[petsc-users] Solving only for certain rows

[Jed Brown]

Orxan Shibliyev <orxan.shibli at gmail.com> writes:

> I used KSP to solve Ax=b successfully but I would like to solve Ax=b only
> for certain rows. How can I do this?

It's not actually significantly cheaper no matter what you do.  You can
save a little on non-leading constant factors for some methods
(basically permuting the factorization so you only need a partial
back-solve).  This is usually negligible.
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