23 research outputs found
Reconciling taxonomy and phylogenetic inference: formalism and algorithms for describing discord and inferring taxonomic roots
Although taxonomy is often used informally to evaluate the results of
phylogenetic inference and find the root of phylogenetic trees, algorithmic
methods to do so are lacking. In this paper we formalize these procedures and
develop algorithms to solve the relevant problems. In particular, we introduce
a new algorithm that solves a "subcoloring" problem for expressing the
difference between the taxonomy and phylogeny at a given rank. This algorithm
improves upon the current best algorithm in terms of asymptotic complexity for
the parameter regime of interest; we also describe a branch-and-bound algorithm
that saves orders of magnitude in computation on real data sets. We also
develop a formalism and an algorithm for rooting phylogenetic trees according
to a taxonomy. All of these algorithms are implemented in freely-available
software.Comment: Version submitted to Algorithms for Molecular Biology. A number of
fixes from previous versio
Ad auctions and cascade model: GSP inefficiency and algorithms
The design of the best economic mechanism for Sponsored Search Auctions
(SSAs) is a central task in computational mechanism design/game theory. Two
open questions concern the adoption of user models more accurate than that one
currently used and the choice between Generalized Second Price auction (GSP)
and Vickrey-Clark-Groves mechanism (VCG). In this paper, we provide some
contributions to answer these questions. We study Price of Anarchy (PoA) and
Price of Stability (PoS) over social welfare and auctioneer's revenue of GSP
w.r.t. the VCG when the users follow the famous cascade model. Furthermore, we
provide exact, randomized, and approximate algorithms, showing that in
real-world settings (Yahoo! Webscope A3 dataset, 10 available slots) optimal
allocations can be found in less than 1s with up to 1000 ads, and can be
approximated in less than 20ms even with more than 1000 ads with an average
accuracy greater than 99%.Comment: AAAI16, to appea
Open Problems in Parameterized and Exact Computation - IWPEC 2006
In September 2006, the Second International Workshop on Parameterized and
Exact Computation was held in Zürich, Switzerland, as part of ALGO 2006. At the
end of IWPEC 2006, a problem session was held. (Most of) the problems mentioned
at this problem session, and some other problems, contributed by the participants of
IWPEC 2006 are listed here
Connection Matrices and the Definability of Graph Parameters
In this paper we extend the Finite Rank Theorem for connection matrices of graph parameters definable in Monadic Second Order Logic with modular counting CMSOL of B. Godlin, T. Kotek and J.A. Makowsky (2008 and 2009), and demonstrate its vast applicability in simplifying known and new non-definability results of graph properties and finding new non-definability results for graph parameters. We also prove a Feferman-Vaught Theorem for the logic CFOL, First Order Logic with the modular counting quantifiers
Connection Matrices and the Definability of Graph Parameters
In this paper we extend and prove in detail the Finite Rank Theorem for
connection matrices of graph parameters definable in Monadic Second Order Logic
with counting (CMSOL) from B. Godlin, T. Kotek and J.A. Makowsky (2008) and
J.A. Makowsky (2009). We demonstrate its vast applicability in simplifying
known and new non-definability results of graph properties and finding new
non-definability results for graph parameters. We also prove a Feferman-Vaught
Theorem for the logic CFOL, First Order Logic with the modular counting
quantifiers