[petsc-users] reusing LU factorization?

[Jed Brown]

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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