Search Results for author: Sebastiano Vigna

Found 8 papers, 5 papers with code

Monotonicity in Undirected Networks

1 code implementation13 Jul 2022 Paolo Boldi, Flavio Furia, Sebastiano Vigna

In this paper, we study the problem of score and rank monotonicity for classical centrality measures in the case of undirected networks: in this case, we require that score, or relative importance, improve at both endpoints of the new edge.

Spectral Rank Monotonicity on Undirected Networks

no code implementations2 Feb 2022 Paolo Boldi, Flavio Furia, Sebastiano Vigna

We show that, surprisingly, the situation is very different for undirected graphs, and in particular that PageRank is neither score nor rank monotone.


Scrambled Linear Pseudorandom Number Generators

2 code implementations3 May 2018 David Blackman, Sebastiano Vigna

Then, we describe some scramblers, that is, nonlinear functions applied to the state array that reduce or delete the linear artifacts, and propose combinations of linear transformations and scramblers that give extremely fast pseudorandom number generators of high quality.

Data Structures and Algorithms Cryptography and Security Mathematical Software

Cache-Oblivious Peeling of Random Hypergraphs

1 code implementation2 Dec 2013 Djamal Belazzougui, Paolo Boldi, Giuseppe Ottaviano, Rossano Venturini, Sebastiano Vigna

The computation of a peeling order in a randomly generated hypergraph is the most time-consuming step in a number of constructions, such as perfect hashing schemes, random $r$-SAT solvers, error-correcting codes, and approximate set encodings.

Data Structures and Algorithms

Quasi-Succinct Indices

1 code implementation19 Jun 2012 Sebastiano Vigna

Compressed inverted indices in use today are based on the idea of gap compression: documents pointers are stored in increasing order, and the gaps between successive document pointers are stored using suitable codes which represent smaller gaps using less bits.

Four Degrees of Separation

no code implementations19 Nov 2011 Lars Backstrom, Paolo Boldi, Marco Rosa, Johan Ugander, Sebastiano Vigna

It is not completely clear whether the selected individual is part of the five, so this could actually allude to distance five or six in the language of graph theory, but the "six degrees of separation" phrase stuck after John Guare's 1990 eponymous play.

Social and Information Networks Physics and Society

HyperANF: Approximating the Neighbourhood Function of Very Large Graphs on a Budget

no code implementations25 Nov 2010 Paolo Boldi, Marco Rosa, Sebastiano Vigna

Recently, the ANF algorithm (approximate neighbourhood function) has been proposed with the purpose of approximating NG(t) on large graphs.

Data Structures and Algorithms Social and Information Networks Physics and Society

Spectral Ranking

1 code implementation1 Dec 2009 Sebastiano Vigna

We sketch the history of spectral ranking, a general umbrella name for techniques that apply the theory of linear maps (in particular, eigenvalues and eigenvectors) to matrices that do not represent geometric transformations, but rather some kind of relationship between entities.

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