events are treated badly

[Lennart Ochel]

I attached four models to show why OpenModelica treats events badly:

  model test1 
    parameter Real p = 1.5; 
    Real t = if time < p then time else p; 
    Boolean d = t > p and t >= p; 
    Boolean e; 
  algorithm 
    e := true; 
    if t > p then 
      e := false; 
    end if; 
    annotation(experiment(StartTime = 0, StopTime = 3)); 
  end test1; 

test2 is equal to test1 but without variable d.
test3 is equal to test1 but with if t > p then as condition in the algorithm section.
test4 is equal to test3 but without variable d.

I attached also the simulation results of OpenModelica and Dymola for variable e of all four examples. I think Dymola handles the examples correctly. OpenModelica handles at least the first three examples different.

[Lennart Ochel]

I did some changes to the evaluation of zero crossings, which fix all the models mentioned above.

[Lennart Ochel]

The fix also uncovers more issues, so that I cannot commit it as it is right now.

[Francesco Casella]

My understanding is that this kind of model ultimately relies on the fact that the zeros of the zero-crossing functions are computed exactly, but in general you cannot rely on that, as it is impossible to represent exact solutions of Real equations on a finite-precision floating point representation.

[Lennart Ochel]

Replying to casella:

My understanding is that this kind of model ultimately relies on the fact that the zeros of the zero-crossing functions are computed exactly, but in general you cannot rely on that, as it is impossible to represent exact solutions of Real equations on a finite-precision floating point representation.

I agree. The model can be improved by applying noEvent to the if-condition that belongs to variable t:

  model test1 
    parameter Real p = 1.5; 
    Real t = if noEvent(time < p) then time else p; 
    Boolean d = t > p and t >= p; 
    Boolean e; 
  algorithm 
    e := true; 
    if t > p then 
      e := false; 
    end if; 
    annotation(experiment(StartTime = 0, StopTime = 3)); 
  end test1;

Therewith, t cannot get greater than p anyway. test1 and test2 are now working as expected.

[Martin Sjölund]

Milestone changed to 1.9.3 since 1.9.2 was released.

[Martin Sjölund]

Moved to new milestone 1.9.4

[Martin Sjölund]

Milestone pushed to 1.9.5

[Martin Sjölund]

Milestone renamed

[Martin Sjölund]

Ticket retargeted after milestone closed

[Martin Sjölund]

Milestone moved to 1.12.0 due to 1.11.0 already being released.

[Francesco Casella]

The milestone of this ticket has been reassigned to "Future".

If you think the issue is still valid and relevant for you, please select milestone 1.13.0 for back-end, code generation and run-time issues, or 2.0.0 for front-end issues.

If you are aware that the problem is no longer present, please select the milestone corresponding to the version of OMC you used to check that, and set the status to "worksforme".

In both cases, a short informative comment would be welcome.