dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Tue, Apr 01, 2008 at 11:23:29AM +0200, Martin Sandve Alnæs wrote:
> 2008/4/1, Kent-Andre Mardal <kent-and@xxxxxxxxx>:
> >
> >  tir, 01.04.2008 kl. 11.08 +0200, skrev Martin Sandve Alnæs:
> >
> > > I don't see what's the point of that. The only reasons for
> >  > Matrix/Vector are related to having a single LA backend in each
> >  > application run, but a variety of solvers may be used in the same
> >  > application.
> >  >
> >
> >
> > I thought the reason for having Matrix/Vector was to ensure that only
> >  GenericMatrix/GenericVector functionality was used. I guess the PETSc
> >  and the uBlas families now live seperate lives.
> 
> Then why don't you come up with an example of where this makes sense
> for solvers.

Here's an example:

Choosing the type of solver based on some criterion and then
reusing the solver:

   // At startup
   LinearSolver* solver = 0;
   if (solver_type == "direct")
     solver = new LUSolver();
   else
     solver = new KrylovSolver()

   // Then reuse it
   while (t < T)
   {
     ...
     solver->solve(A, x, b);
   }

This is used in the ODE solvers, where one may specify the type of
solver used to solve the linearized equations in each iteration based
on a parameter.

When calling LUSolver::solve(), it needs to choose a specific backend
for the solution, depending on the backend used for A, x, b. Same for
KrylovSolver.

Still not sure if it should be LinearSolver or GenericLinearSolver
above.

-- 
Anders