[petsc-users] reusing LU factorization?

[David Liu]

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)?
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