Variable-dimension Weisfeiler–Leman equivalence on general and subcubic graphs

OpenAI

For joint-update k-dimensional Weisfeiler–Leman equivalence, with k≥2 binary encoded as part of the input and graphs given by explicit adjacency matrices, the test is EXPTIME-complete. The hardness also holds for connected equal-order simple uncolored graphs of maximum degree three.

Sources for this record

What was already known

Each fixed dimension admits polynomial-time tuple refinement. Earlier work showed coNP-hardness when dimension varies and posed the EXPTIME question.

AI involvement AI-led

OpenAI is credited as author of the model-produced reduction and proof. No claim-specific human check or explanation of the construction is documented.

OpenAI is credited as author of the model-produced proof and the repository documents the internal model's central research role.

Importance Notable

The result answers the stated complexity question and extends hardness to subcubic graph pairs.

Limitations

The claim concerns joint-update equivalence under the stated encoding and reductions; graph identification and the published parity-lift construction are different results.

Technical verification Formal (Lean 4)

OpenAI’s formalization catalogue maps the general and connected-subcubic EXPTIME-completeness statements, including binary dimension encoding and adjacency-matrix inputs, to its Lean comparator.

Formal checking

Lean proof of variable-dimension equivalence complexity under the stated graph and input encodings

Checker
OpenAI Lean 4 library and comparator
Scope
Joint-update variable-dimension Weisfeiler–Leman equivalence is EXPTIME-complete on general and connected subcubic graph pairs under the stated input encoding and reductions
Basis
Reported by the linked checker
Evidence source

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

Human understanding Few

The model-produced manuscript explains the reduction, but no human account establishing understanding of its central construction was located; Few is the evidence default, not a report of human incomprehension.

Correction and publication history

2026-10-18 · publication

The result answers the stated complexity question and extends hardness to subcubic graph pairs.

Read this published revision