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

Deciding joint-update k-dimensional Weisfeiler–Leman equivalence is $\mathsf{EXPTIME}$-complete when the two graphs are given by explicit adjacency matrices and k ≥ 2 is encoded in binary. The result holds even for connected simple uncolored graphs of equal positive order and maximum degree at most three.