[petsc-users] AOCreateBasic & AOCreateBasicIS

[Jed Brown]

Hui Zhang <mike.hui.zhang at hotmail.com> writes:

> Maybe my question was unclear.  From the manual
>
> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/AO/AOCreateBasicIS.html#AOCreateBasicIS
>
> AOCreateBasicIS(IS isapp,IS ispetsc,AO *aoout)
>
> is collective on IS so the parallel IS's must already conceptually
> contain all the indices from all the processors in the 'comm' of IS.
> Is this also what you meant?

No, "collective" means that all processes in the communicator must call
the function together.  Usually (not always, documentation should
explain), PETSc makes collective interfaces memory scalable so that each
process provides only its local part.