2: #include <../src/mat/impls/aij/mpi/mpiaij.h> 4: PetscErrorCode MatGetDiagonalBlock_MPIAIJ(Mat A, Mat *a) 5: { 6: PetscFunctionBegin; 7: *a = ((Mat_MPIAIJ *)A->data)->A; 8: PetscFunctionReturn(PETSC_SUCCESS); 9: }