SCOTCH is a software package and libraries for graph, mesh and hypergraph
partitioning, static mapping, and sparse matrix block ordering.

Its purpose of Scotch is to apply graph theory, with a divide and conquer
approach, to scientific computing problems such as graph and mesh partitioning,
static mapping, and sparse matrix ordering, in application domains ranging from
structural mechanics to operating systems or bio-chemistry.

Note: there is an older tarball included in Aster's distfile, but I prefer
a separate distfile from the official site.