316 research outputs found
FPT-Algorithms for Computing Gromov-Hausdorff and Interleaving Distances Between Trees
The Gromov-Hausdorff distance is a natural way to measure the distortion between two metric spaces. However, there has been only limited algorithmic development to compute or approximate this distance. We focus on computing the Gromov-Hausdorff distance between two metric trees. Roughly speaking, a metric tree is a metric space that can be realized by the shortest path metric on a tree. Any finite tree with positive edge weight can be viewed as a metric tree where the weight is treated as edge length and the metric is the induced shortest path metric in the tree. Previously, Agarwal et al. showed that even for trees with unit edge length, it is NP-hard to approximate the Gromov-Hausdorff distance between them within a factor of 3. In this paper, we present a fixed-parameter tractable (FPT) algorithm that can approximate the Gromov-Hausdorff distance between two general metric trees within a multiplicative factor of 14.
Interestingly, the development of our algorithm is made possible by a connection between the Gromov-Hausdorff distance for metric trees and the interleaving distance for the so-called merge trees. The merge trees arise in practice naturally as a simple yet meaningful topological summary (it is a variant of the Reeb graphs and contour trees), and are of independent interest. It turns out that an exact or approximation algorithm for the interleaving distance leads to an approximation algorithm for the Gromov-Hausdorff distance. One of the key contributions of our work is that we re-define the interleaving distance in a way that makes it easier to develop dynamic programming approaches to compute it. We then present a fixed-parameter tractable algorithm to compute the interleaving distance between two merge trees exactly, which ultimately leads to an FPT-algorithm to approximate the Gromov-Hausdorff distance between two metric trees. This exact FPT-algorithm to compute the interleaving distance between merge trees is of interest itself, as it is known that it is NP-hard to approximate it within a factor of 3, and previously the best known algorithm has an approximation factor of O(sqrt{n}) even for trees with unit edge length
Online Embedding of Metrics
We study deterministic online embeddings of metric spaces into normed spaces of various dimensions and into trees. We establish some upper and lower bounds on the distortion of such embedding, and pose some challenging open questions
Computationally Tractable Riemannian Manifolds for Graph Embeddings
Representing graphs as sets of node embeddings in certain curved Riemannian
manifolds has recently gained momentum in machine learning due to their
desirable geometric inductive biases, e.g., hierarchical structures benefit
from hyperbolic geometry. However, going beyond embedding spaces of constant
sectional curvature, while potentially more representationally powerful, proves
to be challenging as one can easily lose the appeal of computationally
tractable tools such as geodesic distances or Riemannian gradients. Here, we
explore computationally efficient matrix manifolds, showcasing how to learn and
optimize graph embeddings in these Riemannian spaces. Empirically, we
demonstrate consistent improvements over Euclidean geometry while often
outperforming hyperbolic and elliptical embeddings based on various metrics
that capture different graph properties. Our results serve as new evidence for
the benefits of non-Euclidean embeddings in machine learning pipelines.Comment: Submitted to the Thirty-fourth Conference on Neural Information
Processing System
Low-Dimensional Hyperbolic Knowledge Graph Embeddings
Knowledge graph (KG) embeddings learn low-dimensional representations of
entities and relations to predict missing facts. KGs often exhibit hierarchical
and logical patterns which must be preserved in the embedding space. For
hierarchical data, hyperbolic embedding methods have shown promise for
high-fidelity and parsimonious representations. However, existing hyperbolic
embedding methods do not account for the rich logical patterns in KGs. In this
work, we introduce a class of hyperbolic KG embedding models that
simultaneously capture hierarchical and logical patterns. Our approach combines
hyperbolic reflections and rotations with attention to model complex relational
patterns. Experimental results on standard KG benchmarks show that our method
improves over previous Euclidean- and hyperbolic-based efforts by up to 6.1% in
mean reciprocal rank (MRR) in low dimensions. Furthermore, we observe that
different geometric transformations capture different types of relations while
attention-based transformations generalize to multiple relations. In high
dimensions, our approach yields new state-of-the-art MRRs of 49.6% on WN18RR
and 57.7% on YAGO3-10
Hyperbolic Deep Neural Networks: A Survey
Recently, there has been a rising surge of momentum for deep representation
learning in hyperbolic spaces due to theirhigh capacity of modeling data like
knowledge graphs or synonym hierarchies, possessing hierarchical structure. We
refer to the model as hyperbolic deep neural network in this paper. Such a
hyperbolic neural architecture potentially leads to drastically compact model
withmuch more physical interpretability than its counterpart in Euclidean
space. To stimulate future research, this paper presents acoherent and
comprehensive review of the literature around the neural components in the
construction of hyperbolic deep neuralnetworks, as well as the generalization
of the leading deep approaches to the Hyperbolic space. It also presents
current applicationsaround various machine learning tasks on several publicly
available datasets, together with insightful observations and identifying
openquestions and promising future directions
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