Nuno David Lopes wrote: > 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. >
This should be fixed now. Garth > 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 > > > _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
