TY - CONF CY - ICST, Brussels, Belgium, Belgium Y1 - 2013/// A1 - Bortolussi, Luca A1 - Tribastone, Mirco PB - ICST (Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering) T3 - ValueTools '13 SP - 49 ID - eprints2962 EP - 58 T2 - Proceedings of the 7th International Conference on Performance Evaluation Methodologies and Tools AV - none TI - Differential Analysis of Interacting Automata with Immediate Actions KW - differential equations KW - immediate actions KW - time-scale separation UR - http://dx.doi.org/10.4108/icst.valuetools.2013.254364 M2 - Torino SN - 978-1-936968-48-0 N2 - 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. ER -