Central to the operation of a program like PADE is a vehicle for passing messages between nodes, that is, a message-passing library. PADE is based upon the widely used Parallel Virtual Machine (PVM) message-passing library developed at Oak Ridge National Laboratory. Indeed, it is appropriate to regard PADE as a PVM application, in that it utilizes PVM calls for all communication between processors of the virtual machine. Since these calls are of a character that appears to be generic to message-passing libraries, implementation of PADE in alternative message-passing software should be possible by straightforward modification of the source code of PADE (and of the core utility pvmmake, which is described in Chapter 3).
To understand how PADE works, it is probably best to review some of the typical features of a PVM application.