Parallel Virtual Machine - PVM PVM is both a message passing library and a simple framework for running parallel jobs. Cray provides a standard version of PVM, and a tuned shared-memory version with more limited functionality. This version of PVM communicates between processes using shared memory segments, making it very fast. No PVM daemon is used. Obviously, this versions can only be used for programs in which all processes on on the same machine.
Special action has to be taken for global and static data.
Refer to the discussion in Data Allocation. The need for global or private file units needs to be addresses. No calls to PVM routines which spawn or manipulate tasks are allowed. This call should be placed before any other PVM calls. The integer variable npes should be set to the number of processes needed, or to zero, in which case the environment variable NPES is queried to determine the number of processes.