CHOPtrey: contextual online polynomial extrapolation for enhanced multi-core co-simulation of complex systems

Abstract

The growing complexity of Cyber-Physical Systems (CPS), together with increasingly available parallelism provided by multi-core chips, fosters the parallelization of simulation. Simulation speed-ups are expected from co-simulation and parallelization based on model splitting into weak-coupled sub-models, as for instance in the framework of Functional Mockup Interface (FMI). However, slackened synchronization between sub-models and their associated solvers running in parallel introduces integration errors, which must be kept inside acceptable bounds.CHOPtrey denotes a forecasting framework enhancing the performance of complex system co-simulation, with a trivalent articulation. First, we consider the framework of a Computationally Hasty Online Prediction system (CHOPred). It allows to improve the trade-off between integration speed-ups, needing large communication steps, and simulation precision, needing frequent updates for model inputs. Second, smoothed adaptive forward prediction improves co-simulation accuracy. It is obtained by past-weighted extrapolation based on Causal Hopping Oblivious Polynomials (CHOPoly). And third, signal behavior is segmented to handle the discontinuities of the exchanged signals: the segmentation is performed in a Contextual & Hierarchical Ontology of Patterns (CHOPatt).Implementation strategies and simulation results demonstrate the framework ability to adaptively relax data communication constraints beyond synchronization points which sensibly accelerate simulation. The CHOPtrey framework extends the range of applications of standard Lagrange-type methods, often deemed unstable. The embedding of predictions in lag-dependent smoothing and discontinuity handling demonstrates its practical efficiency.

HintCO – Hint-based Configuration of Co-simulations

“…These restrictions imply that most state-of-theart algorithms relying on correction of signals (e.g., (Ben Khaled-El Feki et al, 2017, Benedikt et al, 2013,González et al, 2019) cannot be applied without some form of configuration.…”

Enhancing the Coupling of Real-Virtual Prototypes: A Method for Latency Compensation

“…One way to achieve this is to switch to the naïve ZOH algorithm whenever a discontinuity has occurred within the last m − 1 time step, while m is the number of past signal values the current coupling algorithm uses. The idea of switching the coupling algorithm based on specific signal properties is also pursued in offline co-simulations to reduce reconstruction errors [53]. Figure 6 shows an example of how discontinuity detection with coupling algorithm switching works.…”

Numerically robust co-simulation using transmission line modeling and the Functional Mock-up Interface

“…The technique is used in CHOPTrey, a forecasting framework for hybrid dynamic co-simulation. 11 However, this technique relies on slacked synchronization, which will always introduce some numerical errors and cannot provide guaranteed numerical stability for stiff connections.…”