Writing an AM layer is a trivial task on most massive parallel machines. All machines supported by PVM include a reliable delivery interconnection network and provide a nonblocking send-and-receive API. This makes for a very simple and fast port of the AM library, mainly consisting of ifdefing the code for reliability. As a bonus, many of the supported architectures come furnished with an optimized AM library. In this case, the task of the AM implementer would simply be to write stubs calling the existing AM API.