LIPICS - Leibniz International Proceedings in Informatics

http://drops.dagstuhl.de/opus/institut_lipics.php

List of Papers (Total 3,006)

On Fair Division for Indivisible Items

We consider the task of assigning indivisible goods to a set of agents in a fair manner. Our notion of fairness is Nash social welfare, i.e., the goal is to maximize the geometric mean of the utilities of the agents. Each good comes in multiple items or copies, and the utility of an agent diminishes as it receives more items of the same good. The utility of a bundle of items for...

A 5-Approximation for Universal Facility Location

In this paper, we propose and analyze a local search algorithm for the Universal facility location problem. Our algorithm improves the approximation ratio of this problem from 5.83, given by Angel et al., to 5. A second major contribution of the paper is that it gets rid of the expensive multi operation that was a mainstay of all previous local search algorithms for capacitated...

Constant Factor Approximation Algorithm for Uniform Hard Capacitated Knapsack Median Problem

In this paper, we give the first constant factor approximation algorithm for capacitated knapsack median problem (CKnM) for hard uniform capacities, violating the budget by a factor of 1+epsilon and capacities by a 2+epsilon factor. To the best of our knowledge, no constant factor approximation is known for the problem even with capacity/budget/both violations. Even for the...

On the Way to Alternating Weak Automata

Different types of automata over words and trees offer different trade-offs between expressivity, conciseness, and the complexity of decision procedures. Alternating weak automata enjoy simple algorithms for emptiness and membership checks, which makes transformations into automata of this type particularly interesting. For instance, an algorithm for solving two-player infinite...

Hyper Partial Order Logic

We define HyPOL, a local hyper logic for partial order models, expressing properties of sets of runs. These properties depict shapes of causal dependencies in sets of partially ordered executions, with similarity relations defined as isomorphisms of past observations. Unsurprisingly, since comparison of projections are included, satisfiability of this logic is undecidable. We...

Shortest k-Disjoint Paths via Determinants

The well-known k-disjoint path problem (k-DPP) asks for pairwise vertex-disjoint paths between k specified pairs of vertices (s_i, t_i) in a given graph, if they exist. The decision version of the shortest k-DPP asks for the length of the shortest (in terms of total length) such paths. Similarly, the search and counting versions ask for one such and the number of such shortest...

Graph Pattern Polynomials

Given a host graph G and a pattern graph H, the induced subgraph isomorphism problem is to decide whether G contains an induced subgraph that is isomorphic to H. We study the time complexity of induced subgraph isomorphism problems when the pattern graph is fixed. Nesetril and Poljak gave an O(n^{k omega}) time algorithm that decides the induced subgraph isomorphism problem for...

Popular Matchings in Complete Graphs

Our input is a complete graph G = (V,E) on n vertices where each vertex has a strict ranking of all other vertices in G. The goal is to construct a matching in G that is "globally stable" or popular. A matching M is popular if M does not lose a head-to-head election against any matching M': here each vertex casts a vote for the matching in {M,M'} where it gets a better assignment...

A Hypersequent Calculus with Clusters for Tense Logic over Ordinals

Prior's tense logic forms the core of linear temporal logic, with both past- and future-looking modalities. We present a sound and complete proof system for tense logic over ordinals. Technically, this is a hypersequent system, enriched with an ordering, clusters, and annotations. The system is designed with proof search algorithms in mind, and yields an optimal coNP complexity...

Lambda-Definable Order-3 Tree Functions are Well-Quasi-Ordered

Asada and Kobayashi [ICALP 2017] conjectured a higher-order version of Kruskal's tree theorem, and proved a pumping lemma for higher-order languages modulo the conjecture. The conjecture has been proved up to order-2, which implies that Asada and Kobayashi's pumping lemma holds for order-2 tree languages, but remains open for order-3 or higher. In this paper, we prove a variation...

Space Complexity of Two Adaptive Bitprobe Schemes Storing Three Elements

We consider the following set membership problem in the bitprobe model - that of storing subsets of size at most three from a universe of size m, and answering membership queries using two adaptive bitprobes. Baig and Kesh [Mirza Galib Anwarul Husain Baig and Deepanjan Kesh, 2018] proposed a scheme for the problem which takes O(m^{2/3}) space. In this paper, we present a proof...

Towards a General Direct Product Testing Theorem

The Direct Product encoding of a string a in {0,1}^n on an underlying domain V subseteq ([n] choose k), is a function DP_V(a) which gets as input a set S in V and outputs a restricted to S. In the Direct Product Testing Problem, we are given a function F:V -> {0,1}^k, and our goal is to test whether F is close to a direct product encoding, i.e., whether there exists some a in {0...

The Cayley-Graph of the Queue Monoid: Logic and Decidability

We investigate the decidability of logical aspects of graphs that arise as Cayley-graphs of the so-called queue monoids. These monoids model the behavior of the classical (reliable) fifo-queues. We answer a question raised by Huschenbett, Kuske, and Zetzsche and prove the decidability of the first-order theory of these graphs with the help of an - at least for the authors - new...

Verification of Timed Asynchronous Programs

In this paper, we address the verification problem for timed asynchronous programs. We associate to each task, a deadline for its execution. We first show that the control state reachability problem for such class of systems is decidable while the configuration reachability problem is undecidable. Then, we consider the subclass of timed asynchronous programs where tasks are...

Quasipolynomial Hitting Sets for Circuits with Restricted Parse Trees

We study the class of non-commutative Unambiguous circuits or Unique-Parse-Tree (UPT) circuits, and a related model of Few-Parse-Trees (FewPT) circuits (which were recently introduced by Lagarde, Malod and Perifel [Guillaume Lagarde et al., 2016] and Lagarde, Limaye and Srinivasan [Guillaume Lagarde et al., 2017]) and give the following constructions: - An explicit hitting set of...

On the Probabilistic Degree of OR over the Reals

We study the probabilistic degree over R of the OR function on n variables. For epsilon in (0,1/3), the epsilon-error probabilistic degree of any Boolean function f:{0,1}^n -> {0,1} over R is the smallest non-negative integer d such that the following holds: there exists a distribution of polynomials Pol in R[x_1,...,x_n] entirely supported on polynomials of degree at most d such...

Continuous Algorithms (Invited Paper)

While the design of algorithms is traditionally a discrete endeavour, in recent years many advances have come from continuous perspectives. Typically, a continuous process, deterministic or randomized, is designed and shown to have desirable properties, such as approaching an optimal solution or a target distribution, and an algorithm is derived from this by appropriate...

Algorithms for the Asymmetric Traveling Salesman Problem (Invited Paper)

The traveling salesman problem is one of the most fundamental optimization problems. Given n cities and pairwise distances, it is the problem of finding a tour of minimum total distance that visits each city once. In spite of significant research efforts, current techniques seem insufficient for settling the approximability of the traveling salesman problem. The gap in our...

Model Checking Randomized Security Protocols (Invited Paper)

The design of security protocols is extremely subtle and is prone to serious faults. Many tools for automatic analysis of such protocols have been developed. However, none of them have the ability to model protocols that use explicit randomization. Such randomized protocols are being increasingly used in systems to provide privacy and anonymity guarantees. In this talk we...

Random Testing for Distributed Systems with Theoretical Guarantees (Invited Paper)

Random testing has proven to be an effective way to catch bugs in concurrent and distributed systems. This is surprising, as the space of executions is enormous and conventional formal methods intuition would suggest that bad behaviors would only be found by extremely unlikely coincidences. Empirically, many bugs in distributed systems can be explained by interactions among only...

The Completeness of BCD for an Operational Semantics

We give a completeness theorem for the BCD theory of intersection types in an operational semantics based on logical relations.

A Formal Study of Boolean Games with Random Formulas as Payoff Functions

In this paper, we present a probabilistic analysis of Boolean games. We consider the class of Boolean games where payoff functions are given by random Boolean formulas. This permits to study certain properties of this class in its totality, such as the probability of existence of a winning strategy, including its asymptotic behaviour. With the help of the Coq proof assistant, we...

Covering Spaces in Homotopy Type Theory

Broadly speaking, algebraic topology consists of associating algebraic structures to topological spaces that give information about their structure. An elementary, but fundamental, example is provided by the theory of covering spaces, which associate groups to covering spaces in such a way that the universal cover corresponds to the fundamental group of the space. One natural...

Permutability in Proof Terms for Intuitionistic Sequent Calculus with Cuts

This paper gives a comprehensive and coherent view on permutability in the intuitionistic sequent calculus with cuts. Specifically we show that, once permutability is packaged into appropriate global reduction procedures, it organizes the internal structure of the system and determines fragments with computational interest, both for the computation-as-proof-normalization and the...

A Shallow Embedding of Pure Type Systems into First-Order Logic

We define a shallow embedding of logical proof-irrelevant Pure Type Systems (piPTSs) into minimal first-order logic. In logical piPTSs a distinguished sort *^p of propositions is assumed. Given a context Gamma and a Gamma-proposition tau, i.e., a term tau such that Gamma |- tau : *^p, the embedding translates tau and Gamma into a first-order formula F_Gamma(tau) and a set of...