PetscSF Object: sf 3 MPI processes
  type: basic
  [0] Number of roots=103, leaves=0, remote ranks=0
  [1] Number of roots=201, leaves=1, remote ranks=1
  [1] 200 <- (2,300)
  [2] Number of roots=301, leaves=0, remote ranks=0
  MultiSF sort=rank-order