Exact Recovery of Community Structures Using DeepWalk and Node2vec

TL;DR

This paper provides a theoretical analysis of DeepWalk and node2vec, showing they can exactly recover community structures in stochastic blockmodel graphs using matrix factorization techniques, with guarantees improving as the network sparsity increases.

Contribution

The paper offers the first theoretical guarantees for node2vec and DeepWalk's community detection capabilities via matrix factorization analysis, including error bounds and perfect recovery conditions.

Findings

High-probability error bounds for embeddings

Guarantee of perfect community recovery in sparse networks

Validation through numerical experiments and real data

Abstract

Random-walk based network embedding algorithms like DeepWalk and node2vec are widely used to obtain Euclidean representation of the nodes in a network prior to performing downstream inference tasks. However, despite their impressive empirical performance, there is a lack of theoretical results explaining their large-sample behavior. In this paper, we study node2vec and DeepWalk through the perspective of matrix factorization. In particular, we analyze these algorithms in the setting of community detection for stochastic blockmodel graphs (and their degree-corrected variants). By exploiting the row-wise uniform perturbation bound for leading singular vectors, we derive high-probability error bounds between the matrix factorization-based node2vec/DeepWalk embeddings and their true counterparts, uniformly over all node embeddings. Based on strong concentration results, we further show the perfect membership recovery by node2vec/DeepWalk, followed by $K$-means/medians algorithms. Specifically, as the network becomes sparser, our results guarantee that with large enough window size and vertices number, applying $K$-means/medians on the matrix factorization-based node2vec embeddings can, with high probability, correctly recover the memberships of all vertices in a network generated from the stochastic blockmodel (or its degree-corrected variants). The theoretical justifications are mirrored in the numerical experiments and real data applications, for both the original node2vec and its matrix factorization variant.