Anders Logg wrote: > On Thu, Sep 25, 2008 at 03:11:27PM +0100, Garth N. Wells wrote: >> >> Anders Logg wrote: >>> On Thu, Sep 25, 2008 at 12:41:33PM +0100, 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. >>>> >>>> Garth >>> It would be natural to let the x argument always be the initial >>> guess. I thought we already did this. >>> >>> Would it be enough to make sure that Vector::init() does not reset the >>> values to zero? >>> >> Yes. >> >> The danger is if someone sends an uninitialised vector to the solver. >> >> Garth > > We can just put something like this in the init() functions: > > if (x && size() == N) > return; > > I think we had this a while back but at some point VecZeroEntries was > inserted. >
I think that we should have an option whether or not to use an initial guess. The default can be to use the guess (as in your above code extract). Garth > > > ------------------------------------------------------------------------ > > _______________________________________________ > 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
