Coarsening according to Aij #10
Description
Strongest neighbors j of cell i means those with the largest magnitude of Aij. RUGE STEUBEN??
See 24.5.3 Algebraic Multigrid from http://jullio.pe.kr/fluent6.1/help/html/ug/node837.htm
alternate restriction matrices (ii)
that fancy thing that they do in the Wesselling book