HL-LHC Computing Review: Common Tools and Community Software
HEP Software Foundation, :, Thea Aarrestad, Simone Amoroso, Markus Julian Atkinson, Joshua Bendavid, Tommaso Boccali, Andrea Bocci, Andy Buckley, Matteo Cacciari, Paolo Calafiura, Philippe Canal, Federico Carminati, Taylor Childers, Vitaliano Ciulli, Gloria Corti, Davide Costanzo, Justin Gage Dezoort, Caterina Doglioni, Javier Mauricio Duarte, Agnieszka Dziurda, Peter Elmer, Markus Elsing, V. Daniel Elvira, Giulio Eulisse, Javier Fernandez Menendez, Conor Fitzpatrick, Rikkert Frederix, Stefano Frixione, Krzysztof L Genser, Andrei Gheata, Francesco Giuli, Vladimir V. Gligorov, Hadrien Benjamin Grasland, Heather Gray, Lindsey Gray, Alexander Grohsjean, Christian Gütschow, Stephan Hageboeck, Philip Coleman Harris, Benedikt Hegner, Lukas Heinrich, Burt Holzman, Walter Hopkins, Shih-Chieh Hsu, Stefan Höche, Philip James Ilten, Vladimir Ivantchenko, Chris Jones, Michel Jouvin, Teng Jian Khoo, Ivan Kisel, Kyle Knoepfel, Dmitri Konstantinov, Attila Krasznahorkay, Frank Krauss, Benjamin Edward Krikler, David Lange, Paul Laycock, Qiang Li, Kilian Lieret, Miaoyuan Liu, Vladimir Loncar, Leif Lönnblad, Fabio Maltoni, Michelangelo Mangano, Zachary Louis Marshall, Pere Mato, Olivier Mattelaer, Joshua Angus McFayden, Samuel Meehan, Alaettin Serhan Mete, Ben Morgan, Stephen Mrenna, Servesh Muralidharan, Ben Nachman, Mark S. Neubauer, Tobias Neumann, Jennifer Ngadiuba, Isobel Ojalvo, Kevin Pedro, Maurizio Perini, Danilo Piparo, Jim Pivarski, Simon Plätzer, Witold Pokorski, Adrian Alan Pol, Stefan Prestel, Alberto Ribon, Martin Ritter, Andrea Rizzi, Eduardo Rodrigues, Stefan Roiser, Holger Schulz, Markus Schulz, Marek Schönherr, Elizabeth Sexton-Kennedy, Frank Siegert, Andrzej Siódmok, Graeme A Stewart, Malik Sudhir, Sioni Paris Summers, Savannah Jennifer Thais, Nhan Viet Tran, Andrea Valassi, Marc Verderi, Dorothea Vom Bruch, Gordon T. Watts, Torre Wenaus, Efe Yazgan
Common and community software packages, such as ROOT, Geant4 and event generators have been a key part of the LHC's success so far and continued development and optimisation will be critical in the future. The challenges are driven by an ambitious physics programme, notably the LHC accelerator upgrade to high-luminosity, HL-LHC, and the corresponding detector upgrades of ATLAS and CMS. In this document we address the issues for software that is used in multiple experiments (usually even more widely than ATLAS and CMS) and maintained by teams of developers who are either not linked to a particular experiment or who contribute to common software within the context of their experiment activity. We also give space to general considerations for future software and projects that tackle upcoming challenges, no matter who writes it, which is an area where community convergence on best practice is extremely useful.