  Discrete Event Simulation (DES) is a widely used technique in which the state
of the simulator is updated by events happening at discrete points in time
(hence the name). DES is used to model and analyze many kinds of systems,
including computer architectures, communication networks, street traffic, and
others. Parallel and Distributed Simulation (PADS) aims at improving the
efficiency of DES by partitioning the simulation model across multiple
processing elements, in order to enabling larger and/or more detailed studies
to be carried out. The interest on PADS is increasing since the widespread
availability of multicore processors and affordable high performance computing
clusters. However, designing parallel simulation models requires considerable
expertise, the result being that PADS techniques are not as widespread as they
could be. In this paper we describe ErlangTW, a parallel simulation middleware
based on the Time Warp synchronization protocol. ErlangTW is entirely written
in Erlang, a concurrent, functional programming language specifically targeted
at building distributed systems. We argue that writing parallel simulation
models in Erlang is considerably easier than using conventional programming
languages. Moreover, ErlangTW allows simulation models to be executed either on
single-core, multicore and distributed computing architectures. We describe the
design and prototype implementation of ErlangTW, and report some preliminary
performance results on multicore and distributed architectures using the well
known PHOLD benchmark.
