Software for the LHCb experiment

LHCb is an experiment for precision measurements of CP-violation and rare decays in B mesons at the LHC collider at CERN. The LHCb software development strategy follows an architecture-centric approach as a way of creating a resilient software framework that can withstand changes in requirements and technology over the expected long lifetime of the experiment. The software architecture, called GAUDI, supports event data processing applications that run in different processing environments ranging from the real-time high-level triggers in the online system to the final physics analysis performed by more than 100 physicists. The major architectural design choices and the arguments that lead to these choices will be outlined. Object oriented technologies have been used throughout. Initially developed for the LHCb experiment, GAUDI has been adopted and extended by other experiments. Several iterations of the GAUDI software framework have been released and are now being used routinely by the physicists of the LHCb collaboration to facilitate their development of data selection algorithms. The LHCb reconstruction (Brunel), the digitization (Boole) and analysis (DaVinci) applications together with the simulation application (Gauss), also based on Geant4, and event and detector visualization program (Panoramix) are all based on the GAUDI framework. All these applications are now in production.