Some of the Petsc routines have been changed for use in ParPre. If you use Petsc as an independent package, you need not be aware of this, since the changes affect internal routines. No calling sequences of user routines were changed. It is necessary to install Petsc before ParPre, since the ParPre installation adds routines to some Petsc libraries.
The Petsc library home page is
http://www.mcs.anl.gov/petsc/petsc.htmland the latest version of the library can be downloaded from there.