CWIPI (Coupling With Interpolation Parallel Interface) is a library for coupling parallel scientific codes via MPI communications to perform multi-physics simulations in massively parallel, distributed-memory environments, with interfaces in C, Python and Fortran.

📖 Documentation

The user documentation is available either on the GitHub page or on ONERA's internal Gitlab.

🛠️ Build and install

Dependencies

General dependencies for building CWIPI are:

• a C++ compiler (tested with gcc 10, 12, 14, 15, 16, intel 2022, intel-llvm 2022, intel-llvm 2025)
• CMake (version 3.16 or higher)
• an MPI distribution (tested with openmpi and intel oneapi)

To run CWIPI tests with cwp_run, additional dependencies are:

• bc
• awk
• gnu-time on macOS

To build CWIPI Fortran API, additional dependencies are:

• a Fortran 90 compiler (tested with gfortran based on gcc 10, 12, 14, 15, 16, intel 2022, intel-llvm 2022, intel-llvm 2025)

To build CWIPI Python API, additional dependencies are:

• numpy (1.x)
• mpi4py
• Cython (0.29.x, 3.x)

Basic Installation

Follow these steps to build CWIPI from the sources:

First, clone the repository

• either from GitHub: git clone git@github.com:onera/cwipi.git
• or from GitLab (for ONERA users only): git clone git@gitlab.onera.net:numerics/coupling/cwipi.git

Then, use the following commands:

1. cd cwipi
2. git submodule update --init (needed for dependencies such as ParaDiGM)
3. mkdir build
4. cd build
5. cmake ..
6. make
7. make install
8. ./cwp_run (if you want to run the test cases, at least 10 CPU cores are required)

Configuration with CMake

CMake general options

cmake -D<option1_name>=<option1_value> ... -D<option2_name>=<option2_value>

Installation prefix

CMAKE_INSTALL_PREFIX=<prefix>

Enable Fortran interface

CWP_ENABLE_Fortran=<ON | OFF> (default : OFF)
CWP_ENABLE_Fortran_MPI_MODULE=<ON | OFF> (default : OFF)

Enable Python interface

CWP_ENABLE_PYTHON_BINDINGS=<ON | OFF> (default : OFF)

If a simple autodetection fails, you can use these options to find Python :

PYTHON_LIBRARY=<path>
PYTHON_INCLUDE_DIR=<path>

Refer to FindPython in the CMake documentation for more information.

Build shared library

CWP_ENABLE_SHARED=<ON | OFF> (default : ON)

Build static library

CWP_ENABLE_STATIC=<ON | OFF> (default : OFF)

Hide symbols of internal ParaDiGM library

CWP_ENABLE_HIDE_PDM_SYMBOLS=<ON | OFF> (default : ON)

If CWP_ENABLE_STATIC=ON then CWP_ENABLE_HIDE_PDM_SYMBOLS=OFF is forced

Enable the use of external ParaDiGM library

CWP_ENABLE_EXTERNAL_PDM=<ON | OFF> (default : OFF)

If CWP_ENABLE_EXTERNAL_PDM=ON, you must define this variable to find ParaDiGM:

PDM_SOURCE_DIR=<path> Where to find the base directory of ParaDiGM

If CWP_ENABLE_HIDE_PDM_SYMBOLS=ON then CWP_ENABLE_EXTERNAL_PDM=OFF is forced

🚀 Quick start

You can find a basic example of two-way coupling using CWIPI in the quick start section of the documentation. Additional examples for more advanced scenarios can be found in the tests directory.

🤕 Issues

Issues can be reported directly in the Issues section.

⚖️ License

CWIPI is available under the LGPL3 license.

© Copyright

Copyright 2026, ONERA The French Aerospace Lab