get several submatrices from several matrices and combine submatrices into another matrix

Yujie recrusader at
Wed Dec 31 10:21:17 CST 2008

Hi, PETSc Developers

In parallel mode, I have 3 MPIDense matrices, A1, A2, A3. Now, I need to
exact submatrices B1, B2, B3 in parallel mode from A1, A2, A3 respectively.
I know I should use MatGetSubMatrix(). My problem is in

MatGetSubMatrix(Mat mat,IS isrow,IS iscol,PetscInt csize,MatReuse
cll,Mat *newmat)

, the parameter "isrow" means "rows this processor should obtain". if Bi in
some nodes (cpus) of the cluster (Ai have rows in them) don't have rows, is
it work?

After getting Bi, I will create MPIDense-based C and combine them into C

C= B2
MatSetValues() should work, right?

Could you give me some comments about these operations? thanks a lot. Happy
new year!

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