id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
3491	Back-end time scales very badly for large system with very simple structure	Francesco Casella	Lennart Ochel	"Please consider the back-end times for the models {{{ScalableTestSuite.Thermal.DistrictHeating.ScaledExperiments.HeatingSystem_N_XXX}}}. 

The structure of the system is extremely simple: index 1, no algebraic loops, very sparse Jacobian of the state derivative functions (most state derivatives depend on just 3 states). It shouldn't be too hard for the back-end structural analysis algorithms to find this out quickly.

The back-end time scales as O(N) up to size 40 (about 80 states). Then it scales as O(N^2^) up to size 160. Then, for larger sizes, it starts growing as O(N^3.5^) (!), so it already takes 20 minutes for a system with a mere 1200 states.

Give the extremely simple structure of the system I really see no reason why this should happen. Some basic profiling should quickly reveal which part of the back-end goes wrong."	defect	closed	high		Backend		fixed		Adrian Pop Willi Braun andrea.bartolini@… Vitalij Ruge