MQT DDSIM is mainly developed as a C++ library that builds upon our decision diagram (DD) package as well as our quantum functionality representation (QFR). In order to make the tool as accessible as possible, it comes with an easy-to-use Python interface.


We encourage installing DDSIM via pip (preferably in a virtual environment):

(venv) $ pip install mqt.ddsim

In most practical cases (under 64-bit Linux, MacOS, and Windows), this requires no compilation and merely downloads and installs a platform-specific pre-built wheel.

However, in order to get the best performance out of DDSIM and enable platform-specific compiler optimizations that cannot be enabled on portable wheels, it is recommended to build the package from source via:

(venv) $ pip install mqt.ddsim --no-binary mqt.ddsim

This requires a C++ compiler supporting C++17, a minimum CMake version of 3.14 and OpenMP.

The library is continuously tested under Linux, MacOS, and Windows using the latest available system versions for GitHub Actions. In order to access the latest build logs, visit ddsim/actions/workflows/ci.yml.

Disclaimer: We noticed some issues when compiling with Microsoft’s MSCV compiler toolchain. If you want to start development on this project under Windows, consider using the clang compiler toolchain. A detailed description of how to set this up can be found here.


In order to start developing, clone the DDSIM repository using

$ git clone --recurse-submodules

Note the --recurse-submodules flag. It is required to also clone all the required submodules. If you happen to forget passing the flag on your initial clone, you can initialize all the submodules by executing git submodule update --init --recursive in the main project directory.

A C++ compiler supporting C++17, a minimum CMake version of 3.14 and OpenMP is required to build the project. The ddsim_noise_aware simulator further requires Threads::Threads.

Working on the core C++ library

Our projects use CMake as the main build configuration tool. Building a project using CMake is a two-stage process. First, CMake needs to be configured by calling

$ cmake -S . -B build -DCMAKE_BUILD_TYPE=Release

This tells CMake to search the current directory . (passed via -S for source) for a CMakeLists.txt file and process it into a directory build (passed via -B). The flag -DCMAKE_BUILD_TYPE=Release tells CMake to configure a Release build (as opposed to, e.g., a Debug build).

After configuring with CMake, the project can be built by calling

$ cmake --build build --config Release

This tries to build the project in the build directory (passed via --build). Some operating systems and developer environments explicitly require a configuration to be set, which is why the --config flag is also passed to the build command. The flag --parallel <NUMBER_OF_THREADS> may be added to trigger a parallel build.

Building the project this way generates

  • the main library libddsim.a (Unix) / ddsim.lib (Windows) in the build/src directory

  • a test executable ddsim_test containing unit tests in the build/test directory (this requires passing -DBUILD_DDSIM_TESTS=ON to CMake during configuration)

  • the Python bindings library pyddsim.<...> in the build/mqt/ddsim directory (this requires passing -DBINDINGS=ON to CMake during configuration)

Working on the Python module

The mqt.ddsim Python module can be conveniently built locally by calling

(venv) $ pip install --editable .

The --editable flag ensures that changes in the Python code are instantly available without re-running the command.

Pybind11 is used for providing bindings of the C++ core library to Python (see bindings.cpp). If parts of the C++ code have been changed, the above command has to be run again to make the changes visible in Python.