[petsc-users] reusing LU factorization?

Matthew Knepley knepley at gmail.com
Tue Jan 28 13:38:50 CST 2014

On Tue, Jan 28, 2014 at 1:36 PM, David Liu <daveliu at mit.edu> wrote:

> 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.
> My question is, is there any way to save the information obtained from the
> very first solve, so that the next time I run the application, the very
> first solve can be fast too (provided that I still have the same nonzero
> structure)?

No, we do not persist the factored matrices.


What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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