Implementing SOS with Active Objects: A Case Study of a Multicore Memory System

Abstract

This paper describes the development of a parallel simulator of a multicore memory system from a model formalized as a structural operational semantics (SOS). Our implementation uses the Abstract Behavioral Specification (ABS) language, an executable, active object modelling language with a formal semantics, targeting distributed systems. We develop general design patterns in ABS for implementing SOS, and describe their application to the SOS model of multicore memory systems. We show how these patterns allow a formal correctness proof that the implementation simulates the formal operational model and discuss further parallelization and fairness of the simulator.Supported by SIRIUS: Centre for Scalable Data Access (www.sirius-labs.no) and ADAPt: Exploiting Abstract Data-Access Patterns for Better Data Locality in Parallel Processing (www.mn.uio.no/ifi/english/research/projects/adapt/).

Active Objects with Deterministic Behaviour

“…In addition, Encore supports an advanced capability-based type system [20] which enables race-free data sharing between active objects. Confluence properties for cooperative scheduling in ABS have previously been studied, based on controlling the local scheduler [21,22].…”

From SOS to Asynchronously Communicating Actors

“…The correctness of the decentralized active object implementation of the SOS model can then be addressed by a simulation relation between the ABS code and the transitions of the SOS model. This approach is based on the notion of stable points in the execution of ABS programs [5], at which an object requires external input to make progress (either an event or a scheduling decision). The semantics of ABS then allows us to prove that executions are globally confluent at the granularity of stable points [5,6].…”

“…This approach is based on the notion of stable points in the execution of ABS programs [5], at which an object requires external input to make progress (either an event or a scheduling decision). The semantics of ABS then allows us to prove that executions are globally confluent at the granularity of stable points [5,6]. Consequently, it is sufficient to reason about one object at a time between stable points in the program execution.…”

“…This paper is an extended abstract of an invited talk given at FOCLASA 2019. Further details of the ideas discussed in this paper may be found in [5,6] and the source of the original SOS model which triggered our interest in this line of investigation may be found in [7].…”

Global Reproducibility Through Local Control for Distributed Active Objects

“…The proposed method to deterministically replay runs has been realized for Real-Time ABS [6], a modeling language with these advanced features, which has been used to analyze, e.g., industrial scale cloud-deployed software [7], railway networks [8], and complex low-level multicore systems [9,10]. Whereas the language supports various formal analysis techniques, most validation of complex models (at least in an early stage of model development) is based on simulation.…”