how can I know which hyperedge is the vertex separator from the Hmetis ?

thanks

I want to decompose a matrix and hope to know the coupling constraint, which is a hyperedge

RE: I presume since you are

I presume since you are modeling the matrix via a hypergraph, then what you are looking for are the hyperedges that are cut by the partitioning. To find those, given the partitioning computing by hMetis, you need to find which hyperedges contain nodes that were assigned to different partitions. Then those hyperedges will correspond to the separator vertices.