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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. GarthGarthFor 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 DOLFIN-dev@xxxxxxxxxx http://www.fenics.org/mailman/listinfo/dolfin-dev
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