id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
4237	Bad treatment of algebraic loops in synchronous models	Rüdiger Franke	Willi Braun	"[https://github.com/OpenModelica/OMCompiler/pull/1391 PR1391] along with [https://github.com/OpenModelica/OMCompiler/commit/d32ecbb30f3cd8de9baad8576b1f9a1df0425ec3 commit d32ecb] make `ControlledMixingUnit` work by applying index reduction and appropriately implementing `ExplicitEuler`, respectively.

Some more issues show up when replacing `ExplicitEuler` with `ImplicitEuler`, introducing algebraic loops. See the following example:
{{{#!mo
model ControlledMixingUnit2
  extends Modelica_Synchronous.Examples.Systems.ControlledMixingUnit(
    periodicClock1(solverMethod=""ImplicitEuler""));
end ControlledMixingUnit2;
}}}

No Jacobians and no ModelStructure are generated!

Moreover, there is a linear torn system of dimension 1 -- shouldn't this be solved analytically?

Last but not least, the C runtime does not generate code for algebraic loops in clocked partitions.
"	defect	closed	high	1.13.0	Backend	v1.12.0	fixed		Willi Braun Bernhard Thiele Patrick Täuber