Cross-state events: A new approach to parallel discrete event simulation and its speculative runtime support

Abstract

We present a new approach to Parallel Discrete Event Simulation (PDES), where we enable the execution of so-called cross-state events. During their processing, the state of multiple concurrent simulation objects can be accessed in read/write mode, as opposed to classical partitioned accesses. This is done with no pre-declaration of this type of access by the programmer, hence also coping with non-determinism. In our proposal, cross-state events are supported by a speculative runtime environment fully transparently to the application code. This is done through an ad-hoc memory management architecture and an extension of the classical Time Warp synchronization protocol. This extension, named Event and Cross-State (ECS) synchronization, ensures causally-consistent speculative parallel execution of discrete event applications by allowing all events to observe the snapshot of the model execution trajectory that would have been observed in a timestamp-ordered execution of the same model. An experimental assessment of our proposal shows how it can significantly reduce the application development complexity, while also providing advantages in terms of performance.

Synchronous speculative simulation of tightly coupled agents in continuous time on CPUs and GPUs

“…Events are processed without a fixed mapping between threads and logical processes or simulation objects, while still avoiding conflicting state accesses. Pellegrini and Quaglia 40 presented a mechanism for transparent access to the state of arbitrary simulation objects in optimistic simulations. This is achieved by an operating system-level redirection of memory accesses.…”