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Paper:

TR26-197 | 20th September 2026 09:23

Testing Bipartite in the Bounded-Degree Graph Model, Revisited (A digest of the paper of Fei and Rubinfeld (2026))

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TR26-197
Authors: Oded Goldreich
Publication: 20th September 2026 09:23
Downloads: 16
Keywords: 


Abstract:

We provide a digest of the paper of Fei and Rubinfeld (arXiv 2026), which provides an alternative analysis of the Bipartite Tester of Goldreich and Ron ({\em Combinatorica}, 1999), which operates in the bounded-degree graph model.
Loosely speaking, on input an $n$-vertex graph $G$, the tester selects few vertices, conducts $\tildeO(n^{1/2})$ random walks of polylogarithmic length from each selected vertex, and rejects if and only if an odd cycle is formed by a pair of walks.

While the analysis of the foregoing tester in the rapid-mixing case is quite appealing, the original analysis of the general case is quite imposing; it involves the introduction and analysis of Markov Chains that capture the behavior of random walks on a sequence of residual subgraphs that are iteratively defined by the analysis.
In contrast, Fei and Rubinfeld avoid this iterative process, and present an analysis that only refers to the random walks on the input graph.

More specifically, the original analysis derives a sequence of (non-overlapping) partial 2-partitions of the graph, and stitches them together.
In contrast, the new analysis combines a set of ``fractional'' 2-partitions of the entire graph,
where the combination is obtained by defining adequate vectors that represent these fractional 2-partitions and employing randomized rounding (a la Goemans and Williamson ({\em JACM}, 1995)).

In addition, the new analysis allows for presenting an extremely efficient interactive proof of proximity for Bipartiteness. Such an interactive proof was known before for the rapid-mixing case (Rothblum, Vadhan, and Wigderson ({\em STOC}, 2013)).



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