The ParPre library uses MPI for the message passing protocol, and Petsc for intermediate level primitives for distributed matrix manipulation. These packages have to be installed before you can use ParPre.
A program using ParPre preconditioners has to perform some conversion of data structures to Petsc format; see section 3. After the initial setup, the cost of this is essentially zero. See section B for more information on Petsc and the relationship of ParPre to Petsc.