Ecos

Ecos is a co-simulation engine.

Ecos (Easy co-simulation) is a fast, efficient and very easy to use co-simulation engine written in modern C++.

Ecos provides the following features:

• FMI for Co-simulation version 1.0 & 2.0
• SSP version 1.0
• Optional sandboxed/remote model execution
• Post-simulation plotting using matplotlib
• Command-line-interface (CLI)
• Simplified Python and C interface

Building

Ecos relies on vcpkg to handle dependencies.

Once installed, please add the entry VCPKG_ROOT to PATH pointing your /vcpkg folder. Alternatively, call CMake with -DCMAKE_TOOLCHAIN_FILE=[path to vcpkg]/scripts/buildsystems/vcpkg.cmake.

Example:

//windows
cmake . -A x64 -B build -DCMAKE_TOOLCHAIN_FILE="C:/vcpkg/scripts/buildsystems/vcpkg.cmake" -DECOS_BUILD_EXAMPLES=ON -DECOS_BUILD_TESTS=ON -DCMAKE_BUILD_TYPE=Release
cmake --build build --config Release

//linux
cmake . -B build -DCMAKE_TOOLCHAIN_FILE="/home/user/vcpkg/scripts/buildsystems/vcpkg.cmake" -DECOS_BUILD_EXAMPLES=ON -DECOS_BUILD_TESTS=ON -DCMAKE_BUILD_TYPE=Release
cmake --build build

Notes on static linking and vcpkg (windows)

In order to produce executables with no DLL dependencies on windows, you need to call CMake with -DVCPKG_TARGET_TRIPLET=x64-windows-static-md

Example

using namespace ecos;

int main() {
    
    simulation_structure ss;

    // add models
    ss.add_model("chassis", "chassis.fmu");
    ss.add_model("ground", "ground.fmu");
    ss.add_model("wheel", "wheel.fmu");
    
    //make connections
    ss.make_connection<double>("chassis::p.e", "wheel.p1::e");
    ss.make_connection<double>("wheel::p1.f", "chassis.p::f");
    ss.make_connection<double>("wheel::p.e", "ground.p::e");
    ss.make_connection<double>("ground::p.f", "wheel.p::f");
    
    // setup initialValues
    std::map<variable_identifier, scalar_value> map;
    map["chassis::C.mChassis"] = 4000.0;
    ss.add_parameter_set("initialValues", map);
    
    auto sim = ss.load(std::make_unique<fixed_step_algorithm>(1.0 / 100), "initialValues");
    
    sim->init();
    sim->step_until(10);
    
    sim->terminate();
}

SSP example

using namespace ecos;

int main() {
    
    auto ss = load_ssp("quarter-truck.ssp");

    // use a fixed-step algorithm and apply parameterset from SSP file
    auto sim = ss->load(std::make_unique<fixed_step_algorithm>(1.0 / 100), "initialValues");
    
    // setup csv logging
    csv_config config;
    config.register_variable("chassis::zChassis"); // logs a single variable
    
    auto csvWriter = std::make_unique<csv_writer>("data.csv", config);
    csvWriter->enable_plotting("ChartConfig.xml"); // enable post-simulation plotting
    sim->add_listener(std::move(csvWriter));
    
    sim->init();
    sim->step_until(10);
    
    sim->terminate();
}

Command line interface

Options:
  -h [ --help ]                 Print this help message and quits.
  -v [ --version ]              Print program version.
  -i [ --interactive ]          Make execution interactive.
  -l [ --logLevel ] arg (=info) Specify log level [trace,debug,info,warn,err,of
                                f].
  --path arg                    Location of the fmu/ssp to simulate.
  --stopTime arg (=1)           Simulation end.
  --startTime arg (=0)          Simulation start.
  --stepSize arg                Simulation stepSize.
  --rtf arg (=-1)               Target real time factor (non-positive number ->
                                inf).
  --noLog                       Disable CSV logging.
  --noParallel                  Run single-threaded.
  --logConfig arg               Path to logging configuration.
  --chartConfig arg             Path to chart configuration.
  --scenarioConfig arg          Path to scenario configuration.

Python interface

To use the python interface, simply clone the project and run:

pip install ./ecospy

See here for an example.

Note: if using an old pip version, append --use-feature=in-tree-build if you get an error about ../version.txt

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Compile-time requirements

• Windows (10 >=) or Ubuntu (20.04 >=)
• C++17 compiler (MSVC >= 16 || gcc9 >=)
• CMake >= 3.17
• Vcpkg

Additional Linux requirements

sudo apt install libtbb-dev

Run-time requirements

• Python3 (required for plotting)
  • matplotlib
  • pandas

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Want to build FMUs in C++? Check out FMU4cpp
Want to build FMUs in Kotlin/Java? Check out FMU4j
Want to build FMUs in Python? Check out PythonFMU
SSP generation made easy? Check out SSPgen