29 research outputs found
A Combinatorial, Strongly Polynomial-Time Algorithm for Minimizing Submodular Functions
This paper presents the first combinatorial polynomial-time algorithm for
minimizing submodular set functions, answering an open question posed in 1981
by Grotschel, Lovasz, and Schrijver. The algorithm employs a scaling scheme
that uses a flow in the complete directed graph on the underlying set with each
arc capacity equal to the scaled parameter. The resulting algorithm runs in
time bounded by a polynomial in the size of the underlying set and the largest
length of the function value. The paper also presents a strongly
polynomial-time version that runs in time bounded by a polynomial in the size
of the underlying set independent of the function value.Comment: 17 page
Duality between Feature Selection and Data Clustering
The feature-selection problem is formulated from an information-theoretic
perspective. We show that the problem can be efficiently solved by an extension
of the recently proposed info-clustering paradigm. This reveals the fundamental
duality between feature selection and data clustering,which is a consequence of
the more general duality between the principal partition and the principal
lattice of partitions in combinatorial optimization
Envy-freeness and maximum Nash welfare for mixed divisible and indivisible goods
We study fair allocation of resources consisting of both divisible and
indivisible goods to agents with additive valuations. When only divisible or
indivisible goods exist, it is known that an allocation that achieves the
maximum Nash welfare (MNW) satisfies the classic fairness notions based on
envy. In addition, properties of the MNW allocations for binary valuations are
known. In this paper, we show that when all agents' valuations are binary and
linear for each good, an MNW allocation for mixed goods satisfies the
envy-freeness up to any good for mixed goods. This notion is stronger than an
existing one called envy-freeness for mixed goods (EFM), and our result
generalizes the existing results for the case when only divisible or
indivisible goods exist. Moreover, our result holds for a general fairness
notion based on minimizing a symmetric strictly convex function. For the
general additive valuations, we also provide a formal proof that an MNW
allocation satisfies a weaker notion than EFM
Reflection methods for user-friendly submodular optimization
Recently, it has become evident that submodularity naturally captures widely
occurring concepts in machine learning, signal processing and computer vision.
Consequently, there is need for efficient optimization procedures for
submodular functions, especially for minimization problems. While general
submodular minimization is challenging, we propose a new method that exploits
existing decomposability of submodular functions. In contrast to previous
approaches, our method is neither approximate, nor impractical, nor does it
need any cumbersome parameter tuning. Moreover, it is easy to implement and
parallelize. A key component of our method is a formulation of the discrete
submodular minimization problem as a continuous best approximation problem that
is solved through a sequence of reflections, and its solution can be easily
thresholded to obtain an optimal discrete solution. This method solves both the
continuous and discrete formulations of the problem, and therefore has
applications in learning, inference, and reconstruction. In our experiments, we
illustrate the benefits of our method on two image segmentation tasks.Comment: Neural Information Processing Systems (NIPS), \'Etats-Unis (2013
Forming and Dissolving Partnerships in Cooperative Game Situations
A group of players in a cooperative game are partners (e.g., as in the form of a union or a joint ownership) if the prospects for cooperation are restricted such that cooperation with players outside the partnership requires the accept of all the partners. The formation of such partnerships through binding agreements may change the game implying that players could have incentives to manipulate a game by forming or dissolving partnerships. The present paper seeks to explore the existence of allocation rules that are immune to this type of manipulation. An allocation rule that distributes the worth of the grand coalition among players, is called partnership formation-proof if it ensures that it is never jointly profitable for any group of players to form a partnership and partnership dissolution-proof if no group can ever profit from dissolving a partnership. The paper provides results on the existence of such allocation rules for general classes of games as well as more specific results concerning well known allocation rules.cooperative games; partnerships; partnership formation-proof; partnership dissolution-proof