Allen: A High-Level Trigger on GPUs for LHCb. - Roel Aaij; Johannes Albrecht; M. Belous; Pierre Billoir; Thomas Boettcher; A. Brea Rodriguez; Dorothea Vom Bruch; Daniel Hugo Cámpora Pérez; A. Casais Vidal; Daniel C. Craik; Placido Fernandez Declara; L. Funke; et al. (Comput. Softw. Big Sci., 2020)