Well, in my stokes/uzawa codes I get much worst times, more iterations and the global error diverges. (But I've to think a little more about it, even in the first iteration i get different times.) So they don't work anymore. :(
So I tested with convection-difusion and please take a look at the solutions. Even with the LU solver. On Friday 26 September 2008, Garth N. Wells wrote: > Garth N. Wells wrote: > > Nuno David Lopes wrote: > >> Is there a simple way of setting an initial guess for an Iterative > >> LinearSolver? > >> In Umfpack and PETSc the default initial guess is the zero vector right? > > > > At the moment, yes (note the UMFPACK is an LU solver, so an initial > > guess doesn't do anything). > > > > It's very simple, and I've been meaning to add an option for using an > > initial guess. It's also useful for Newton solvers. I'll add something > > in the next few days. > > I've added this, although it's untested. Let me know if it works ok. > > Garth > > > Garth > > > >> For time dependent problems it would be great if one could use the last > >> step solutions as the initial guess. > >> I was thinking of something like > >> ----------------------------------------- > >> solver.solve(A,x_(n+1),x_n,b) > >> ----------------------------------------- > >> where x_n is the initial guess for the iterative solver. > >> > >> Also another doubt, (i'm guessing that is my math ignorance only) > >> is it usual that PETSc::gmres with hypre::amg preconditioner doesn't > >> work. (After reading that it is so powerfull...) > >> In a Stokes 566000^2 subsystem it simply blows up with all of the RAM > >> memory (16Gb). > >> (I tried it with simpler problems but with bigger systems and it > >> worked perfectly, converging in <10 iterations.) > >> > >> Sorry for some disturbance in the troubled-hard-development times you > >> are having and thanks again. > > > > _______________________________________________ > > DOLFIN-dev mailing list > > [email protected] > > http://www.fenics.org/mailman/listinfo/dolfin-dev -- Nuno David Lopes e-mail:[EMAIL PROTECTED] (FCUL/CMAF) [EMAIL PROTECTED] (ISEL) http://ptmat.ptmat.fc.ul.pt/%7Endl/ Fri Sep 26 10:20:36 WEST 2008 _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
