence, what we call a “left-hand-side

The main contributions of the paper are summarized as follows. We take an analytical approach in the sense that the quality of service and the price of service as well as the revenue, cost, and profit of a cloud service provider (CSP) can all be quantitatively available based on well established analytical models. We argue that the satisfaction of a customer includes two aspects, i.e., satisfaction

We study selective monitors for labelled Markov chains. Monitors observe the outputs that are generated by a Markov chain during its run, with the goal of identifying runs as correct or faulty. A monitor is selective if it skips observations in order to reduce monitoring overhead. We are interested in monitors that minimize the expected number of observations. We establish an undecidability result

In k-Clustering we are given a multiset of n vectors X⊂Zd and a nonnegative number D, and we need to decide whether X can be partitioned into k clusters C1,…,Ck such that the cost∑i=1kminci∈Rd⁡∑x∈Ci‖x−ci‖pp≤D, where ‖⋅‖p is the Lp-norm. For p=2, k-Clustering is k-Means. We study k-Clustering from the perspective of parameterized complexity. The problem is known to be NP-hard for k=2 and also for d=2

We study the problem of finding an exact solution to the Consensus Halving problem. While recent work has shown that the approximate version of this problem is PPA -complete [29], [30], we show that the exact version is much harder. Specifically, finding a solution with n agents and n cuts is FIXP -hard, and deciding whether there exists a solution with fewer than n cuts is ETR -complete. Along the

Let string S[1..n] be parsed into z phrases by the Lempel-Ziv algorithm. The corresponding compression algorithm encodes S in O(z) space, but it does not support random access to S. We introduce a data structure, the block tree, that represents S in O(zlog⁡(n/z)) space and extracts any symbol of S in time O(log⁡(n/z)), among other space-time tradeoffs. The structure also supports other queries that

The inverse satisfiability problem over a set of relations Γ (Inv-SAT(Γ)) is the problem of deciding whether a relation R can be defined as the set of models of a SAT(Γ) instance. Kavvadias and Sideri (1998) [15] obtained a dichotomy between P and co-NP-complete for finite Γ containing the two constant Boolean relations. However, for arbitrary constraint languages the complexity has been wide open

We consider weighted congestion games with polynomial latency functions of maximum degree d≥1. For these games, we investigate the existence and efficiency of approximate pure Nash equilibria which are obtained through sequences of unilateral improvement moves by the players. By exploiting a simple technique, we firstly show that these games admit an infinite set of d-approximate potential functions

In 2003, Fischlin introduced the concept of progressive verification in cryptography to relate the error probability of a cryptographic verification procedure to its running time. It ensures that the verifier confidence in the validity of a verification procedure grows with the work it invests in the computation. Le, Kelkar and Kate recently revisited this approach for digital signatures and proposed

In this paper, we introduce the model of quantum Mealy machines and study the equivalence checking and minimisation problems of them. Two efficient algorithms are developed for checking equivalence of two states in the same machine and for checking equivalence of two machines. As an application, they are used in equivalence checking of quantum circuits. Moreover, the minimisation problem is proved

A family of tree automata of size n is presented such that the size of the largest common prefix (lcp) tree of all accepted trees is exponential in n. Moreover, it is shown that this prefix tree is not compressible via DAGs (directed acyclic graphs) or tree straight-line programs. We also show that determining whether or not the lcp trees of two given tree automata are equal is coNP-complete; the result

We study two problems where k autonomous mobile agents are initially located on distinct nodes of a weighted graph with n nodes and m edges. Each agent has a predefined velocity and can only move along the edges of the graph. The first problem is to deliver one package from a source node to a destination node. The second is to simultaneously deliver two packages, each from its source node to its destination

We study the complexity of #CSPΔ(Γ), which is the problem of counting satisfying assignments to CSP instances with constraints from Γ and whose variables can appear at most Δ times. Our main result shows that: (i) if every function in Γ is affine, then #CSPΔ(Γ) is in FP for all Δ, (ii) otherwise, if every function in Γ is in a class called IM2, then for large Δ, #CSPΔ(Γ) is equivalent under approximation-preserving

Given a subset of states S of a deterministic finite automaton and a word w, the preimage is the subset of all states mapped to a state in S by the action of w. We study three natural problems concerning words giving certain preimages. The first problem is whether, for a given subset, there exists a word extending the subset (giving a larger preimage). The second problem is whether there exists a totally

Temporal graphs (in which edges are active at specified times) are of particular relevance for spreading processes on graphs, e.g. the spread of disease or dissemination of information. Motivated by real-world applications, modification of static graphs to control this spread has proven a rich topic for previous research. Here, we introduce a new type of modification for temporal graphs: the number

This work studies multi-broadcasting for the SINR (Signal-to-Interference-plus-Noise-Ratio) model, assuming a subset of nodes are initially awake, when each device only has access to knowledge about the total number of nodes in the network n, the range from which each node's label is taken {1,…,N}, and the label of the device itself. We assume no knowledge of the physical coordinates of devices and

We show that computation of the SPERNER problem is PPA-complete on the Möbius band under proper boundary conditions, settling a long term open problem. Further, the same computational complexity results extend to other discrete fixed points on the Möbius band, such as the Brouwer fixed point problem, the DPZP fixed point problem and a simple version of the Tucker problem, as well as the projective

We consider a family of skew tent maps fa on the unit interval, determined by the parameter a, with 0

A decidability proof for bisimulation equivalence of first-order grammars is given. It is an alternative proof for a result by Sénizergues (1998, 2005) that subsumes his affirmative solution of the famous decidability question for deterministic pushdown automata. The presented proof is conceptually simpler, and a particular novelty is that it is not given as two semidecision procedures but it provides

We consider the circular pattern matching with k mismatches (k-CPM) problem in which one is to compute the minimal Hamming distance of every length-m substring of T and any cyclic rotation of P, if this distance is no more than k. It is a variation of the well-studied k-mismatch problem. A multitude of papers has been devoted to solving the k-CPM problem, but only average-case upper bounds are known

Edge fault-tolerance of interconnection network is of significant important to the design and maintenance of multiprocessor systems. A connected graph G is maximally edge-connected (maximally-λ for short) if its edge-connectivity attains its minimum degree. G is super edge-connected (super-λ for short) if every minimum edge-cut isolates one vertex. The edge fault-tolerance of the maximally-λ (resp

Let M=(T,C,P) be a security model, where T is a rooted tree, C is a multiset of costs and P is a multiset of prizes and let (T,c,p) be a security system, where c and p are bijections of costs and prizes. The problems of computing an optimal attack on a security system and of determining an edge e∈E(T) such that the maximum sum of prizes obtained from an optimal attack in (T,c,p) is minimized when c(e)=∞

In this work we introduce and study a pursuit-evasion game in which the search is performed by heterogeneous entities. We incorporate heterogeneity into the classical edge search problem by considering edge-labeled graphs: once a search strategy initially assigns labels to the searchers, each searcher can be only present on an edge of its own label. We prove that this problem is not monotone even for

Message sequence charts (MSCs) naturally arise as executions of communicating finite-state machines (CFMs), in which finite-state processes exchange messages through unbounded FIFO channels. We study the first-order logic of MSCs, featuring Lamport's happened-before relation. To this end, we introduce a star-free version of propositional dynamic logic (PDL) with loop and converse. Our main results

The Cayley table representation of a group uses O(n2) words for a group of order n and answers multiplication queries in time O(1). It is interesting to ask if there is a o(n2) space representation of groups that still has O(1) query-time. We show that for any δ, 1/log⁡n≤δ≤1, there is an O(n1+δ/δ) space representation for groups of order n with O(1/δ) query-time. We also show that for Dedekind groups

We study the expressive power of 1-way data-independent finite automata with k heads (1DiDFA(k)). The data-independence means that the trajectory of each head during a computation depends only on the length of the input word. It has long been known that “k+1 heads are better than k” for the (data-dependent) 1DFA(k), and (2-way) 2DiDFA(k). However, somewhat surprisingly, no such hierarchy has been known

In public key encryption with keyword search (PEKS), a secure channel is required in order to send trapdoors to the server, whereas in secure-channel free PEKS (SCF-PEKS), no such secure channel is required. In this paper, we propose a generic construction of SCF-PEKS with multiple keywords (SCF-MPEKS) from hidden vector encryption, tag-based encryption, and a one-time signature. Our generic construction

Galled trees are studied as a recombination model in population genetics. This class of phylogenetic networks is generalized into tree-child and galled network classes by relaxing a structural condition imposed on galled trees. We provide a solution to an open problem that is how to count and enumerate tree-child networks with fixed number of leaves and reticulations. Explicit counting formulas are

We study stability of routing in multi-hop wireless networks in the framework of adversarial queueing. A routing algorithm consists of three components: a transmission policy to decide on immediate transmissions, a scheduling policy to select a packet to transmit, and a hearing control to coordinate transmissions with scheduling. We consider two kinds of hearing control: proactive and reactive. We

The complexity class CLS was proposed by Daskalakis and Papadimitriou in 2011 to understand the complexity of important NP search problems that admit both path following and potential optimizing algorithms. Here we identify a subclass of CLS – called UniqueEOPL – that applies a more specific combinatorial principle that guarantees unique solutions. We show that UniqueEOPL contains several important

Temporal graphs abstractly model real-life inherently dynamic networks. Given a graph G, a temporal graph with G as the underlying graph is a sequence of subgraphs (snapshots) Gt of G, where t≥1. In this paper we study stochastic temporal graphs, i.e. stochastic processes G whose random variables are the snapshots of a temporal graph on G. A natural feature observed in various real-life scenarios is

We study the question of finding a set of at most k edges, whose removal makes the input n-vertex graph a disjoint union of s-clubs (graphs of diameter s). Komusiewicz and Uhlmann [DAM 2012] showed that Cluster Edge Deletion (i.e., for the case of 1-clubs (cliques)), cannot be solved in time 2o(k)nO(1) unless the Exponential Time Hypothesis (ETH) fails. But, Fomin et al. [JCSS 2014] showed that if

This paper studies the problem of finding a path center on a tree in which vertex weights are uncertain and the uncertainty is described by given intervals. It is required to find a minmax regret solution, which minimizes the worst-case loss in the objective function. An O(n log n)-time algorithm is presented, improving the previous upper bound of O(n2).

Problems related to finding induced subgraphs satisfying given properties form one of the most studied areas within graph algorithms. However, for many applications, it is desirable that the found subgraph has as few connections to the rest of the graph as possible, which gives rise to the Secluded Π-Subgraph problem. Here, input k is the size of the desired subgraph, and input t is a limit on the

A treasure is placed in one of M boxes according to a known distribution and k searchers are searching for it in parallel during T rounds. How can one incentivize selfish players so that the probability that at least one player finds the treasure is maximized? We focus on congestion policies C(ℓ) specifying the reward a player receives being one of the ℓ players that (simultaneously) find the treasure

Translocation has been long learned as a basic operation to rearrange the structure of a genome. Translocation sorting asks to find a shortest sequence of translocations that transforms one genome into another, which has attracted attention of many scientists in algorithm design. Signed translocation sorting can be solved in polynomial time. Unsigned translocation sorting turns out to be NP-Hard and

We provide a counterexample to a conjecture by Thiagarajan (1996, 2002) that regular event structures correspond to event structures obtained as unfoldings of finite 1-safe Petri nets. The same counterexample is used to disprove a closely related conjecture by Badouel, Darondeau, and Raoult (1999). Using that domains of events structures are CAT(0) cube complexes, we construct our counterexample from

A disconnected cut of a connected graph is a vertex cut that itself also induces a disconnected subgraph. The corresponding decision problem is called Disconnected Cut. This problem is known to be NP-hard on general graphs. We prove that it is polynomial-time solvable on claw-free graphs, answering a question of Ito et al. (TCS 2011). The basis for our result is a decomposition theorem for claw-free

In this paper we study the reconstruction problem in the congested clique model. Given a class of graphs G, the problem is defined as follows: if G∉G, then every node must reject; if G∈G, then every node must end up knowing all the edges of G. The cost of an algorithm is the total number of bits received by any node through one link. It is not difficult to see that the cost of any algorithm that solves

Operator Precedence Languages (OPL) are deterministic context-free and have desirable properties. OPL are parallely parsable, and, when structurally compatible, are closed under Boolean operations, concatenation and star; they include the Input Driven languages. OPL use three relations between two terminal symbols, to assign syntax structure to words. We extend such relations to k-tuples of consecutive

The k-dimensional Weisfeiler-Leman algorithm (k-WL) is a fruitful approach to the Graph Isomorphism problem. 2-WL corresponds to the original algorithm suggested by Weisfeiler and Leman over 50 years ago. 1-WL is the classical color refinement routine. Indistinguishability by k-WL is an equivalence relation on graphs that is of fundamental importance for isomorphism testing, descriptive complexity

We introduce a new framework for a descriptive complexity approach to arithmetic computations. We define a hierarchy of classes based on the idea of counting assignments to free function variables in first-order formulae. We completely determine the inclusion structure and show that and appear as classes of this hierarchy. In this way, we unconditionally place properly in a strict hierarchy of arithmetic

To obtain a high-speed IP address lookup algorithm for wire-speed packet forwarding in Internet routers, a new data structure, called multilevel length-based classified index table, is proposed. This data structure can be divided into multilevel structures on the basis of prefix length distribution. Each level has a corresponding data structure and dynamic router-table operations. Experiments were

A graph G=(V,E) is δ-hyperbolic if for any four vertices u,v,w,x, the two larger of the three distance sums d(u,v)+d(w,x), d(u,w)+d(v,x), d(u,x)+d(v,w) differ by at most 2δ≥0. This paper describes the eccentricity terrain of a δ-hyperbolic graph. The eccentricity function eG(v)=max⁡{d(v,u):u∈V} partitions vertices of G into eccentricity layers Ck(G)={v∈V:eG(v)=rad(G)+k}, k∈N, where rad(G)=min⁡{eG(v):v∈V}

We investigate a distributed maximal independent set reconfiguration problem, in which there are two MIS for which every node is given its membership status, and the nodes need to communicate with their neighbors to find a reconfiguration schedule from the first MIS to the second. We forbid two neighbors to change their membership status at the same step. We provide efficient solutions when the intermediate

Bin packing with cardinality constraints is a basic bin packing problem. In the online version with the parameter k≥2, items having sizes in (0,1] associated with them are presented one by one to be packed into unit capacity bins, such that the capacities of bins are not exceeded, and no bin receives more than k items. We resolve the online problem and prove a lower bound of 2 on the overall asymptotic

Probabilistic bisimilarity, due to Segala and Lynch, is an equivalence relation that captures which states of a probabilistic automaton behave exactly the same. Deng et al. proposed a robust quantitative generalization of probabilistic bisimilarity. Their probabilistic bisimilarity distances of states of a probabilistic automaton capture the similarity of their behaviour. The smaller the distance,

We show that structures with only one binary function symbol are universal for “online” (punctual) computable structures. In contrast, we give a description of punctually categorical graphs which implies that graphs are not universal for online computability.

The task of aggregating individual judgments over logically interconnected propositions is called judgment aggregation. Manipulation of judgment aggregation procedures has first been studied by List [45] and Dietrich and List [27], and Endriss et al. [30] were the first to study it from a computational perspective. Baumeister et al. [7] extended their results on manipulation and introduced the concept

We consider threshold group testing – a generalization of group testing, which asks to identify a set of positive individuals in a population, by performing tests on pools of elements. Each test is represented by a subset Q of individuals and its output is yes if Q contains at least one positive element and no otherwise. Threshold group testing is the natural generalization, introduced by P. Damaschke