DOUG overview

DOUG has currently has 2 executables: doug_geom and doug_aggr, which can read different input formats and use different preconditioners:

• the doug_geom executable can read elemental input and use geometric coarse preconditioner,
• the doug_aggr executable can read assembled input, generate mesh locally, use aggregation and aggregation based coarse preconditioners.

They occasionally need to be combined, but it requires more refactoring.