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Computing Technical Design Report
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Computing Technical Design Report
This Technical Design Report describes the ATLAS Software & Computing Project. The project covers all developments of offline software for the ATLAS experiment, the definition of the computing environment, the provision of hardware and manpower resources, and the operation of the ATLAS offline Computing system.
In particular, the Software & Computing Project is responsible for the provision of the software framework and services, the data management system, user-support services, and the world-wide data access and job-submission system. The development of detector-specific algorithmic code for simulation, calibration, alignment, trigger and reconstruction is under the responsibility of the detector projects, but the Software & Computing Project plans and coordinates these activities across detector boundaries. In particular, a significant effort has been made to ensure that relevant parts of the "offline" framework and event-reconstruction code can be used in the High-Level Trigger. Similarly, close cooperation with Physics Coordination and the Combined Performance groups ensures the smooth development of global event-reconstruction code and of software tools for physics analysis.
The ATLAS Computing Model is described in Chapter 2. The high-level Computing Model defines the requirements on the architecture and performance of the software and of the overall computing system. Chapter 3 describes all software development activities that are part of the Software & Computing Project. The ATLAS Collaboration set up in 2004 an ATLAS-wide Database and Data Management Project, which is responsible for all data management issues, from technical detector construction data to online run configuration and world-wide distribution of event and conditions data; this project is described in Chapter 4.
The needs of large-scale simulation, reconstruction and analysis of ATLAS data require the development of a world-wide distributed computing system, which allows efficient data access and makes use of all available computing resources; the developments towards such a system are described in Chapter 5. Chapter 6 describes the experience we have had so far with large-scale distributed computing operations, in the context of the Data Challenges that were run from 2001 onwards, and the development towards the operation system that will be needed at experiment turn-on. Taking into account the Computing Model and the current, and extrapolated, performance of ATLAS software and other computing tools, Chapter 7 lists the hardware resources that will be required in order to process and analyse ATLAS data. Finally, the organization of the Software & Computing Project is described in Chapter 8, together with a summary of high-level project milestones.
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