Running FhSim from your own software

Table of Contents

• Which route should I take?
• Contents
• Minimal embedding workflow

FhSim can be driven from software you write yourself, instead of from the standalone executables. Three routes exist, and this section covers all three.

Which route should I take?

	Embed the shared library	Export an FMU	Run the standalone executable
Control granularity	Per step, or per slice of model time. The host sets inputs, advances, and reads outputs in its own loop.	Per co-simulation communication point, decided by the FMI master, not by you.	None during the run. The scenario runs start to finish.
Deployment model	Your program loads fhSimDll/fhVisDll from an FhSim installation at runtime.	A single .fmu file that bundles the FhSim binaries and resources it needs.	An FhSim installation plus your XML.
What the host must provide	C++ code that loads the library, and one System/ExternalLinkStandard object in the model for data exchange.	An FMI 2.0 co-simulation master. The model needs an ExternalLinkStandard object; FhFmuExport can synthesise one with --guess-input-interface / --guess-output-interface.	Nothing but the XML scenario. Results come out through the observers configured in it.
How results come out	Return values of the port and state calls, in process.	FMI variables read by the master.	Observer output files configured in the XML.
Limits	The host and the library must be built for the same platform and ABI.	FMI 2.0 co-simulation only. The exported FMU contains binaries only for the platform the exporter was built on, and only the 64-bit platforms are actively maintained.	No interaction with a host program.

Start here: if you only need results out of a scenario, use the standalone executable and an observer — see Running simulations. Add one of the API routes only when your own software has to be inside the loop. Of those two, embed the shared library when you own the host program and it is C++; export an FMU when the model has to plug into someone else's co-simulation tool.

Note

Both API routes exchange data through the same mechanism: a System/ExternalLinkStandard SimObject in the model, whose input ports the host writes and whose output ports the host reads. A model with no such object can be run, but not steered.

Contents

• Integrate FhSim in own applications — Load the shared library and drive the simulation from C++.
• FMU tools — Package a model as an FMI 2.0 co-simulation FMU.
• Linking FhSim with CMake — Which CMake target to link, and how to find it.
• OBSERVERS section — Configure what a run writes out.

Minimal embedding workflow

1. Load the runtime library.
2. Initialize from an XML file or an XML string.
3. Set the external input port values.
4. Advance the simulation.
5. Read outputs and states.
6. Stop and release the resources.