Yggdrasil

pyyggdrasil packages the native dependency prefix used by the planning projects in this repository family.

The Python distribution name and import package are both pyyggdrasil.

pyyggdrasil is the base of the planning-and-learning package chain. The shared workspace layout, the layered install order, and the common build-from-source and CMake-integration patterns are documented in the Planning and Learning build instructions; the sections below cover pyyggdrasil-specific details.

Python Integration

Install the wheel and query the native prefix:

import pyyggdrasil

print(pyyggdrasil.native_prefix())
print(pyyggdrasil.cmake_prefix())  # prefix to put on CMAKE_PREFIX_PATH
print(pyyggdrasil.cmake_dir())     # directory containing yggdrasilConfig.cmake
print(pyyggdrasil.include_dir())
print(pyyggdrasil.library_dirs())
print(pyyggdrasil.cmake_dirs())

The same paths are available from the shell:

python -m pyyggdrasil --prefix
python -m pyyggdrasil --cmake-dir
python -m pyyggdrasil --include-dir
python -m pyyggdrasil --version

Python packages that consume this native prefix should depend on:

dependencies = [
    "pyyggdrasil>=0.0.27,<0.1",
]

The bundled shared libraries make the coupling ABI-level, so pin to the same minor version. The exported CMake package version file uses SameMinorVersion compatibility accordingly.

Build Python

Build a wheel from source:

uv build --wheel

The build creates dependencies-build/ and dependencies-install/. To package an existing native prefix without rebuilding dependencies:

YGGDRASIL_BUILD_NATIVE=OFF \
YGGDRASIL_NATIVE_PREFIX=/path/to/dependencies-install \
uv build --wheel

Native builds use all available processors by default. Set YGGDRASIL_JOBS to override the build parallelism. Set YGGDRASIL_BUILD_TYPE to select the dependency build profile; it defaults to Release.

Runtime libraries are stripped in the wheel by default. Disable that for debugging with:

YGGDRASIL_STRIP_WHEEL=OFF uv build --wheel

Build C++

Native Dependencies

Build the native dependency prefix directly with CMake:

cmake -S src -B dependencies-build \
  -DCMAKE_INSTALL_PREFIX=dependencies-install \
  -DCMAKE_INSTALL_LIBDIR=lib

cmake --build dependencies-build --parallel
cmake --install dependencies-build

Yggdrasil builds its bundled dependencies as shared libraries. The native dependency prefix contains C++ headers, shared libraries, and CMake package configuration files consumed by the other projects.

Yggdrasil Targets

Configure Yggdrasil separately against the installed dependency prefix:

cmake -S . -B build \
  -DCMAKE_BUILD_TYPE=Debug \
  -DYGGDRASIL_NATIVE_PREFIX="$PWD/dependencies-install" \
  -DYGGDRASIL_BUILD_TESTS=ON

cmake --build build --parallel
ctest --test-dir build

CMake options:

Single-config CMake builds default to Release. On GCC and Clang, Debug builds use -Og with debug symbols, RelWithDebInfo keeps frame pointers and disables LTO, and Release LTO uses GCC LTO or Clang ThinLTO. Editable installs and wheels disable YGGDRASIL_USE_LLD and YGGDRASIL_ENABLE_LTO by default for build reliability. This compiler policy applies only to Yggdrasil's first-party extension and tests; the src/ dependency superbuild leaves each bundled project in control of its own compiler policy.

CMake Integration

The wheel ships a CMake package config (yggdrasilConfig.cmake) defining the yggdrasil::yggdrasil interface target. It carries the include directory, C++20 as a compile feature, and the bundled dependencies (Boost, fmt, gtl, TBB) via find_dependency. (cista is consumed through the include directory only — its target exports compile definitions that would otherwise change cista's hashing and fmt integration.) Downstream CMake projects consume it through CMAKE_PREFIX_PATH:

cmake -S . -B build \
  -DCMAKE_PREFIX_PATH="$(python -m pyyggdrasil --prefix)"

find_package(yggdrasil 0.0.27 CONFIG REQUIRED)
target_link_libraries(my_target PRIVATE yggdrasil::yggdrasil)

For compiler invocations launched from Python, use pyyggdrasil.include_dir() for the C++ headers and pyyggdrasil.library_dirs() for installed native library directories.

MPI

The wheel includes a TCP/shared-memory MPICH runtime and Boost.MPI. MPI remains opt-in and is not linked by yggdrasil::yggdrasil:

find_package(yggdrasil CONFIG REQUIRED)
set(MPI_HOME "${YGGDRASIL_NATIVE_PREFIX}")
set(MPI_CXX_SKIP_MPICXX ON)
find_package(MPI REQUIRED COMPONENTS CXX)
find_package(Boost CONFIG REQUIRED COMPONENTS mpi serialization
    PATHS "${YGGDRASIL_NATIVE_PREFIX}" NO_DEFAULT_PATH)
target_link_libraries(distributed PRIVATE
    MPI::MPI_CXX Boost::mpi Boost::serialization)

The launcher is ${YGGDRASIL_NATIVE_PREFIX}/bin/mpiexec, or from Python, pyyggdrasil.native_prefix() / "bin" / "mpiexec". Use the bundled launcher and libraries together; vendor interconnects and vendor MPI require a separate source build.

fmt Formatters

Yggdrasil's public fmt::formatter specializations are guarded by the YGG_ENABLE_FMT_FORMATTERS macro, which defaults to 1 (yggdrasil/core/config.hpp). Consumers can opt out by defining YGG_ENABLE_FMT_FORMATTERS=0. For Yggdrasil's own builds, the YGGDRASIL_ENABLE_FMT_FORMATTERS CMake option (default ON) toggles the macro.