Changeset [6c89645a1051aba6d5b528483740576511ffce78] by Jed Brown

Add -dfs_assemble_reduced, uncouples components in matrix assembly.

This is particularly useful to improve AMG performance. ML and BoomerAMG don't have block matrix formats so inter-component coupling significantly adds to the cost. PETSc has block smoothers and a more efficient storage scheme so these extra entries are normally very cheap to leave in, even if the coupling is weak (leaving them in trades metadata for useful data). It would be really nice if the AMG packages could just provide interpolation matrices, respecting the nodal structure, and let PETSc handle the rest. http://github.com/jedbrown/dohp/...