339     Mat B2, T3, T4;  in main()  local
341     PetscCall(MatDuplicate(B, MAT_COPY_VALUES, &B2));  in main()
344     PetscCall(MatAXPY(B2, 1.0, T4, SAME_NONZERO_PATTERN));  in main()
347 …PetscCall(MatDenseGetSubMatrix(B2, PETSC_DECIDE, PETSC_DECIDE, PetscMin(1, K - 1), PetscMin(2, K),…  in main()
357     PetscCall(MatDenseRestoreSubMatrix(B2, &T3));  in main()
359     PetscCall(MatDestroy(&B2));  in main()
362       PetscCall(MatDuplicate(B, MAT_COPY_VALUES, &B2));  in main()
365       PetscCall(MatAXPY(B2, 1.0, T4, SAME_NONZERO_PATTERN));  in main()
368 … PetscCall(MatDenseGetSubMatrix(B2, N - 2, PETSC_DECIDE, PetscMin(1, K - 1), PetscMin(2, K), &T3));  in main()
378       PetscCall(MatDenseRestoreSubMatrix(B2, &T3));  in main()
380       PetscCall(MatDestroy(&B2));  in main()
382       PetscCall(MatDuplicate(B, MAT_COPY_VALUES, &B2));  in main()
385       PetscCall(MatAXPY(B2, 1.0, T4, SAME_NONZERO_PATTERN));  in main()
388       PetscCall(MatDenseGetSubMatrix(B2, PETSC_DECIDE, 2, PetscMin(1, K - 1), PetscMin(2, K), &T3));  in main()
398       PetscCall(MatDenseRestoreSubMatrix(B2, &T3));  in main()
400       PetscCall(MatDestroy(&B2));  in main()