Got it! Thanks, Manav
> On Mar 29, 2018, at 4:13 PM, Jed Brown <j...@jedbrown.org> wrote: > > Manav Bhatia <bhatiama...@gmail.com> writes: > >> Thanks, Matt. >> >> I also read page 72 in the manual about creating and assembling matrices. >> >> Just so that I understand correctly, MatGetLocalSubMatrix is a generic call >> to create submatrices in the split-local or split-global space? So, it is >> primarily a matter of the isrow and iscol? > > Yes. > >> The manual says that this provides a “view” matrix, so any updates to this >> submatrix should show up in the global? >> >> How is MatCreateSubMatrixVirtual different? Is this different from a “view” >> matrix? > > That is also a view, but specified in terms of the global space rather > than the local space. It's normally used by solvers and other places > where you need the action of the submatrix while the local submatrix is > generally used for assembly. > >> >>> On Mar 29, 2018, at 3:10 PM, Matthew Knepley <knep...@gmail.com> wrote: >>> >>> On Thu, Mar 29, 2018 at 3:28 PM, Manav Bhatia <bhatiama...@gmail.com >>> <mailto:bhatiama...@gmail.com>> wrote: >>> Hi, >>> >>> I have quick questions about MatCreateSubMatrix: >>> >>> — Once the sub matrix is created, do I need to keep the IS (isrow and >>> iscol) in memory till this matrix is active, or can I destroy it >>> immediately after the creation of the matrix and continue to use the matrix? >>> >>> You can destroy it. >>> >>> — Is the assembly begin/end supposed to be called on the submatrix or the >>> original full matrix? Is it a problem is I call this on both? >>> >>> The SubMatrix is not a view. Its a fully independent matrix. >>> >>> — If I modify values in the sub matrix, would these be reflected in the >>> original matrix after assembly begin/end, or do I need to do something else >>> for that to happen? >>> >>> No. Do you want something like this >>> >>> >>> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetLocalSubMatrix.html >>> >>> <http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetLocalSubMatrix.html> >>> >>> Thanks, >>> >>> Matt >>> >>> Thanks, >>> Manav >>> >>> >>> >>> >>> >>> -- >>> 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 >>> >>> https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>