UniFMU - Universal Functional Mock-Up Units

The Functional Mock-Up Interface (FMI) defines an exchange format that allows models, referred to as Functional Mock-Up Unit (FMU), to be shared between tools supporting the standard. In general, an FMU must be implemented in a programming language that can produce binaries that can be called from C, such as C itself or C++. While this allows efficient execution of a simulation, it is a significant limitation when prototyping models.

UniFMU is a command line tool that facilitates the implementation of FMUs in other popular languages that would otherwise not be able to produce C-compatible binaries. It does this by providing a precompiled binary that is C-compatible, which then dispatches calls to the implementation of the model in the target language.

Specification Version	FMU Interface	Languages	Binaries
FMI3 (in progress)	(Co-Simulation)	(Python, C#, Java)	(win64, linux64, darwin64)
FMI2	Co-Simulation	Python, C#, Java	win64, linux64, darwin64
FMI1	x	x	x

Examples of generated FMUs can be found in the unifmu_examples repo.

Getting the tool

The tool can be downloaded from releases tab of the repository. It is a single executable that bundles all assets used during FMU generation as part of the binary.

How to use the command line interface?

To display the synopsis use the --help flag.

unifmu 0.0.8

Implement Functional Mock-up units (FMUs) in various source languages.

* Source:   https://github.com/INTO-CPS-Association/unifmu
* Examples: https://github.com/INTO-CPS-Association/unifmu_examples

USAGE:
    unifmu <SUBCOMMAND>

OPTIONS:
    -h, --help       Print help information
    -V, --version    Print version information

SUBCOMMANDS:
    generate     Create a new FMU using the specified source language
    help         Print this message or the help of the given subcommand(s)

The command uses git-style subcommands, an example being generate. Help for the individual commands can be inquired by appending the --help after the name of the subcommand.

Create a new FMU using the specified source language

USAGE:
    unifmu generate [OPTIONS] <LANGUAGE> <FMU_VERSION> <OUTPATH>

ARGS:
    <LANGUAGE>       Source language of the generated FMU [possible values: python, c-sharp, java]
    <FMU_VERSION>    Version of the FMI specification to target [possible values: fmi2, fmi3 (in progress)]
    <OUTPATH>        Output directory or name of the FMU archive if "--zipped" is passed

OPTIONS:
    -h, --help      Print help information
    -z, --zipped    Compress the generated FMU as a zip-archive and store with '.fmu' extension

The generate command can be used to create a new FMU:

unifmu generate python model

The command generates a placeholder FMU implemented in the specific language. For example the tree below shows the placeholder FMU generated when implementing an FMU in python using UniFMU:

📦model
 ┣ 📂binaries
 ┃ ┣ 📂darwin64
 ┃ ┃ ┗ 📜unifmu.dylib
 ┃ ┣ 📂linux64
 ┃ ┃ ┗ 📜unifmu.so
 ┃ ┗ 📂win64
 ┃ ┃ ┗ 📜unifmu.dll
 ┣ 📂resources
 ┃ ┣ 📂schemas
 ┃ ┃ ┗ 📜fmi2_messages_pb2.py
 ┃ ┣ 📜backend.py
 ┃ ┣ 📜launch.toml
 ┃ ┣ 📜model.py
 ┃ ┗ 📜README.md
 ┗ 📜modelDescription.xml

Language specific documentation

Like the file structure, the workflow for modifying FMUs varies depending on the implementation language. Depending on the language a README.md is placed in the root of the generated FMU, which serves as documentation for the particular language. For reference the README.md copied into Python FMUs looks like README.md.

Supported Features

FMI2

Name	Supported	Notes
fmi2GetTypesPlatform	✓
fmi2GetVersion	✓
fmi2SetDebugLogging	x
fmi2Instantiate	✓
fmi2FreeInstance	✓
fmi2SetupExperiment	✓
fmi2EnterInitializationMode	✓
fmi2ExitInitializationMode	✓
fmi2Terminate	✓
fmi2Reset	✓
fmi2GetReal	✓
fmi2GetInteger	✓
fmi2GetBoolean	✓
fmi2GetString	✓
fmi2SetReal	✓
fmi2SetInteger	✓
fmi2SetBoolean	✓
fmi2SetString	✓
fmi2GetFMUstate	✓
fmi2SetFMUstate	✓
fmi2FreeFMUstate	✓
fmi2SerializedFMUstateSize	✓
fmi2SerializeFMUstate	✓
fmi2DeSerializeFMUstate	✓
fmi2GetDirectionalDerivative	x
fmi2EnterEventMode	x
fmi2NewDiscreteStates	x
fmi2EnterContinuousTimeMode	x
fmi2CompletedIntegratorStep	x
fmi2SetTime	x
fmi2SetContinuousStates	x
fmi2GetDerivatives	x
fmi2GetEventIndicators	x
fmi2GetContinuousStates	x
fmi2GetNominalsOfContinuousStates	x
fmi2SetRealInputDerivatives	x
fmi2GetRealOutputDerivatives	x
fmi2DoStep	✓
fmi2CancelStep	x
fmi2GetStatus	x
fmi2GetRealStatus	x
fmi2GetIntegerStatus	x
fmi2GetBooleanStatus	x
fmi2GetStringStatus	x

FMI3 (in progress)

Name	Supported	Notes
fmi3GetVersion	✓
fmi3SetDebugLogging	x
fmi3InstantiateModelExchange	x
fmi3InstantiateCoSimulation	✓
fmi3InstantiateScheduledExecution	x
fmi3FreeInstance	✓
fmi3EnterInitializationMode	✓
fmi3ExitInitializationMode	✓
fmi3EnterEventMode	x
fmi3Terminate	✓
fmi3Reset	✓
fmi3GetFloat32	✓
fmi3GetFloat64	✓
fmi3GetInt8	✓
fmi3GetUInt8	✓
fmi3GetInt16	✓
fmi3GetUInt16	✓
fmi3GetInt32	✓
fmi3GetUInt32	✓
fmi3GetInt64	✓
fmi3GetUInt64	✓
fmi3GetBoolean	✓
fmi3GetString	✓
fmi3GetBinary	✓
fmi3GetClock	✓
fmi3SetFloat32	✓
fmi3SetFloat64	✓
fmi3SetInt8	✓
fmi3SetUInt8	✓
fmi3SetInt16	✓
fmi3SetUInt16	✓
fmi3SetInt32	✓
fmi3SetUInt32	✓
fmi3SetInt64	✓
fmi3SetUInt64	✓
fmi3SetBoolean	✓
fmi3SetString	✓
fmi3SetBinary	✓
fmi3SetClock	x
fmi3GetNumberOfVariableDependencies	x
fmi3GetVariableDependencies	x
fmi3GetFMUState	✓
fmi3SetFMUState	✓
fmi3FreeFMUState	✓
fmi3SerializedFMUStateSize	✓
fmi3SerializeFMUState	✓
fmi3DeserializeFMUState	✓
fmi3GetDirectionalDerivative	x
fmi3GetAdjointDerivative	x
fmi3EnterConfigurationMode	x
fmi3ExitConfigurationMode	x
fmi3GetIntervalDecimal	x
fmi3GetIntervalFraction	x
fmi3GetShiftDecimal	x
fmi3GetShiftFraction	x
fmi3SetIntervalDecimal	x
fmi3SetIntervalFraction	x
fmi3SetShiftDecimal	x
fmi3SetShiftFraction	x
fmi3EvaluateDiscreteStates	x
fmi3UpdateDiscreteStates	x
fmi3EnterContinuousTimeMode	x
fmi3CompletedIntegratorStep	x
fmi3SetTime	x
fmi3SetContinuousStates	x
fmi3GetContinuousStateDerivatives	x
fmi3GetEventIndicators	x
fmi3GetContinuousStates	x
fmi3GetNominalsOfContinuousStates	x
fmi3GetNumberOfEventIndicators	x
fmi3GetNumberOfContinuousStates	x
fmi3EnterStepMode	x
fmi3GetOutputDerivatives	x
fmi3DoStep	x
fmi3ActivateModelPartition	x

Building and deployment

Building during development

Building for local machine (with Windows as the example). This is a good method to locally test if the program is running as it should, before cross-compiling to different OSs.

1. make sure you have the following installed on your computer:

   o rust

   o a C-compiler and linker

2. git clone the unifmu repository.

3. make the changes you want.

4. install the rust toolchain for your operating systems, e.g. rustup target add x86_64-pc-windows-msvc (msvc is the microsoft C-compiler).

5. build the project using cargo build --target x86_64-pc-windows-msvc --release. This should build the project for your operating system, and generate a unifmu.exe in the folder target/release.

Building for deployment

This method should be followed when building the tool to be deployed for different OSs (windows, macos, linux).

1. you need to have gone through the steps in the previous instructions for the development build.

2. have docker installed on your computer.

3. build the docker image using docker build -t unifmu-docker docker-build. unifmu-docker is the name of the container, and docker-build is the directory where the Dockerfile is (assuming you are running this command from the root of the unifmu repository).

4. build the unifmu project in docker using docker run --name builder -it -v <location_of_unifmu_repository_on_local_pc>:/workdir unifmu-docker. This should generate three folders in the target directory on your local computer, one folder for each OS (windows, macos, linux).

Citing the tool

When citing the tool, please cite the following paper:

• Legaard, C. M., Tola, D., Schranz, T., Macedo, H. D., & Larsen, P. G. (2021). A Universal Mechanism for Implementing Functional Mock-up Units. In G. Wagner, F. Werner, T. I. Ören, & F. D. Rango (Eds.), Proceedings of the 11th International Conference on Simulation and Modeling Methodologies, Technologies and Applications, SIMULTECH 2021, Online Streaming, July 7-9, 2021 (pp. 121-129). SCITEPRESS Digital Library. https://doi.org/10.5220/0010577601210129

Bibtex:

@inproceedings{Legaard2021,
  title = {A Universal Mechanism for Implementing Functional Mock-up Units},
  booktitle = {11th {{International}} Conference on Simulation and Modeling Methodologies, Technologies and Applications},
  author = {Legaard, Christian M. and Tola, Daniella and Schranz, Thomas and Macedo, Hugo Daniel and Larsen, Peter Gorm},
  year = {2021},
  pages = {to appear},
  address = {{Virtual Event}},
  series = {{{SIMULTECH}} 2021}
}