8 research outputs found
Convex relaxations for large-scale graphically structured nonconvex problems with spherical constraints: An optimal transport approach
In this paper we derive a moment relaxation for large-scale nonsmooth
optimization problems with graphical structure and spherical constraints. In
contrast to classical moment relaxations for global polynomial optimization
that suffer from the curse of dimensionality we exploit the partially separable
structure of the optimization problem to reduce the dimensionality of the
search space. Leveraging optimal transport and Kantorovich--Rubinstein duality
we decouple the problem and derive a tractable dual subspace approximation of
the infinite-dimensional problem using spherical harmonics. This allows us to
tackle possibly nonpolynomial optimization problems with spherical constraints
and geodesic coupling terms. We show that the duality gap vanishes in the limit
by proving that a Lipschitz continuous dual multiplier on a unit sphere can be
approximated as closely as desired in terms of a Lipschitz continuous
polynomial. The formulation is applied to sphere-valued imaging problems with
total variation regularization and graph-based simultaneous localization and
mapping (SLAM). In imaging tasks our approach achieves small duality gaps for a
moderate degree. In graph-based SLAM our approach often finds solutions which
after refinement with a local method are near the ground truth solution
Proceedings of the Seventh Italian Conference on Computational Linguistics CLiC-it 2020
On behalf of the Program Committee, a very warm welcome to the Seventh Italian Conference on Computational Linguistics (CLiC-it 2020). This edition of the conference is held in Bologna and organised by the University of Bologna. The CLiC-it conference series is an initiative of the Italian Association for Computational Linguistics (AILC) which, after six years of activity, has clearly established itself as the premier national forum for research and development in the fields of Computational Linguistics and Natural Language Processing, where leading researchers and practitioners from academia and industry meet to share their research results, experiences, and challenges