7 research outputs found
Online Maximum Independent Set of Hyperrectangles
The maximum independent set problem is a classical NP-hard problem in
theoretical computer science. In this work, we study a special case where the
family of graphs considered is restricted to intersection graphs of sets of
axis-aligned hyperrectangles and the input is provided in an online fashion. We
prove bounds on the competitive ratio of an optimal online algorithm under the
adaptive offline, adaptive online, and oblivious adversary models, for several
classes of hyperrectangles and restrictions on the order of the input.
We are the first to present results on this problem under the oblivious
adversary model. We prove bounds on the competitive ratio for unit hypercubes,
-bounded hypercubes, unit-volume hypercubes, arbitrary hypercubes, and
arbitrary hyperrectangles, in both arbitrary and non-dominated order. We are
also the first to present results under the adaptive offline and adaptive
online adversary models with input in non-dominated order, proving bounds on
the competitive ratio for the same classes of hyperrectangles; for input in
arbitrary order, we present the first results on -bounded hypercubes,
unit-volume hyperrectangles, arbitrary hypercubes, and arbitrary
hyperrectangles. For input in dominating order, we show that the performance of
the naive greedy algorithm matches the performance of an optimal offline
algorithm in all cases. We also give lower bounds on the competitive ratio of a
probabilistic greedy algorithm under the oblivious adversary model. We conclude
by discussing several promising directions for future work.Comment: 27 pages, 12 figure
Maximizing Neutrality in News Ordering
The detection of fake news has received increasing attention over the past
few years, but there are more subtle ways of deceiving one's audience. In
addition to the content of news stories, their presentation can also be made
misleading or biased. In this work, we study the impact of the ordering of news
stories on audience perception. We introduce the problems of detecting
cherry-picked news orderings and maximizing neutrality in news orderings. We
prove hardness results and present several algorithms for approximately solving
these problems. Furthermore, we provide extensive experimental results and
present evidence of potential cherry-picking in the real world.Comment: 14 pages, 13 figures, accepted to KDD '2
Efficient Algorithms for Constructing an Interpolative Decomposition
Low-rank approximations are essential in modern data science. The
interpolative decomposition provides one such approximation. Its distinguishing
feature is that it reuses columns from the original matrix. This enables it to
preserve matrix properties such as sparsity and non-negativity. It also helps
save space in memory. In this work, we introduce two optimized algorithms to
construct an interpolative decomposition along with numerical evidence that
they outperform the current state of the art.Comment: Disclaimer: we do not have any experiments on very large matrices, so
these findings are only conclusive for relatively small matrice