How to use Purdue AF¶

User interfaces¶

Purdue AF provides several user interfaces for analysis development:

• JupyterLab — interactive web interface for notebooks, terminals, file browsing, and more. This is the default interface when starting a session.
• Web-based Visual Studio Code (code-server) — to open it, either select the VSCode interface when creating a session, or click "Open VSCode" button at top right of the JupyterLab interface.
• Connection from local VSCode-based IDEs (VSCode, Cursor, etc.)
• SSH connection from a local terminal
• Agentic interface (MCP server) — manage your AF session and Dask clusters from any MCP-capable AI agent (Claude Code, Codex, Cursor, etc.)

Python code development¶

JupyterLab is especially well suited for developing analysis workflows in Python.

• Jupyter Notebooks allow you to write analysis code as a sequence of code and text cells, which can be executed in arbitrary order. In many cases, a single Jupyter Notebook can accommodate a full analysis from data access to producing final plots.

  Jupyter Notebooks support a wide range of plugins and widgets, which allows for a more interactive experience compared to plain Python scripts.

• To execute the code in a Jupyter Notebook, you always need to specify a kernel. At Purdue AF, Jupyter kernels are derived from Pixi or Conda environments — read more in Software stacks.

• We provide a curated "global" Pixi environment, which should work for most applications, unless your code relies on a very specific package version.
• Analysis code written in Python can be accelerated via parallelization. We recommend using Dask for parallelization and distributed computing. For scaling out to multiple computing nodes, use Dask Gateway.

ROOT¶

ROOT is a software package developed by CERN and widely used in high energy physics for histogramming, fitting, and statistical analysis.

• The ROOT console can be launched from a terminal by typing root -l. Note that it is not possible to display canvases or open TBrowser, since the JupyterLab interface does not support X11 forwarding.

• Alternatively, you can turn a Jupyter Notebook into a ROOT console by selecting the ROOT C++ kernel. Similarly to Python notebooks, you can add text cells and execute cells in arbitrary order.

  When working from a Jupyter Notebook, you can display ROOT plots using the TCanvas::Draw method. See an example of a ROOT C++ notebook here.

• The pre-installed ROOT C++ kernel supports the CUDA backend for RooFit. To use it, pass the RooFit::EvalBackend("cuda") argument to model.fitTo() — see Accelerating RooFit with GPUs.

• In Python, ROOT functionality is accessible via the PyROOT package, available in the global environment.

HEP analysis frameworks¶

We aim to support a wide range of modern HEP analysis tools. Below are a few examples of frameworks which have been shown to perform well at Purdue AF:

• Coffea is a popular Python package for efficient columnar particle physics analyses. Coffea implements all common tools used in modern HEP analyses, and has a large and active support community.

  The latest version of Coffea is pre-installed in the global Pixi environment at /work/pixi/global/.

• PocketCoffea is a slim declarative framework built on top of Coffea. It allows you to define an analysis with a few configuration files. A PocketCoffea analysis can be executed in a distributed way using the dask@purdue-af executor, which is based on Dask Gateway.

• RDataFrame is another common HEP analysis framework based on ROOT. An RDataFrame analysis can be written in either C++ or Python. Purdue AF supports RDataFrame in any Pixi or Conda environment where ROOT is installed.

Scaling out¶

When your analysis outgrows the resources of a single session, several options are available — see Scaling out for a detailed comparison:

• Dask — parallelize any Python code over local cores, or scale out to hundreds of cores via Dask Gateway (available to all users).
• Slurm — batch submission to Purdue computing clusters (Purdue users only).
• CRAB — submission of CMSSW jobs to the Worldwide LHC Computing Grid.

GPUs¶

At Purdue AF, you can start a session with a GPU by selecting it at the resource selection step. We have a limited number of Nvidia A100 GPUs, available in two configurations:

See GPU access at Purdue AF for more details.