id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
4051	Add documentation for FMI 2.0 for CS	Francesco Casella	Adeel Asghar	"I am trying to understand how exactly do FMIs for CS generated from OMC work. Unfortunately, the man page 

https://openmodelica.org/doc/OpenModelicaUsersGuide/latest/fmi.html

doesn't tell much.

From the FMI specification, the function {{{fmi2DoStep()}}} only provides the current communication time and the length of the communication interval. It does not provide any hint to the solver so as to which algorithm is used and how many steps it should take. I assume this should then be determined at the time of FMI code generation, and possibly influenced by some API arguments and/or compiler flags.

Regarding API arguments, I looked up  https://build.openmodelica.org/Documentation/OpenModelica.Scripting.translateModelFMU.html and it seems there is no way to specify anything regarding the integration algorithm of FMIs for CS.

Regarding compiler flags, I googled the topic up and the only info I could find was in #3540, which says that currently only Euler is supported as simulation algorithm.

With this lack of info, one can try to understand how FMIs for CS generated by OMC work only by trial-and-error, which is an unnecessary waste of time. 

I would then strongly suggest to enhance the FMI documentation page https://openmodelica.org/doc/OpenModelicaUsersGuide/latest/fmi.html, by adding a section on FMIs for CS that addresses these questions explicitly:

- what are the implemented algorithms and how you select one?
- how can you choose the step-size between communication steps in the case of fixed time step algorithms?
- are internal events handled? If so, how?

Thanks!"	enhancement	closed	critical		FMI		fixed		gianluca.bardaro@…