Showing papers by "Alejandro López-Ortiz published in 2004"
Journal Article•
TL;DR: In this article, the authors study the global cardinality constraint (gcc) and propose an O(n 1.5 d) algorithm for domain consistency and O(cn 2 d + n 2.66 )-time algorithm for range consistency.
Abstract: We study the global cardinality constraint (gcc) and propose an O(n 1.5 d) algorithm for domain consistency and an O(cn + dn) algorithm for range consistency where n is the number of variables, d the number of values in the domain, and c an output dependent variable smaller than or equal to n. We show how to prune the cardinality variables in O(n 2 d + n 2.66 ) steps, detect if g cc is universal in constant time and prove that it is NP-Hard to maintain domain consistency on extended-GCC.
65 citations
27 Sep 2004
TL;DR: It is proved that it is NP-Hard to maintain domain consistency on extended-GCC and how to prune the cardinality variables in O(n2d + n2.66) steps is shown.
Abstract: We study the global cardinality constraint (gcc) and propose an O(n1.5d) algorithm for domain consistency and an O(cn + dn) algorithm for range consistency where n is the number of variables, d the number of values in the domain, and c an output dependent variable smaller than or equal to n. We show how to prune the cardinality variables in O(n2d + n2.66) steps, detect if gcc is universal in constant time and prove that it is NP-Hard to maintain domain consistency on extended-GCC.
65 citations
TL;DR: This paper investigates parallel searches on m concurrent rays for a point target t located at some unknown distance along one of the rays and provides a strategy with competitive ratio of 1 + 2(m/p - 1)(m/(m - p) m/p and proves that this is optimal.
42 citations
TL;DR: An output-sensitive data structure is proposed that solves the problem of finding the longest increasing subsequence in a sliding window over a given sequence in time O(n log log n+OUTPUT) for a sequence of n elements.
39 citations
21 Jun 2004
TL;DR: This paper presents an algorithm for identifying frequently occurring items within a sliding window of the last N items seen over an infinite data stream, given the following constraints: the relative frequencies of the item types can vary over the lifetime of the stream.
Abstract: In this paper, we present an algorithm for identifying frequently occurring items within a sliding window of the last N items seen over an infinite data stream, given the following constraints: (1) the relative frequencies of the item types can vary over the lifetime of the stream, provided that they vary sufficiently slowly that for any sliding window of N tuples, with high probability the window could have been generated by a multinomial distribution. We refer to this as the drifting distribution model in the full version of this paper (Golab et al., 2004). (2) The entire sliding window does not fit in the available memory (otherwise, we could simply count all the distinct item types and return those whose frequencies exceed some threshold). (3) The stream may arrive at a high rate, so only a constant number of operations (amortized) is allowed for the processing of each item.
20 citations
TL;DR: This work designs efficient competitive algorithms for discovering hidden information using few queries for both the verification scenario (given an independent set, is it X?) and the discovery scenario (find X without any information).
10 citations
22 Aug 2004
TL;DR: Algorithms to find all projections of a convex polyhedron such that a given set of edges, faces and/or vertices appear on the silhouette are given.
Abstract: The silhouette of polyhedra is an important primitive in application areas such as machine vision and computer graphics. In this paper, we study how to select view points of convex polyhedra such that the silhouette satisfies certain properties. Specifically, we give algorithms to find all projections of a convex polyhedron such that a given set of edges, faces and/or vertices appear on the silhouette.
2 citations
Journal Article•
TL;DR: In this paper, the authors presented an algorithm to find all projections of a convex polyhedron such that a given set of edges, faces and/or vertices appear on the silhouette.
Abstract: The silhouette of polyhedra is an important primitive in application areas such as machine vision and computer graphics. In this paper, we study how to select view points of convex polyhedra such that the silhouette satisfies certain properties. Specifically, we give algorithms to find all projections of a convex polyhedron such that a given set of edges, faces and/or vertices appear on the silhouette. We present an algorithm to solve this problem in O(k 2 ) time for k edges. For orthogonal projections, we give an improved algorithm that is fully adaptive in the number l of connected components formed by the edges, and has a time complexity of O(k log k + kl). We then generalize this algorithm to edges and/or faces appearing on the silhouette.
2 citations
05 Aug 2004
TL;DR: In this paper, the main components of web information retrieval, with emphasis on the algorithmic aspects of web search engine research, are described, and a survey of the main aspects of Web information retrieval is presented.
Abstract: This survey describes the main components of web information retrieval, with emphasis on the algorithmic aspects of web search engine research.
1 citations
05 Aug 2004
TL;DR: A short overview of selected topics in the field of Algorithmic Foundations of the Internet can be found in this article, which is a new area within theoretical computer science and is related to our work.
Abstract: In this paper we present a short overview of selected topics in the field of Algorithmic Foundations of the Internet, which is a new area within theoretical computer science
05 Aug 2004
TL;DR: During the last 25 years the Internet has grown from being a small academic network connecting a few computer science departments to its present size, connecting more than 285 million computers and serving over 800 million users worldwide.
Abstract: During the last 25 years the Internet has grown from being a small academic network connecting a few computer science departments to its present size, connecting more than 285 million computers and serving over 800 million users worldwide [7].