Mat Object: 1 MPI process
  type: seqaij
row 0: (0, 5.)  (1, 2.)  (3, 3.) 
row 1: (1, 9.)  (2, 7.) 
row 2: (0, 10.)  (2, 12.) 
row 3: (1, 13.)  (3, 15.) 
IS Object: 1 MPI process
  type: stride
Number of indices in (stride) set 2
0 0
1 1
IS Object: 1 MPI process
  type: stride
Number of indices in (stride) set 2
0 2
1 3

Explicit Schur complement of (0,0) in (1,1)
Mat Object: 1 MPI process
  type: seqaij
row 0: (0, 15.1111)  (1, -6.) 
row 1: (0, -10.1111)  (1, 15.) 

Explicit Schur complement of (1,1) in (0,0)
Mat Object: 1 MPI process
  type: seqaij
row 0: (0, 5.)  (1, -0.6) 
row 1: (0, -5.83333)  (1, 9.) 

Preconditioning Schur complement of (0,0) in (1,1)
Mat Object: 1 MPI process
  type: seqaij
row 0: (0, 12.)  (1, -6.) 
row 1: (0, -10.1111)  (1, 15.) 

After update
Mat Object: 1 MPI process
  type: seqaij
row 0: (0, 13.)  (1, -5.) 
row 1: (0, -9.1)  (1, 16.)