Locally Compressed Suffix Arrays
We introduce a compression technique for suffix arrays. It is sensitive to the compressibility of the text and local, meaning that random portions of the suffix array can be decompressed by accessing mostly contiguous memory areas. This makes ...
Randomized Rounding in the Presence of a Cardinality Constraint
We consider the problem of generating randomized roundings that satisfy a single cardinality constraint and admit Chernoff-type large deviation bounds for weighted sums of the variables. That this can be done efficiently was proven by Srinivasan [2001], ...
Efficient Matching for Column Intersection Graphs
To improve the quality and efficiency of hypergraph-based matrix partitioners, we investigate high-quality matchings in column intersection graphs of large sparse binary matrices. We show that such algorithms have a natural decomposition in an integer-...
Satisfiability by Maxwell-Boltzmann and Bose-Einstein Statistical Distributions
Recent studies in theoretical computer science have exploited new algorithms and methodologies based on statistical physics for investigating the structure and the properties of the Satisfiability (SAT) problem. We propose a characterization of the SAT ...
An Experimental Study on Approximating k Shortest Simple Paths
We have conducted an extensive experimental study on approximation algorithms for computing k shortest simple paths in weighted directed graphs. Very recently, Bernstein [2010] presented an algorithm that computes a 1 + ε approximated k shortest simple ...
An Audit Tool for Genome Rearrangement Algorithms
We consider the combinatorial problem of sorting a permutation using a minimum number of rearrangement events, which finds application in the estimation of evolutionary distance between species. Many variants of this problem, which we generically refer ...
On a Model of Virtual Address Translation
Modern computers are not Random Access Machines (RAMs). They have a memory hierarchy, multiple cores, and a virtual memory. We address the computational cost of the address translation in the virtual memory. The starting point for our work on virtual ...
Advanced Coarsening Schemes for Graph Partitioning
The graph partitioning problem is widely used and studied in many practical and theoretical applications. Today, multilevel strategies represent one of the most effective and efficient generic frameworks for solving this problem on large-scale graphs. ...
General Document Retrieval in Compact Space
Given a collection of documents and a query pattern, document retrieval is the problem of obtaining documents that are relevant to the query. The collection is available beforehand so that a data structure, called an index, can be built on it to speed ...
Engineering Efficient Paging Algorithms
In the field of online algorithms, paging is a well-studied problem. LRU is a simple paging algorithm that incurs few cache misses and supports efficient implementations. Algorithms outperforming LRU in terms of cache misses exist but are in general ...
Efficient Computation of Shortest Paths in Time-Dependent Multi-Modal Networks
We consider shortest paths on time-dependent multimodal transportation networks in which restrictions or preferences on the use of certain modes of transportation may arise. We model restrictions and preferences by means of regular languages. Methods ...
Paired and Altruistic Kidney Donation in the UK: Algorithms and Experimentation
We study the computational problem of identifying optimal sets of kidney exchanges in the UK. We show how to expand an integer programming-based formulation due to Roth et al. [2007] in order to model the criteria that constitute the UK definition of ...
Candidate Sets for Alternative Routes in Road Networks
We study the computation of good alternatives to the shortest path in road networks. Our approach is based on single via-node routing on top of contraction hierarchies and achieves superior quality and efficiency compared to previous methods. We present ...
User-Constrained Multimodal Route Planning
In the multimodal route planning problem, we are given multiple transportation networks (e.g., pedestrian, road, public transit) and ask for a best integrated journey between two points. The main challenge is that a seemingly optimal journey may have ...
Experiments on Density-Constrained Graph Clustering
Clustering a graph means identifying internally dense subgraphs that are only sparsely interconnected. Formalizations of this notion lead to measures that quantify the quality of a clustering and to algorithms that actually find clusterings. Since, most ...
Fast Compressed Tries through Path Decompositions
Tries are popular data structures for storing a set of strings, where common prefixes are represented by common root-to-node paths. More than 50 years of usage have produced many variants and implementations to overcome some of their limitations. We ...
