FhSim

FhSim is a software tool and API for describing and simulating dynamic systems in the time domain. Systems are formulated as ordinary differential equations (ODEs), and FhSim provides multiple integration routines, optional 3D visualisation, and a plugin architecture for reusable simulation models called SimObjects.

A simulation is defined in terms of SimObjects, their parameters and interconnections. SimObjects are compiled into shared libraries and loaded at runtime. The simulation scenario — which objects to use, how they connect, and how the integrator runs — is described in an XML input file.

Which path is mine?

I want to…	Start here
Install FhSim and see it produce a result	Quick start — five minutes, self-contained
Run a model somebody else wrote	Running simulations, then Available model libraries
Write my own scenario XML against an existing model library	The FhSim input file
Know what units a number in the XML is in	Units and coordinate conventions
Write a new SimObject in C++	Setup developer environment, then Create a new SimObject
Call FhSim from my own program	Running FhSim from your own software
Fix an error message	Troubleshooting and Runtime errors and diagnostics
Upgrade a model from FhSim 2.x	Migrating to FhSim 3.0

Note

Writing a SimObject, and all but one of the Tutorials, require a C++ developer toolchain and a source build — an installer-only installation cannot follow them. Screenshots, videos and camera control is the exception: it needs only FhVis and an installed model library. Everything under Getting started, Running simulations and The FhSim input file works from an installer installation alone.

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• Getting started — Get installed and run your first simulation.
• Running simulations — Run simulations with existing model libraries.
• The FhSim input file — The FhSim XML input file format.
• Running FhSim from your own software — Drive a simulation from code you write yourself: the shared library, an exported FMU, or the standalone executable.
• Model development — Develop SimObjects and model libraries.
• Tutorials — Hands-on tutorials.
• Reference and appendix — Cheat sheet, troubleshooting, and migration notes.
• Review issues — fhsim — Known review issues in the FhSim core.

  Review issues:

  0070 — FhSimUI segfaults after it reports a failed render system initialisation

  0119 — A stop request is not polled for a step that produced no data

  0147 — The NetworkRoundTrip tests bind fixed TCP ports and collide when two runs overlap

  0148 — -o is ignored without a word for a Replay or Network provider without OBSERVERS

  0072 — A Debug build with visualization leaves about 148 GB of test FMUs in its build folder

  0073 — The v3 migration guide and the tutorial pages miss what porting fhsim_tutorial and fhsim_maritime needed

  0074 — RK45_i gains energy in an under-resolved contact where v2 did not

  0108 — A licence file cut by more than the writer's header padding loses its last entry without an error

  0113 — An empty `` is exported as a Real parameter with no values

  0115 — The FMU exporter reads `Size_<port>` with `std::stoi`, so `Size_y="2x"` reads 2

  0167 — An FMU does not tell the master that a model asked to stop

  0152 — AcceptedStep and the diagnostics read the last solver iterate under SUNDIALS

  0174 — BackwardEuler_i has no switch to a numeric Jacobian

  0175 — The self-connection check misses other users of the model Jacobian