On 30 July 2015 at 12:54, Jan Blechta <[email protected]> wrote:
> On Thu, 30 Jul 2015 12:27:47 +0100 > "Garth N. Wells" <[email protected]> wrote: > > > On 30 July 2015 at 12:18, Mikael Mortensen > > <[email protected]> wrote: > > > > > Hi > > > > > > Back from vacation and very pleased :-) to find that I can update my > > > Fenics installation to version 1.6 in less than 10 minutes! Used to > > > take at least a few days. > > > > > > Now I’m trying to upgrade my applications to 1.6 and I just found > > > that some of the common preconditioners (jacobi, bjacobi, > > > additive_schwarz) have gone missing. Any reason for this or is it a > > > mistake? They seem to have disappeared recently from the map > > > _methods_descr in PETScPreconditioner.cpp. > > > > > > > > The code in question was a mess and the wrapping approach > > unsustainable, which is why it was removed. > > The demand for the wrapping comes from the requirement of having > certain amount of control portable across backends. Is this requirement > getting abandoned, or at least weakened? > > It needs to be weakened. A particular reason is that, beyond the most trivial operations, no two backends are the same. For example, with the supported Krylov solvers it's not even possible to set the convergence tolerance and get consistent behaviour across the backends. We also need to interact with backends in the way they were designed to be used, otherwise we end up with complicated, fragile code that can only exploit a very limited subset of the functionality offered by a backend, e.g. PETSc. Some new demos will arrive very soon that include block preconditioning, domain decomposition and curl-curl multigrid, and these require interacting with PETSc the way it was designed to be used. Garth Jan > > > > > You can control the PETSc preconditioners via PETSc options. This > > gives you far greater control, makes DOLFIN code simpler and provides > > greater consistency when using PETSc solver. There will be more > > changes in DOLFIN 1.7 to give greater control over preconditioning. > > > > Garth > > > > > > > > > > > Best regards > > > > > > Mikael > > > > > > _______________________________________________ > > > fenics mailing list > > > [email protected] > > > http://fenicsproject.org/mailman/listinfo/fenics > > > > >
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