[petsc-users] reusing LU factorization?

[David Liu]

yes, I am repeatedly calling KSPSolve. I set the operator once at the
beginning, but I change some of the elements of the operator between solves
without changing the nonzero pattern.


On Tue, Jan 28, 2014 at 2:58 PM, Jed Brown <jed at jedbrown.org> wrote:

> David Liu <daveliu at mit.edu> writes:
>
> > Hi, I'm writing an application that solves a sparse matrix many times
> using
> > Pastix. I notice that the first solves takes a very long time, while the
> > subsequent solves are very fast. I don't fully understand what's going on
> > behind the curtains, but I'm guessing it's because the very first solve
> has
> > to read in the non-zero structure for the LU factorization, while the
> > subsequent solves are faster because the nonzero structure doesn't
> change.
>
> How are you doing this?  Repeated calls to KSPSolve?  Are you changing
> the operator between solves?
>
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