I have some test simulations that, when run, do not follow the exact same solution path when run in Dymola 2021x and Dymola 2022. Thus, my system that checks to make sure my test simulations are running properly indicates that they are in fact not running properly. It appears that the simulations are still within +/-2*tolerance of each other. I am attempting to learn why it would be that the solutions are not numerically identical if they inputs and models are identical. Nothing in the update release indicated that there were any solution method changes.
1 Answers
From the Dymola 2022 Release Notes, one possible explanation could be in the different Modelica Language Specifications (3.4 in Dymola 2021x, 3.5 in Dymola 2022), either affecting the models directly (MSL 4.0.0 is compliant with the Language Specification 3.4, for example), or the way the models are handled during translation.
You mention you have a system in place that checks your simulation. Is it implemented in Modelica, that is, might it be affected by the different Language Specifications?
Personally, I tend to expect in each release minor changes/improvements in the translation algorithms and in the solvers; even though they might not be mentioned in the release notes. Perhaps this attitude only works because my models are rather coarse, so I cannot really say whether such a change in the computed solution (+-2*tolerance, tolerance=0.1% in my case) is bringing me closer or farther away from the real solution.
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