Prior-free auctions are robust auctions that assume no distribution over bidders' valuations and provide worst-case (input-by-input) approximation guarantees. In contrast to previous work on this topic, we pursue good prior-free auctions with non-identical bidders. Prior-free auctions can approximate meaningful benchmarks for non-identical bidders only when sufficient qualitative information about

Building a trustworthy life-critical embedded system requires deep reasoning about the potential effects that sequences of machine instructions can have on full system operation. Rather than trying to analyze complete binaries and the countless ways their instructions can interact with one another — memory, side effects, control registers, implicit state, etc. — we explore a new approach. We propose

Pudlák [14] lists several major complexity theoretic conjectures relevant to proof complexity and asks for oracles that separate pairs of corresponding relativized conjectures. Among these conjectures are: • CON and SAT: coNP (resp., NP) does not contain many-one complete sets that have P-optimal proof systems. • NP∩coNP: NP∩coNP does not have many-one complete problems. • P≠NP. We construct two of

In the Maximum-Duo Preservation String Mapping (Max-Duo PSM) problem, the input consists of two related strings A and B of length n and a nonnegative integer k. The objective is to determine whether there exists a mapping m from the set of positions of A to the set of positions of B that maps only to positions with the same character and preserves at least k duos, which are pairs of adjacent positions

The connectivity of a graph is an important issue in graph theory and is also one of the most important factors in evaluating the reliability and fault tolerance of a network. A graph G is called m-edge-fault-tolerant strongly Menger(m-EFTSM for short) edge connected if there are min⁡{degG−F⁡(x),degG−F⁡(y)} edge-disjoint paths between any two different vertices x and y in G−F for any F⊆E(G) with |F|≤m

We study the descending facility location (DFL) problem on the surface of a triangulated terrain. A path from a point s to a point t on the surface of a terrain is descending if the heights of the subsequent points along the path from s to t are in a monotonically non-increasing order [1]. We are given a set D={d1,d2,⋯,dn} of n demand points on the surface of a triangulated terrain W and our objective

Spectral techniques have proved amongst the most effective approaches to graph clustering. However, in general they require explicit computation of the main eigenvectors of a suitable matrix (usually the Laplacian matrix of the graph). Recent work (e.g., Becchetti et al., SODA 2017) suggests that observing the temporal evolution of the power method applied to an initial random vector may, at least

This paper considers the one-cop-moves game played on a graph. In this game, a set of cops and a robber occupy the vertices of the graph and move alternately along the graph's edges with perfect information about each other's positions. The goal of the cops is to capture the robber. At cops' turns, exactly one cop is allowed to move from his location to an adjacent vertex; at robber's turns, she is

We argue that proven exponential upper bounds on runtimes, an established area in classic algorithms, are interesting also in heuristic search and we prove several such results. We show that any of the algorithms randomized local search, Metropolis algorithm, simulated annealing, and (1+1) evolutionary algorithm can optimize any pseudo-Boolean weakly monotonic function under a large set of noise assumptions

We study a Curry style type assignment system for untyped λ-calculi with effects, based on Moggi's monadic approach. Moving from the abstract definition of monads, we introduce a version of the call-by-value computational λ-calculus based on Wadler's variant, without let, and with unit and bind operators. We define a notion of reduction for the calculus and prove it confluent. We then introduce an

We establish new results on the curve complexity of k-colored point-set embeddings when k=3. We show that there exist 3-colored caterpillars with only three independent edges whose 3-colored point-set embeddings may require Ω(n13) bends on Ω(n23) edges. This settles an open problem by Badent et al. [5] about the curve complexity of point set embeddings of k-colored trees and it extends a lower bound

A fan is a set of edges with a single common endpoint. A drawing of a graph in the plane is fan-crossing if each edge can only be crossed by edges of a fan. It is fan-planar if, in addition, the common endpoint is on the same side of the crossed edge. A drawing is adjacency-crossing if any two edges are adjacent if they cross the same edge. Then multiple independent crossings are excluded, in which

We study the problem of exploration by a mobile entity (agent) of a class of highly dynamic networks, namely the carrier graphs (the C-graphs, modeling public transportation systems, among others). These are defined by a set of carriers following infinitely their prescribed route along the stations of the network. Flocchini, Mans, and Santoro [9] studied this problem in the case when the agent must

Partial key exposure attacks on RSA have been intensively studied by using lattice-based Coppersmith's methods. Ernst et al. (Eurocrypt'05) studied the problem by considering three attack scenarios; (1) the most significant bits (MSBs) of a secret exponent d known, (2) the least significant bits (LSBs) of d known, (3) both the MSBs and the LSBs of d known. The proposed attacks were valuable since they

Differential privacy is commonly used in the computer science literature as a mathematical definition of privacy for the purpose of quantifying and bounding privacy loss. It induces a preference order over the set of privacy-jeopardizing mechanisms which, in turn, adhere to some properties of this order. We show that a set of five such properties uniquely captures the ordinal implications of prioritizing

Several relaxations of envy-freeness, tailored to fair division in settings with indivisible goods, have been introduced within the last decade. Due to the lack of general existence results for most of these concepts, great attention has been paid to establishing approximation guarantees. In this work, we propose a simple algorithm that is universally fair in the sense that it returns allocations that

We study the problem of fairly allocating indivisible goods between groups of agents using the recently introduced relaxations of envy-freeness. We consider the existence of fair allocations under different assumptions on the valuations of the agents. In particular, our results cover cases of arbitrary monotonic, responsive, and additive valuations, while for the case of binary valuations we fully

We investigate polynomial-time preprocessing for the problem of hitting forbidden minors in a graph, using the framework of kernelization. For a fixed finite set of connected graphs F, the F-Deletion problem is the following: given a graph G and integer k, is it possible to delete k vertices from G to ensure the resulting graph does not contain any graph from F as a minor? Earlier work by Fomin, Lokshtanov

We study network coordination problems, as captured by the setting of generalized network design (Emek et al., STOC 2018 [18]), in the face of uncertainty resulting from partial information that the network users hold regarding the actions of their peers. This uncertainty is formalized using Alon et al.'s Bayesian ignorance framework (TCS 2012 [1]). While the approach of Alon et al. is purely combinatorial

By using the generating tree technique and the obstinate kernel method, Kim and Lin confirmed a conjecture due to Martinez and Savage which asserts that inversion sequences e=(e1,e2,…,en) containing no three indices iek are counted by Baxter numbers. In this paper, we provide a bijective proof of this conjecture via an intermediate structure of open partition diagrams, in answer to a problem posed

In ACM CCS 2007, Canetti and Hohenberger left an open problem of how to construct a multi-hop unidirectional proxy re-encryption scheme secure against chosen-ciphertext attacks (CCA). To resolve this problem, we utilize the recent advances in indistinguishability obfuscation, overcome several obstacles and propose a multi-hop unidirectional proxy re-encryption scheme. The proposed scheme is proved

Regular language inference, initiated by Angluin, has many developments, including applications in software engineering and testing. However, the capability of finite automata to model the system data is quite limited and, in many cases, extended finite state machine formalisms, that combine the system control with data structures, are used instead. The application of Angluin-style inference algorithms

A non-blocking chromatic tree is a type of balanced binary search tree where multiple processes can concurrently perform search and update operations. We prove that a certain implementation has amortized cost O(c˙+log⁡n) for each operation, where c˙ is the maximum number of concurrent operations during the execution and n is the maximum number of keys in the tree during the operation. This amortized

Self-loop alternating automata (SLAA) with Büchi or co-Büchi acceptance are popular formalisms also known as very weak alternating automata (VWAA). They are often used as an intermediate results in translations of LTL to deterministic or nondeterministic automata. This paper considers SLAA with generic transition-based Emerson-Lei acceptance and presents translations of LTL to these automata and back

We consider the aggregation problem in radio networks: find a spanning tree in a given graph and a conflict-free schedule of the edges so as to minimize the latency of the computation. While a large body of literature exists on this and related problems, we give the first approximation results in graphs that are not induced by unit ranges in the plane. We give a polynomial-time O˜(dn)-approximation

We consider the following basic scheduling problem in wireless networks: partition a given set of unit demand communication links into the minimum number of feasible subsets. A subset is feasible if all communications can be done simultaneously, subject to mutual interference. We use the so-called physical model to formulate feasibility. We consider the two families of approximation algorithms that

We study a class of geometric covering and packing problems for bounded closed regions on the plane. We are given a set of axis-parallel line segments that induce a planar subdivision with bounded (rectilinear) faces. We are interested in the following problems. (P1) Stabbing-Subdivision: Stab all closed bounded faces of the planar subdivision by selecting a minimum number of points in the plane. (P2)

In this paper we consider the problem of maximizing a non-monotone and non-negative DR-submodular function on a bounded integer lattice [B→]={(x1,…,xn)∈Z+n:0≤xk≤Bk,∀1≤k≤n} without any constraint, where B→=(B1,…,Bn)∈Z+n. We design an algorithm for the problem and measure its performance by its approximation ratio and the number of value oracle queries it needs, where the latter one is the dominating

A class of reachability reduction problems were raised in the area of computer network security and software engineering. This paper studies such a reachability reduction problem on a vertex labeled graph. The reachability reduction here is modeled as maximum reachability preserved cut which is a variant of minimum multiway cut with a new objective function. Finding a maximum reachability preserved

Given a database instance and a query on it whose result is initially non-empty, the resilience decision problem is to decide if there exist a small enough number of facts in the database instance such that the deletion of these facts empties the result of the given query. In this paper, we revisit the resilience decision problem. We investigate the parameterized complexity for various classes of database

For graphs F, G and H, let F→(G,H) signify that any red/blue edge coloring of F contains either a red G or a blue H. The Ramsey number R(G,H) is defined as min⁡{r|Kr→(G,H)}. In this note, we consider an optimization problem to bound the complete bipartite-critical Ramsey number RΛ(G,H) defined as max⁡{t|Kr∖Kt,t→(G,H)} where r=R(G,H) and Λ is a set of Kt,t, and determine RΛ(G,H) for some pairs (G,H)

Schedule a mobile charger to replenish energy to sensor nodes for the wireless sensor networks has attracted great attention recently, due to its efficiency and flexibility. Some existing works study the mobile charger scheduling problem by considering that only the depot can recharge or replace the battery for the mobile charger. However, for large-scale wireless sensor networks, the mobile charger

Several formalisms for language syntax specification exist in literature. In this paper, we prove that longstanding syntactical transformations between context-free grammars and algebraic signatures are adjoint functors and/or adjoint equivalences that preserve the abstract syntax of the generated terms. The main result is a categorical equivalence between the categories of algebras (i.e., all the

We consider the problem of learning k-parities in the online mistake-bound model: given a hidden vector x∈{0,1}n where the hamming weight of x is k and a sequence of “questions” a1,a2,…∈{0,1}n, where the algorithm must reply to each question with 〈ai,x〉(mod2), what is the best trade-off between the number of mistakes made by the algorithm and its time complexity? We improve the previous best result

Social networks provide us a convenient platform to communicate and share information or ideas with each other, but it also causes many negative effects at the same time, such as, the spread of misinformation or rumor in social networks may cause public panic and even serious economic or political crisis. In this paper, we propose a Community-based Rumor Blocking Problem (CRBMP), i.e., selecting a

The Almost Induced Matching problem asks whether we can delete at most k vertices from the input graph such that each vertex in the remaining graph has a degree exactly one. This paper studies parameterized algorithms for this problem by taking the size k of the deletion set as the parameter. We give a 7k-vertex kernel and an O⁎(1.7485k)-time and polynomial-space algorithm, both of which are the best-known

In the present study, we provide conditions for the existence of pushouts of signature morphisms in constructor-based order-sorted algebra, and then we prove that reducibility and termination of term rewriting systems are closed under pushouts. Under the termination assumption, reducibility is equivalent to sufficient-completeness, which is crucial for proving several important properties in computing

We introduce and study a new search-type problem with (n+1)-robots on a disk. The searchers (robots) all start from the center of the disk, have unit speed, and can communicate wirelessly. The goal is for a distinguished robot (the queen) to reach and evacuate from an exit that is hidden on the perimeter of the disk in as little time as possible. The remaining n robots (servants) are there to facilitate

Some computations can be elegantly presented as the parallel or simultaneous application of rules. This is the case of cellular automata and of simultaneous assignments in Python. In both cases the expected result cannot be obtained by a sequential application of rules. A general framework of attributed graph transformations is proposed where such computations can be expressed and analyzed. Determinism

The matching preclusion number of a graph, introduced in [2] as a fault analysis, is the minimum number of edges whose deletion leaves a resulting graph that has neither perfect matchings nor almost perfect matchings. As a generalization, Liu and Liu [14] recently introduced the concept of fractional matching preclusion number. The fractional matching preclusion number of graph is the minimum number

It is known for some time that a random graph G(n,p) contains w.h.p. a Hamiltonian cycle if p is larger than the critical value pcrit=(log⁡n+log⁡log⁡n+ωn)/n. The determination of a concrete Hamiltonian cycle for G(n,p) is a nontrivial task, even when p is much larger than pcrit. In this paper we consider random graphs G(n,p) with p in Ω˜(1/n), where Ω˜ hides poly-logarithmic factors in n. For this

A caterpillar is either a K2 or a tree on at least 3 vertices such that deleting its leaves we obtain a path of order at least 1. Given a simple undirected graph G=(V,E), a caterpillar factor of G is a set of caterpillar subgraphs of G such that each vertex v∈V belongs to exactly one of them. A caterpillar factor F is internally even if every vertex of degree degF(v)≥2 has an even degree; F is odd

In the fast evacuation problem, we study the path planning problem for two robots who want to minimize the worst-case evacuation time on the unit disk, that is, the time till both of them evacuate. The robots are initially placed at the center of the disk. In order to evacuate, they need to reach an unknown point, the exit, on the boundary of the disk. Once one of the robots finds the exit, it will

Given a string T of length n, a substring u=T[i..j] of T is called a shortest unique substring (SUS) for an interval [s,t] if (a) u occurs exactly once in T, (b) u contains the interval [s,t] (i.e. i≤s≤t≤j), and (c) every substring v of T with |v|<|u| containing [s,t] occurs at least twice in T. Given a query interval [s,t]⊂[1,n], the interval SUS problem is to output all the SUSs for the interval

We study the worst-case behavior of Turán-like bounds for unweighted and weighted independent sets in bounded-degree graphs. In particular, we revisit a randomized approach of Boppana that forms a simple 1-round distributed algorithm, as well as a streaming algorithm and a preemptive online algorithm. We show that it gives a tight (Δ+1)/2-approximation in unweighted graphs of maximum degree Δ, which

We study the online Parameterized Dictionary Matching with One Gap problem (PDMOG) which is the following. Preprocess a dictionary D of d patterns, where each pattern contains a special gap symbol that can match any string, so that given a text T arriving online, a character at a time, we can report all the patterns from D that parameterized match to suffixes of the text that has arrived so far, before

We study the positionality of trigger strategies Nash equilibria σ‾ for the N-player SCAR games ΓN(G|s0,γ,ε) (with N≥3). Our study is exhaustive with respect to types of graphs G, initial states s0 and values of N,γ,ε. We conclude that in the majority of cases, profiles σ‾ are nonpositional. Whenever σ‾ are positional a key role is played by paths and the ε, γ values (especially whether ε>0 or not)

Consider a group of people who want to know the “rich list” among them, namely the ranking in terms of their total assets, without revealing any information about the actual value of their assets. This can be achieved by a “secure ranking computation,” which was first considered by Jiang and Gong (CT-RSA 2006); they constructed a secure ranking computation protocol based on a public-key cryptosystem

We consider the parameterized complexity of the problem of tracking shortest s-t paths in graphs, motivated by applications in security and wireless networks. Given an undirected and unweighted graph with a source s and a destination t, Tracking Shortest Paths asks if there exists a k-sized subset of vertices (referred to as tracking set) that intersects each shortest s-t path in a distinct set of

We introduce a new metric of match, called Cartesian tree matching, which means that two strings match if they have the same Cartesian trees. Based on Cartesian tree matching, we define single pattern matching, multiple pattern matching, and indexing problems. We propose a linear time algorithm for single pattern matching, and randomized linear time algorithms for multiple pattern matching and indexing

The maximum independent set problem is known to be NP-hard in the class of subcubic graphs, i.e. graphs of vertex degree at most 3. We study complexity of the problem on hereditary subclasses of subcubic graphs. Each such subclass can be described by means of forbidden induced subgraphs. In case of finitely many forbidden induced subgraphs a necessary condition for polynomial-time solvability of the

Some microfluidic lab-on-chip devices contain modules whose function is to mix two fluids, called reactant and buffer, in desired proportions. In one of the technologies for fluid mixing the process can be represented by a directed acyclic graph whose nodes represent micro-mixers and edges represent micro-channels. A micro-mixer has two input channels and two output channels; it receives two fluid

The S-structure connectivity κ(G;S) and S-substructure connectivity κs(G;S) of graph G with structure graph S, which are newly proposed in recent years, can better measure fault tolerance of networks. In this paper, we study κ(BHn;S) and κs(BHn;S) of n-dimensional balanced hypercube BHn, which is a relatively popular network topology proposed recently, for S∈{Pk,C6α,K1,r} where 4≤k≤n, 6≤6α≤n and 4≤r≤5

A network's fault diagnosability is the maximum number of nodes(or processors) that are allowed to fail, while still being able to be identified by analyzing the sydrome of mutual testing, under the well-known PMC diagnostic model. It is a crucial indicator of the network's reliability. The original definition of diagnosability is often too strict to realistically reflect a network's robustness, because

For a Boolean function f:{0,1}n→{0,1} computed by a Boolean circuit C over a finite basis B, the energy complexity of C (denoted by ECB(C)) is the maximum over all inputs {0,1}n of the number gates of the circuit C (excluding the inputs) that output a one. Energy Complexity of a Boolean function over a finite basis B denoted by ECB(f)=defminC⁡ECB(C) where C is a Boolean circuit over B computing f.

The Closest Substring problem asks whether there exists a consensus string w of given length ℓ such that each string in a set of strings L has a substring whose edit distance is at most r (called the radius) from w. The Closest Substring problem has been studied for finite sets of strings and is known to be NP-hard. We show that the Closest Substring problem for regular languages represented by nondeterministic

This paper is concerned with learners who aim to learn patterns in infinite binary sequences: shown longer and longer initial segments of a binary sequence, they either attempt to predict whether the next bit will be a 0 or will be a 1 or they issue forecast probabilities for these events. Several variants of this problem are considered. In each case, a no-free-lunch result of the following form is

The quest for efficient sorting is ongoing, and we will explore a graph-based stable sorting strategy, in particular employing comparison graphs. We use the topological sort to map the comparison graph to a linear domain, and we can manipulate our graph such that the resulting topological sort is the sorted array. By taking advantage of the many relations between Hamiltonian paths and topological sorts

For a given b∈Nn and a hypergraph H=(V,E) with maximum degree Δ, the b-set multicover problem which we are concerned with in this paper may be stated as follows: find a minimum cardinality subset C⊆E such that no vertex vi∈V is contained in less than bi hyperedges of C. Peleg, Schechtman, and Wool (1997) conjectured that for any fixed Δ and b=mini⁡bi, the problem cannot be approximated with a ratio

Every square matrix A=(auv)∈Cn×n can be represented as a digraph having n vertices. In the digraph, a block (or 2-connected component) is a maximally connected subdigraph that has no cut-vertex. The determinant and the permanent of a matrix can be calculated in terms of the determinant and the permanent of some specific induced subdigraphs of the blocks in the digraph. Interestingly, these induced