6,630 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
Grafalgo - A Library of Graph Algorithms and Supporting Data Structures (revised)
This report provides an (updated) overview of {\sl Grafalgo}, an open-source
library of graph algorithms and the data structures used to implement them. The
programs in this library were originally written to support a graduate class in
advanced data structures and algorithms at Washington University. Because the
code's primary purpose was pedagogical, it was written to be as straightforward
as possible, while still being highly efficient. Grafalgo is implemented in C++
and incorporates some features of C++11.
The library is available on an open-source basis and may be downloaded from
https://code.google.com/p/grafalgo/. Source code documentation is at
www.arl.wustl.edu/\textasciitilde jst/doc/grafalgo. While not designed as
production code, the library is suitable for use in larger systems, so long as
its limitations are understood. The readability of the code also makes it
relatively straightforward to extend it for other purposes
Parameterized Approximation Schemes using Graph Widths
Combining the techniques of approximation algorithms and parameterized
complexity has long been considered a promising research area, but relatively
few results are currently known. In this paper we study the parameterized
approximability of a number of problems which are known to be hard to solve
exactly when parameterized by treewidth or clique-width. Our main contribution
is to present a natural randomized rounding technique that extends well-known
ideas and can be used for both of these widths. Applying this very generic
technique we obtain approximation schemes for a number of problems, evading
both polynomial-time inapproximability and parameterized intractability bounds
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