Learning Nearest Neighbor Graphs from Noisy Distance Samples Noisy - PowerPoint PPT Presentation

Learning Nearest Neighbor Graphs from Learning Nearest Neighbor Graphs from Noisy Distance Samples Noisy Distance Samples Blake Mason, Ardhendu Tripathy, & Robert Nowak Blake Mason, Ardhendu Tripathy, & Robert Nowak

Motivation Wish to learn ‘ most similar’ or ‘ closest’ items to a given from noisy measurements

Motivation Wish to learn ‘ most similar’ or ‘ closest’ items to a given from noisy measurements amazon.com/discover

Motivation Wish to learn ‘ most similar’ or ‘ closest’ items to a given from noisy measurements Fujitsu white paper

Motivation Wish to learn ‘ most similar’ or ‘ closest’ items to a given from noisy measurements We don’t know the given a priori. We want to answer ‘closest’ queries for any item quickly!

The Nearest Neighbor Graph Problem Sharma et al. (2015)

Preliminaries and Notation • • •

Outline of ANNTri

Elimination via the triangle inequality j k i l

Triangle Inequality Bounds

Theoretical Results • Worst case complexity is always O(n 2 ) • In general, order matters

Theoretical Results • Often, we can do better:

Theoretical Results • An example of separation:

Theoretical Results

Experimental Results • Simulated data • 100 points in ℝ 2 • 10 clusters of 10 points • Euclidean distance • Gaussian noise, 𝜏 2 = 0.1

Experimental Results • Compare against Random sampling • Test effect of triangle inequality

Experimental Results • The metric is (2d) Euclidean • We can compare against (distance) matrix completion • With a distance matrix, the graph can be computed easily

Experimental Results • What shoes are most similar?

Experimental Results • What shoes are most similar? • 85 images from UTZappos50K dataset

Experimental Results • What shoes are most similar? • 85 images from UTZappos50K dataset • Human judgements collected by Heim et al., (2015).

Experimental Results

Experimental Results • What shoes are most similar? • 85 images from UTZappos50K dataset • Human judgements collected by Heim et al., (2015).

Experimental Results • What shoes are most similar? • 85 images from UTZappos50K dataset • Human judgements collected by Heim et al., (2015).

Main takeways for ANNTri 1. ANNTri finds the nearest neighbor graph for general metrics using the triangle inequality 2. Only requires access to noisy oracle 3. In favorable settings, requires 𝑷(𝒐𝒎𝒑𝒉 𝒐 𝚬 −𝟑 ) queries versus 𝑷 𝒐 𝟑 𝚬 −𝟑 needed by brute force!