astronereus

Python frontend for Nereus — trans-dimensional Bayesian inference for exoplanet orbits.

You do not need Julia. Nereus itself is Julia, but this package fetches a prebuilt runtime on first use and runs it out-of-process in a warm daemon. Nothing is compiled at install time.

pip install astronereus

That is the whole install. The first time you actually ask for a fit, the runtime (~480 MB) is fetched and warmed once, and you are told it is happening:

astronereus: no Julia runtime yet -- fetching it once now.
astronereus: fetching runtime (macos-arm64, julia 1.11.9) ...
astronereus: unpacking ...
astronereus: warming the runtime (one-time, a few minutes) ...
astronereus: ready (207s)

pip cannot do that step itself -- wheels have no post-install hook -- so it happens on first use instead. To get it over with ahead of a workshop or a flight, run it deliberately:

python -c "import astronereus; astronereus.install()"

NEREUS_NO_AUTO_INSTALL=1 turns the automatic fetch off and makes the first call fail with instructions instead, for CI and air-gapped machines.

The distribution and the import are both astronereus. The name nereus on PyPI belongs to an unrelated geophysics package, and a distribution whose import name differs from its install name is a thing every user has to be told, so they are deliberately the same string here.

Use

import astronereus

summary = astronereus.run_job(cfg)          # one-shot

with astronereus.session() as s:            # or reuse one warm daemon
    a  = s.run_job(cfg_a)
    pg = s.detect.rv_periodogram(t=t, rv=rv, rv_err=err)

Typed entry points per observable — fit_rv, fit_transit, fit_astrometry, fit_rm, fit_tomography, fit_ttv, fit_binary, fit_joint — take channel objects (RV, Transit, Astrometry, RM, Night, TTV, SB2) and return a JobResult.

The first install() unpacks the runtime and warms it once (a few minutes); every process after that starts in about twenty seconds. NEREUS_BUNDLE_URL points the installer at a local file or file:// URL — that is the intended path for a workshop room, where thirty people pulling half a gigabyte over conference wifi is not a plan.

Runtime bundles

Prebuilt runtimes are attached to the Nereus.jl releases, with SHA256SUMS alongside:

install() picks the one for your platform and verifies it against the published checksum.

Upgrading the package does not refresh a runtime you already have — the bundle is a separate download cached outside site-packages. When a release ships against a newer Nereus, session() says so on start-up; get it with:

python -c "import astronereus; astronereus.install(force=True)"
``` For a classroom, fetch it once and point everyone at the
local copy instead:

```sh
export NEREUS_BUNDLE_URL=/Volumes/NEREUS/nereus-runtime-1.11.9-macos-arm64.tar.zst

NEREUS_HOME relocates the runtime cache out of the default platform cache directory.

Licence

MIT — see LICENSE.