 matrix. Note that in parallel, each processor owns
a local part of the global hypergraph
(a submatrix of the whole matrix).
The hypergraph data type is <i>struct HGraph</i>, and contains
information like number of vertices, hyperedges, pins, compressed
storage of all pins, optional vertex and edge weights, pointers
to relevant communicators, and more. One cryptic notation needs an
explanation: The arrays <i>hindex, hvertex</i> are used to
look up vertex info given a hyperedge, and <i>vindex, vedge</i> are
