[petsc-users] Question about MatCreateSubMatrix

[Manav Bhatia]

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? 

— 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? 

— 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? 

Thanks,
Manav