ESS Data Reduction Monorepo

Monorepo for ESS neutron scattering data reduction packages, managed with pixi.

Package	Description
essreduce	Common data reduction tools (core)
essdiffraction	Diffraction data reduction for the European Spallation Source
essimaging	Neutron imaging (ODIN, TBL, YMIR)
essnmx	Data reduction for NMX at the European Spallation Source.
essreflectometry	Reflectometry data reduction for the European Spallation Source
esssans	Data reduction for SANS at the European Spallation Source.
essspectroscopy	Data reduction for SANS at the European Spallation Source.

Dependency graph

essreduce
├── essdiffraction
├── essimaging
├── essnmx
├── essreflectometry
└── esssans
└── essspectroscopy

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Developer Guide

Prerequisites

Install pixi:

curl -fsSL https://pixi.sh/install.sh | bash

Setup

git clone git@github.com:scipp/ess.git
cd ess

# Install all packages (editable, with test deps):
pixi install

# Or just one package:
pixi install -e essreduce

The pixi.lock file pins all dependencies reproducibly. No tox, no pip-compile, no manual virtualenv.

Running tests

# Test a package:
pixi run test essreduce
pixi run test essimaging
pixi run test essreflectometry
pixi run test essdiffraction
pixi run test essnmx
pixi run test esssans
pixi run test essspectroscopy

# Test a single file:
pixi run -e essreduce pytest packages/essreduce/tests/normalization_test.py

Linting and formatting

pixi run -e lint lint       # all pre-commit hooks
pixi run -e lint check      # ruff check
pixi run -e lint format     # ruff format

Building docs

pixi run docs-essreduce
pixi run docs-essimaging
pixi run docs-essreflectometry
pixi run docs-essdiffraction
pixi run docs-essnmx
pixi run docs-esssans
pixi run docs-essspectroscopy

Adding or changing dependencies

Edit the package's pyproject.toml, then re-lock:

pixi install

Commit the updated pixi.lock.

Releasing a package

Push a tag with the package prefix:

git tag essreduce/26.3.0
git push origin main --tags

The release.yml workflow builds, publishes to PyPI, and deploys docs.

How CI works

• On PRs: Only changed packages are tested (changing essreduce also tests essimaging)
• Nightly: All packages tested against latest deps + lower-bound deps
• Weekly: All packages tested on macOS and Windows

Repo structure

pixi.toml                   ← workspace root (features, tasks, environments)
pixi.lock                   ← single lockfile for all packages
.pre-commit-config.yaml     ← shared linting hooks
packages/
  essdiffraction/
    pyproject.toml
    src/ess/
      diffraction/          ← source code (ess.diffraction namespace)
      dream/                ← source code (ess.dream namespace)
      ...
    tests/
    docs/
  essimaging/
    pyproject.toml
    src/ess/
      imaging/              ← source code (ess.imaging namespace)
      odin/                 ← source code (ess.odin namespace)
      ...
    ...
  essnmx/
    pyproject.toml
    src/ess/nmx/            ← source code (ess.nmx namespace)
    ...
  essreduce/
    pyproject.toml          ← package deps, version, pytest config
    src/ess/reduce/         ← source code (ess.reduce namespace)
    ...
  essreflectometry/
    pyproject.toml
    src/ess/
       reflectometry/       ← source code (ess.reflectometry namespace)
       ...
    ...
  esssans/
    pyproject.toml
    src/ess/
      sans/                 ← source code (ess.sans namespace)
      ...
    ...
  essspectroscopy/
    pyproject.toml
    src/ess/
      spectroscopy          ← source code (ess.spectroscopy namespace)
    ...