Installation and build

ImmersX requires CMake 3.18 or newer, a C++ compiler supported by deal.II, and deal.II 9.7.1 or newer. MPI is required by the distributed applications. Optional deal.II components enable features such as VTK output, SUNDIALS time integration, SymEngine expressions, and PETSc or Trilinos backends.

Configure and build out of source:

cmake -S . -B build \
  -DCMAKE_BUILD_TYPE=Debug \
  -DDEAL_II_DIR=/path/to/deal.II \
  -DENABLE_GOOGLE_TESTING=ON \
  -DENABLE_DEAL_II_APP_TESTING=ON
cmake --build build -j

ImmersX supports Debug, Release, and DebugRelease. DebugRelease is a single-config build-tree mode that builds both variants at once: Release targets keep their normal names, while Debug targets receive the _debug suffix. It does not select a CMake multi-config generator.

cmake -S . -B build-debugrelease \
  -DCMAKE_BUILD_TYPE=DebugRelease \
  -DDEAL_II_DIR=/path/to/deal.II
cmake --build build-debugrelease -j

The optional lib1dsolver dependency enables the 3D/1D coupled_elasticity and pseudocoupling1D executables when it is available. The application reference lists dependencies and supported dimensions for every executable.

Point FVM_LIB at a complete library matching the vendored FVM headers, built with RTTI and with a compatible compiler, C++ standard-library ABI, MPI implementation, and system libraries. The backend’s USE_MPI setting changes the layout of its public classes. Match it explicitly with IMMERSX_FVM_USE_MPI: leave the option OFF (the default) for a serial backend, or select ON for a backend built with USE_MPI:

cmake -S . -B build-debugrelease \
  -DCMAKE_BUILD_TYPE=DebugRelease \
  -DENABLE_COUPLED_PROBLEMS=ON \
  -DFVM_LIB=/path/to/lib1dsolver.a \
  -DIMMERSX_FVM_USE_MPI=ON

The MPI setting requires deal.II with MPI. ImmersX applies the same definition to its link check and exports it to application and library consumers. The library filename cannot identify this ABI setting; a successful link alone does not prove that the backend and header layouts agree. The backend is an external dependency; ImmersX does not download or rebuild its sources.

The legacy drivers execute the 1D model on rank zero. The MPI-enabled backend uses MPI_COMM_WORLD internally and exposes no communicator argument, so the drivers reject coupled runs with that backend and more than one MPI rank. Distributed tissue coupling requires a matching serial 1D backend with IMMERSX_FVM_USE_MPI=OFF. The uncoupled 3D mode of coupled_elasticity remains available with multiple MPI ranks.

To build the published documentation, install the Python requirements and run:

python3 -m pip install -r doc/requirements.txt
./scripts/build_doc.sh

The site is generated in build/docs/site/. A configured CMake build also provides cmake --build build --target doc.