On Fri, 15 Mar 2013, Jens Lohne Eftang wrote:
> But when the residual is computed how can I hand it just "b," ? I thought it > would calculate it as A*x-b based on my A and b ...? Nope. As John said, FEMSystem doesn't have any way to tell whether your problem is linear or not. If you've got a linear problem, then it's up to you to tell the nonlinear solver to avoid doing any redundant work, and if you want it to be robust with any solver (or with time integration) then it's up to you to define a solution-dependent residual consistently. Usually this isn't too hard - E.g. if I was solving (grad u, grad v) = (f, v) Then my residual is (f,v)-(grad u, grad v) instead of plain (f,v). If you know you're never going to evaluate your problem from a starting point other than u=0, then you can get away with plain (f,v) as long as you turn off any nonlinear solver option that might call a residual after the first step. But usually people intend to do nonlinear or transient terms eventually too, so it's easier to just start with the linear terms written in a consistent way. --- Roy ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_d2d_mar _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
