Speaker
Description
FastChain is a key component of ATLAS preparations for Run 4, providing a unified, configurable framework that integrates simulation, reconstruction, and downstream data reduction into a single end-to-end workflow. By eliminating intermediate data formats and enabling tight coupling between workflow stages, FastChain improves resource utilization efficiency and reduces disk I/O.
To improve scalability, the unified FastChain workflow incorporates and benchmarks advanced fast-simulation and reconstruction components, such as Fast Track Simulation (Fatras) and FastCaloSim. Ongoing R&D focuses on improving fast-simulation accuracy and robustness under Run-4 conditions using the Geant4 fast-simulation interface and simplified detector descriptions.
We report on ongoing efforts to integrate FastChain into the ATLAS production system, focused on establishing an optimal single end-to-end processing configuration to replace the traditional multi-step production chain. Current studies focus on benchmarking and characterizing CPU, memory, and I/O usage across both Grid and HPC environments, supported by emerging tools for workflow-level monitoring and performance analysis of the different combinations of fast-simulation and reconstruction techniques.
Together, these developments demonstrate how FastChain serves not only as a workflow consolidation effort but also as a flexible platform for integrating and validating fast-simulation technologies at scale. This approach is expected to play a central role in enabling sustainable and performant ATLAS production workflows for Run 4 and beyond.