%0 Conference Paper
%A Bortolussi, Luca
%A Tribastone, Mirco
%B Proceedings of the 7th International Conference on Performance Evaluation Methodologies and Tools
%C Torino
%D 2013
%F eprints:2962
%I ICST (Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering)
%K differential equations, immediate actions, time-scale separation
%P 49-58
%T Differential Analysis of Interacting Automata with Immediate Actions
%U http://eprints.imtlucca.it/2962/
%X The stochastic modelling of software systems with activities of durations that are separated by many orders of magnitude typically leads to numerical complications, due to stiffness. To avoid explicit state-space generation-a prerequisite to tackle this problem via suitable manipulations or aggregations-in this paper we present an accurate and scalable fluid approximation. It is expressed as a compact piecewise linear system of ordinary differential equations, which have discontinuous right-hand sides as a result of the incorporation of immediateness. We study the nature of this approximation in a general high-level framework of interacting automata. On a case study of client/server interaction, our approach is ca two times faster than the analysis conducted on the stiff equations where immediate actions are explicitly modelled.