[petsc-users] A question on Schur complement

[saturday luis]

Thanks, Jed.

It seems that MatCreateLRC requires two dense matrices for U and V
according to the page
http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreateLRC.html

Not sure if it is applicable to sparse matrices.

2018-01-26 12:09 GMT-08:00 Jed Brown <jed at jedbrown.org>:

> saturday luis <luis.saturday at gmail.com> writes:
>
> > Hi PETSc team:
> >
> > I want to consult for a good way of doing an approximated Schur
> complement
> > matrix. So I just want to handle a matrix in the format C + B^t B, or
> > sometimes B^t B.
> >
> > An easy way is to run with the MatCreateSchurComplement to create C + B^t
> > inv A B, wherein A is an identity matrix. The downside is that the matrix
> > free style does not allow for algebraic preconditioners.
>
> MatCreateLRC is more natural in this context.
>
> Even if you solve with LSQR, you'll likely need some explicit
> representation for preconditioning.
>
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