primat

primat is a precise Big Bang Nucleosynthesis (BBN) solver, distributed as a single pip-installable package with two interchangeable backends: a fast C engine (the default) and a pure-Python implementation used as a fallback and for development. It integrates the coupled ODEs of the cosmological background (photon/neutrino temperatures, scale factor) together with a nuclear reaction network to predict the primordial abundances of H, D, ³He, ⁴He, ⁷Li and heavier nuclides.

Quick start

pip install primat

from primat.backend import run_bbn

result = run_bbn({"Omegabh2": 0.02242})

print(f"YP  (BBN) = {result['YPBBN']:.8f}")  # 0.24699911
print(f"D/H       = {result['DoH']:.7e}")    # 2.4350167e-05

run_bbn() is the main entry point and automatically selects the best available backend (fast C engine by default, pure-Python fallback if needed). Pass an optional parameter dict to override defaults; all keys are optional and drawn from primat/config.py’s DEFAULT_PARAMS.

Four ways to use primat

All four produce identical results (to the cross-backend tolerance described in primat.backend — backend dispatch).

  1. Python API (recommended) — primat.backend.run_bbn(params), shown above. Force a specific backend with force_backend="c" / force_backend="python".

  2. Command-line interface:

    primat --Omegabh2 0.02242 --network large --amax 8

    See Command-line interface for the full flag reference (auto-generated from primat --help); anything not exposed as a flag is reachable via the repeatable --set KEY=VALUE escape hatch.

  3. Graphical interface — after pip install "primat[gui]", run primat-gui for a browser-based parameter form, interactive abundance-evolution plot, and final-abundances panel. Supports custom networks (see Custom networks (GUI zip and API)) and either backend.

  4. Example scripts (development/source-only) — python runfiles/primat_run.py, primat_compare.py, primat_reference_run.py, primat_mc.py; run from a source checkout’s repo root.

Citing primat

If you use primat in published work, please cite:

Pitrou, Coc, Uzan, Vangioni, Physics Reports 04 (2018) 005 (arXiv:1801.08023).

See Citing primat for the BibTeX entry.