Installation and building¶

Requirements¶

A C++17 compiler (GCC or Clang) with OpenMP support.
CMake ≥ 3.10.
Network access at configure time: the build automatically downloads several dependencies through CMake FetchContent / ExternalProject.

Bundled / fetched dependencies¶

The CMakeLists.txt pulls in the following automatically:

Dependency	Version	Purpose
FastChem	4.0.2	Equilibrium gas-phase chemistry (built as `fastchem_lib`).
LX-MIE	pinned commit	Mie theory for dust absorption/scattering efficiencies.
Eigen	3.4.0 (header-only)	Dense linear algebra for the Henyey structure solver.
toml++	3.4.0 (header-only)	Parsing of the `config.toml` model configuration.
CppAD	20250000.3	Automatic differentiation for the Henyey Jacobian. Built and installed in isolation via `ExternalProject` into `cppad-install/`.

FastChem internally uses Eigen, which leads to an important build constraint:

Warning

Do not add -march=native to the build flags. FastChem’s bundled Eigen breaks (alignment / vectorisation faults) when compiled with it. The Release configuration deliberately uses only -O3 -DNDEBUG -funroll-loops, and -ffast-math is also omitted to keep the radiative-transfer results bit-reproducible. If architecture-specific vectorisation is ever needed, scope it to individual radiative-transfer translation units — never apply it globally where FastChem/Eigen is compiled.

Building¶

The project follows the standard out-of-source CMake workflow:

$ mkdir build
$ cd build
$ cmake ..
$ make -j

The first cmake .. will clone and build FastChem, LX-MIE, Eigen, toml++ and CppAD; subsequent builds reuse them. The executable is written into the source directory as agb_wind (the CMake RUNTIME_OUTPUT_DIRECTORY is set to the source tree, and the runtime RPATH is pointed at cppad-install/lib so the loader finds libcppad_lib.so).

The default and only configured build type is Release.

Self-test¶

A built-in self-test validates the Henyey structure solver’s automatic- differentiation Jacobian and Newton/eigenvalue machinery without needing a full model:

$ ./agb_wind --selftest

This checks the analytic (CppAD) Jacobian against central finite differences for the Φ equation, the coupled Φ``+dust-moment system and the mass-loss eigenvalue row, runs a transonic eigenvalue solve, and exercises the grey (Lucy) bootstrap. It exits ``0 on success.

Running a model¶

Pass the path to a model folder (containing a config.toml) as the single command-line argument:

$ ./agb_wind IRC10216/

See Running a model for the directory layout and Configuration (config.toml) for the full configuration reference.