6 research outputs found
Fast Algorithms for Constructing Maximum Entropy Summary Trees
Karloff? and Shirley recently proposed summary trees as a new way to
visualize large rooted trees (Eurovis 2013) and gave algorithms for generating
a maximum-entropy k-node summary tree of an input n-node rooted tree. However,
the algorithm generating optimal summary trees was only pseudo-polynomial (and
worked only for integral weights); the authors left open existence of a
olynomial-time algorithm. In addition, the authors provided an additive
approximation algorithm and a greedy heuristic, both working on real weights.
This paper shows how to construct maximum entropy k-node summary trees in time
O(k^2 n + n log n) for real weights (indeed, as small as the time bound for the
greedy heuristic given previously); how to speed up the approximation algorithm
so that it runs in time O(n + (k^4/eps?) log(k/eps?)), and how to speed up the
greedy algorithm so as to run in time O(kn + n log n). Altogether, these
results make summary trees a much more practical tool than before.Comment: 17 pages, 4 figures. Extended version of paper appearing in ICALP
201
The classical origin of modern mathematics
The aim of this paper is to study the historical evolution of mathematical
thinking and its spatial spreading. To do so, we have collected and integrated
data from different online academic datasets. In its final stage, the database
includes a large number (N~200K) of advisor-student relationships, with
affiliations and keywords on their research topic, over several centuries, from
the 14th century until today. We focus on two different topics, the evolving
importance of countries and of the research disciplines over time. Moreover we
study the database at three levels, its global statistics, the mesoscale
networks connecting countries and disciplines, and the genealogical level