The two canonical simulation paradigms in PGENESIS are

  1. parallel - all nodes are synchronized by PGENESIS automatically and
  2. farm - no nodes are synchronized by PGENESIS.
The former is useful for network simulations in which different parts of the model running on different nodes must simulate in lockstep, or close to lockstep. The latter is useful for parameter searching applications in which the synchronization is explicitly performed by scripts running on the nodes (e.g., all nodes execute a barrier).

A third, hybrid, paradigm is embodied in the concept of zones. Within a zone, nodes run in the parallel mode, with PGENESIS performing automatic synchronization. The collection of zones runs in farm mode - synchronization is controlled from the scripts. This hybrid mode is useful for parameter searching on large models in which each instance of the model can be parallelized across a number of nodes. It may also be useful for a model of a system in which individual components, simulated in a zone, need only loose synchronization.

Zones can be thought of as a partition of the parallel platform in which no GENESIS messages can cross zone boundaries. Zones are established by the paron command, and are specified in other commands using the @ construct.