Start value for final parameters with fixed=false is ignored

[Francesco Casella]

Consider the following model (also attached)

model TestInitStart
  final parameter Real p(start = p_start, fixed = false);
  parameter Real p_start = -2;
initial equation
 (p - 1)*p*(p+2) = 0;
annotation(__OpenModelica_simulationFlags(lv=LOG_NLS_V));
end TestInitStart;

The Newton solver log clearly shows that the iterations start at p = 0, not at p = -2 as expected, leading the convergence to the wrong solution.

This issue is preventing me to initialize in steady-state the big power plant model that I will present at the OpenModelica Workshop next week, so fixing this issue is currently top priority to show that OpenModelica can handle such real-life, complex models effectively.

[Francesco Casella]

Update: I just found a workaround: if I add -d=evaluateAllParameters, then the model works as expected.

Maybe gives you some clues so as to how to fix the issue.

Unfortunately I cannot use this workaround of the big model because it causes a new frontend failure related to homotopy. Life's hard.

[Karim Adbdelhak]

It seems like the compiler drops all fixed=false start values. That is correct for general initialization (in the sense that no initial equation is generated) but not for solving loops in the initialization problem.

I have a pretty good idea where to look!

[Lennart Ochel]

This might be synchronized with the OpenModelica FMI 2.0 export. There are strict rules for start values defined. Sounds bad to implement it twice.