Maintenance Madness: Fermi LAT Offline Computing's Experience with External Libraries and Support of its User and Developer Communities

Kelly, Heather

The Fermi Observatory, including the Large Area Telescope (LAT), was launched June 11, 2008. The LATís offline software includes a detailed C++ Monte Carlo simulation utilizing Geant4, event by event reconstruction with ROOT output for use within the collaboration, and science tools utilizing FITS which are ultimately distributed to the user community. Within the LAT team, we support Redhat Linux, Windows, and are moving toward Mac OS as well. We support the full use of Visual Studio as a development environment, while we use one build tool for our automated builds across all operating systems. We continue to rely upon a number of external libraries including: ROOT, Gaudi, Swig, and Xerces. With eight years ahead of us, we are in the phase of our project where we must move forward to support modern operating systems and compilers to get us through the life of the mission. This means upgrading our external libraries as well. Meanwhile, it is crucial to our production system that we carefully orchestrate all upgrades to insure stability. There have been a number of lessons learned, with undoubtedly more to come. This poster will focus on our experiences with our external libraries, maintenance of a large scale offline software project, and support of our development community.

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