OpenAI reports an FPRAS for counting perfect matchings in general graphs

A randomized algorithm approximates the number of perfect matchings in every finite simple undirected graph to relative error ε with failure probability at most δ in worst-case bit time polynomial in the input length, ε⁻¹, and log δ⁻¹; it returns zero with certainty when there is no perfect matching.

Sources for this record

What was already known

A fully polynomial randomized approximation scheme was known for bipartite perfect matchings, while the general-graph counting problem remained open in the manuscript’s account.

AI involvement AI-led

OpenAI credits itself as manuscript author and states that its internal frontier model produced the results in this release. Individual human input is not detailed enough to establish task-only autonomy.

OpenAI is named as author on the manuscript, and its release attributes the results to an internal frontier model. The individual human input is not detailed enough to establish autonomy.

Importance Major

Resolves the long-standing general-graph perfect-matching approximation problem.

Limitations

The algorithm’s guarantee concerns finite simple undirected graphs and randomized relative approximation. OpenAI reports the Lean check; it was not rerun here.

Technical verification Formal (Lean 4)

OpenAI reports a Lean proof matching the selected claim.

Formal checking

The pinned Lean note specifies an FPRAS for every finite simple undirected graph, including zero output on infeasible instances and worst-case polynomial bit time.

Checker
OpenAI-reported Lean 4 / Comparator
Scope
A randomized algorithm approximates the number of perfect matchings in every finite simple undirected graph to relative error ε with failure probability at most δ in worst-case bit time polynomial in the input length, ε⁻¹, and log δ⁻¹; it returns zero with certainty when there is no perfect matching.
Basis
Reported by the linked checker
Evidence source

Checking a formal statement does not establish that it matches the original problem.

Human understanding Few

Few is the default when evidence for a higher level is insufficient. No named person is documented as explaining the central argument for this assessed contribution.

Correction and publication history

2026-10-18 · publication

Primary manuscript, attribution, prior-work, and scoped checking review for non-notifying local inclusion.

Read this published revision