PVM (Parallel Virtual Machine) allows developers to write applications that can run across multiple heterogeneous computers connected over a network as if they were a single parallel computer. PVM has two main components - a library of routines and a daemon that runs on each host. A PVM application consists of multiple sequential programs or tasks that correspond to processes and can be organized in different structures like a star graph with one supervisor task and multiple worker tasks. Common structures include the supervisor-workers model with one supervisor activating worker tasks, and the hierarchy structure which allows workers to create new levels of sub-workers.

1. Parallel Virtual
Machine(pvm)
By:
A. S. AKSHAYA
II MSC(CS)

2. Parallel programming in the parallel virtual
machine(pvm)
 Parallel virtual machine(pvm) was originally developed at oak ridge national
laboratory and the University of tennessee.
 Possible to develop applications on a set of heterogeneous computer connected
by a network logically to the user as a single parallel computer.
 Interoperability among different heterogeneous computer is a major advantage in
pvm.
 A pvm applications is made from a number of task that cooperate to jointly
provide a solution to a single problem.

3. Pvm Environment And Application
Structure
 The computer nodes in the network are called hosts, which could be uniprocessor,
multiprocessor systems, or clusters running in pvm software.
 Pvm has two components:
1. A library of pvm routines,
2. A Daemon that should reside on all the hosts in the virtual machine.
 Pvm console allows the user to interactively start and then alter the virtual machine
at any time during system operation.
 Pvm application is composed of a number of sequential programs, each of which
will correspond to one or more processes in a parallel program.
 One of these sequential programs, which is called the initiating task, has to be
started manually on one of the hosts.

4.  This model of parallel programming is SPMD, which stands for single program
multiple data.
 A pipeline of parallel task that perform input, processing, and output is an example
of parallel task that are performing different function.
 One of the most common structure is the star graph in which the middle node in
the star is called the supervisor and the rest of the nodes are workers.
 The star Structure is often referred to as a supervisor – workers or a master – slaves
model. In this model, the supervisor is the initiating task that activates all the
workers.
 The terms supervisor-workers and hierarchy to refer to the star and the tree
structure.

5. Supervisor-Workers Structure
 Only one level of hierarchy in this structure : one supervisor and many workers.
 The workers, which are also called slaves, are activates the supervisor to perform
calculations.
 The workers may or may not be independent. If they are not independent.

7. Hierarchy Structure
 The hierarchy Structure allows the workers to create new levels of workers.
 The top-level supervisor is the initiating task, which creates a set of workers at the
second level.
 The leaves of the tree are the workers at the lowest level. This structure matches
very well with the organizational of divide and conquer applications.
 Dashed edges in the tree signify a parent – child relationship between the task.