[petsc-users] AOApplicationToPetscIS

[Hui Zhang]

I'm implementing a domain decomposition preconditioner.  The dof is ordered by myapp and using AO (and LocalToGlobalMapping for assembly) to map to petsc ordering.
The task I'm doing is building VecScatter's from subdomains to the global domain.  So my program is 

Step 1.  I can map subdomain petsc ordering to subdomain natural ordering.

Step 2.  I can also map subdomain natural ordering to global domain natural ordering.

Step 3.  I have an AO for mapping global domain natural ordering to petsc ordering.

Since each subdomain is defined on a sub-communicator of the communicator of the global domain.  My question is for 

AOApplicationToPetscIS(AO ao,IS is)

can ao and is have different communicators?  Will my program be bad for large problems?  How would you do it?