fortress

Fortress is a set of modern Fortran components for Bayesian time–series estimation and the tooling required to expose those components to Python. The project serves two audiences:

• Python users who install the package and call the high-level API/CLI that scikit-build-core produces.
• Fortran developers who want a reusable library (modules plus static/shared libraries) that can be consumed from another CMake build.

This guide covers installation, testing, and integrating Fortress into an external Fortran project.

---

Installation

Fortress uses scikit-build-core and honours CMake cache options. The two most common workflows are:

Python / pip

# Serial build (default)
pip install fortress

# Enable MPI/OpenMP support
ENABLE_MPI=ON ENABLE_OPENMP=ON pip install fortress

If you prefer pip’s configuration interface (>=23.1), you can pass the flags as --config-settings, for example:

pip install fortress --config-settings=cmake.define.ENABLE_MPI=ON

The same options work with uv sync/uv pip; the repository already documents uv sync --config-settings=cmake.define.ENABLE_MPI=ON as the canonical editable workflow.

From source (developer)

uv sync --config-settings=cmake.define.ENABLE_MPI=ON \
        --config-settings=cmake.define.BUILD_FORTRAN_TESTS=ON
uvx --from cmake cmake -S . -B build -DENABLE_MPI=ON
uvx --from cmake cmake --build build

If you installed CMake ≥3.21 via another route, swap the uvx --from cmake calls for your local executable.

---

Testing

The project registers its Fortran unit suite as fortress_unit_tests inside the CMake tree. After configuring and building (as above) run:

uvx --from cmake ctest --test-dir build

The suite defaults to the MPI-enabled executables when ENABLE_MPI=ON. When MPI is disabled the tests that rely on mpif.h will be skipped automatically.

---

Using Fortress as a Fortran Dependency

Fortress installs both static and shared libraries together with Fortran module files and a CMake package configuration. After running cmake --install . (or installing the built wheel), an external CMake project can integrate Fortress in either of two ways:

find_package

# CMakeLists.txt in your project
find_package(fortress CONFIG REQUIRED)          # add -Dfortress_ROOT=/path/to/install if needed

add_executable(example main.f90)
target_link_libraries(example PRIVATE fortress::fortress_static)

# Optional: request the shared library instead
# target_link_libraries(example PRIVATE fortress::fortress_shared)

Provide -Dfortress_ROOT=/install/prefix or extend CMAKE_PREFIX_PATH if the package is not in a default search location.

FetchContent

include(FetchContent)

FetchContent_Declare(
  fortress
  GIT_REPOSITORY https://github.com/eph/fortress.git   # or point at your local clone
  GIT_TAG main
)
FetchContent_MakeAvailable(fortress)

add_executable(example main.f90)
target_link_libraries(example PRIVATE fortress::fortress_static)

To switch between a local checkout and GitHub just update the GIT_REPOSITORY (or override FetchContent_SOURCE_DIR_fortress). Compile-time options propagate normally: pass -DENABLE_MPI=ON/OFF when configuring your top-level project and Fortress will rebuild accordingly.

---

Frequently Used CMake Options

• ENABLE_MPI – build MPI-aware components (OFF by default).
• ENABLE_OPENMP – enable OpenMP parallelism when MPI is not available (ON by default, auto-disables if the compiler lacks OpenMP support).
• BUILD_FORTRAN_TESTS – compile the FRUIT-based test driver and register it with CTest; useful when packaging or running CI from the source tree.