\chapter{{\tt BKL}: Block Kernighan-Lin Object}
\label{chapter:BKL}
\par
Our {\tt BKL} object is used to find an initial separator of a
graph.
Its input is a {\tt BPG} bipartite graph object that represents the
domain-segment graph of a domain decomposition of the graph.
After a call to the {\tt BKL\_fidmat()} method, the object contains
a two-color partition of the graph that is accessible via the
{\tt colors[]} and {\tt cweights[]} vectors of the object.

