atlas-software

name	atlas-software
description	Use when a question involves ATLAS software concepts: Athena framework, event data model, CP algorithms, derivation formats (DAOD), CMake build system, CVMFS software releases, analysis releases, ASG tools, or any ATLAS-internal software infrastructure. This skill routes to the right resource or subagent; for deep lookup delegate to atlas-docs-expert.

ATLAS Software Orientation

Overview

This skill is a routing map for ATLAS software questions. For any topic below, the authoritative source is the hosted documentation at https://atlas-software.docs.cern.ch/. For deep questions, delegate to the atlas-docs-expert subagent which searches the docs and fetches current content.

When to Use

• Questions about the Athena framework, event data model (xAOD), or CP algorithms
• Navigating derivation formats (DAOD_PHYS, DAOD_PHYSLITE) and their differences
• Setting up or understanding CMake builds for ATLAS packages
• Choosing an analysis release (AnalysisBase vs AthAnalysis) or CVMFS setup
• Any question about ATLAS-internal software infrastructure or ASG tools

Key Concepts

Athena Framework

The C++ event processing framework underlying all ATLAS reconstruction and analysis.

• Framework basics: https://atlas-software.docs.cern.ch/athena/basics/intro/
• Writing algorithms and tools: https://atlas-software.docs.cern.ch/athena/developers/tutorial/writing-algstools/

Event Data Model (EDM)

How physics objects are stored in xAOD files.

• xAOD EDM overview: https://atlas-software.docs.cern.ch/athena/io/
• Container types (xAOD::JetContainer, xAOD::ElectronContainer, etc.)
• Auxiliary stores and decorations (SG::AuxElement::Decorator<T>)
• Reading with SG::ReadHandle<T> and SG::WriteHandle<T>

CP Algorithms (Combined Performance)

Recommended tools for object calibration, scale factors, and systematic uncertainties.

• CP algorithm overview: https://atlas-software.docs.cern.ch/analysis/cp_algs/
• Each physics object has a group-recommended WP and tool:

Object	CP tool interface	Recommended WP
Jets	IJetCalibrationTool, IJetUncertaintiesTool	AntiKt4EMPFlow
Electrons	IEgammaCalibrationAndSmearingTool	TightLH + gradient iso
Muons	IMuonCalibrationAndSmearingTool	Medium + FCLoose iso
b-jets	IBTaggingEfficiencyTool	DL1dv01 77%
MET	IMETMaker	Tight/Loose
Taus	ITauSmearingTool	Medium

Derivation Formats (DAOD)

Slimmed xAOD files produced by the ATLAS derivation framework.

• Derivation framework: https://atlas-software.docs.cern.ch/analysis/analysis_tutorial/AnalysisSWTutorial/derivation_framework/
• DAOD_PHYSLITE: primary analysis format — smaller, CP-recommended variables pre-applied
• DAOD_PHYS: full DAOD — use when PHYSLITE lacks required variables
• Specialized: DAOD_BPHY (B-physics), DAOD_EGAM (egamma), DAOD_JETM (jets), HIGG* (Higgs)
• Check available variables: checkxAOD.py file.pool.root

ASG Tools (Analysis Software Group)

Dual-use tools that work both in Athena and standalone.

• CP algorithms intro (where ASG tools are configured): https://atlas-software.docs.cern.ch/analysis/cp_algs/
• AsgTool base class — lighter than Gaudi tools, works in AnalysisBase
• Property system: declareProperty("Name", m_prop = default, "Description")

CMake Build System

• Package structure: https://atlas-software.docs.cern.ch/athena/developers/cmake/
• atlas_subdir(PackageName) declares the package (single argument)
• Dependencies are declared via LINK_LIBRARIES on atlas_add_library / atlas_add_component etc. (atlas_depends_on_subdirs is obsolete — do not use)
• Build everything: cmake ../source && make (or use acmSetup/acm)
• Build a subset: copy Projects/WorkDir/package_filters.txt, edit it (+/- path regexps), and configure with cmake -DATLAS_PACKAGE_FILTER_FILE=../source/package_filters.txt ../source

CVMFS and Software Releases

• Software at: /cvmfs/atlas.cern.ch/repo/sw/software/
• Setup: asetup AthAnalysis,25.2.X or asetup AnalysisBase,25.2.X
• Run 3 analysis recommendation: AnalysisBase 25.2.X for standalone analysis
• Run 2 legacy: AthAnalysis 22.2.X for Athena-based analysis
• Releases and nightly builds: https://atlas-software.docs.cern.ch/athena/developers/releases/

Analysis Releases (for non-Athena Python workflows)

• TopCPToolkit: wraps CP algorithms for NTuple production → atlas:topcptoolkit
• FastFrames: RDataFrame-based → atlas:fastframes
• coffea + uproot: no Athena dependency → atlas:coffea, atlas:uproot

Canonical Patterns

For any topic above, delegate to the atlas-docs-expert subagent:

• It searches the local docs mirror to locate the relevant page
• Fetches current content from the hosted site
• Provides specific code examples from the official docs

Common routing table:

Question type	Start here
"How do I set up a CP tool in Athena?"	atlas-docs-expert
"What object collection name do I use in PHYSLITE?"	atlas-docs-expert
"How do I build my ATLAS package?"	atlas-docs-expert
"What framework for my analysis?"	atlas:topcptoolkit, atlas:fastframes, atlas:coffea
"How do I find my dataset?"	atlas-data-explorer
"How do I fit my workspace?"	atlas-stats-expert

Gotchas

• All ATLAS energy/momentum values are in MeV: branches like jet_pt, met_met use MeV — divide by 1000 for GeV-scale comparisons.
• PHYSLITE vs PHYS collection names differ: AnalysisJets (PHYSLITE) vs AntiKt4EMPFlowJets (PHYS) — match your config to the input DAOD type.

Interop

• atlas-docs-expert: subagent for deep documentation lookup — use for any specific API, class, or configuration question
• atlas:topcptoolkit, atlas:fastframes, atlas:coffea: downstream analysis framework skills
• atlas-data-explorer: for finding datasets via Rucio/AMI

Docs

https://atlas-software.docs.cern.ch/