Wrong numerical handling of conditional equations

[casella]

Please simulate the attached test model.

The variable s, which is the result of a double integration, crosses the zero threshold at time = 0.1.

Based on the equations, the variable Pw should be zero until that moment, and then start growing afterwards. The result reported in the attached figure is instead obtained:

• at the previous time step (time = 0.0741), Pw is zero
• at time = 0.1 before the event, Pw is shown to be 0.05
• at time = 0.1 after the event, Pw is again zero as it should be

The value of Pw just before the event is totally bogus. I'm not sure if this is a problem with the solver or with the result file generation.

[wbraun]

It seems that the model doesn't fit to the plot, since it contains only variable x.

[casella]

Correct .mo file

[casella]

Sorry, of course I attached the wrong foo.mo

[lochel]

I cannot reproduce your signals, please see ticket4254.png.

[lochel]

Okay, now I can reproduce the signals. For some reason the simulationFlags annotation got not considered.

[casella]

Aha, it seems it's the noEquidistantTimeGrid flag

[lochel]

Replying to casella:

Aha, it seems it's the noEquidistantTimeGrid flag

Well, not really. If you omit that flag, then the difference is still present, but you have to zoom in to see the difference.

[casella]

Right. With equidistantTimeGrid the last step before the event is much longer, so the effect is much bigger. Maybe that is a useful clue?

[wbraun]

As far as I see, this is connected to #3851, since it's seems that the linear algebraic system evaluate a zerocrossing literally.

[wbraun]

Fixed in ​PR2726.

[casella]

Replying to wbraun:

Fixed in ​PR2726.

Thanks Willi!