Ok thanks, I can see how introducing units to the residual is necessary, but when would it be necessary to introduce units to the state? I would imagine this would only be needed if a numerically differentiated jacobian was being used.
Thanks Colin Quoting Jed Brown <jedbrown at mcs.anl.gov>: > On Tue, Jun 26, 2012 at 2:31 PM, Colin McAuliffe <cjm2176 at > columbia.edu>wrote: > >> Hello, >> >> I would like to use GMRES for a monolithic solution of a multiphysics >> problem. There are drastically different units in the problem and so the >> residual norm is dominated by the terms with the largest units. Is there a >> way to tell petsc to scale the residual before taking the norm to avoid >> this? >> > > You can "fix" it with preconditioning, but then you can only use the > preconditioned residual. You should really fix the units when formulating > the problem. (This does not require formal nondimensionalization, just > introduced units so that state and residuals are of order 1.) > -- Colin McAuliffe PhD Candidate Columbia University Department of Civil Engineering and Engineering Mechanics
