Allen: A High-Level Trigger on GPUs for LHCb

R. Aaij, J. Albrecht, M. Belous, P. Billoir, T. Boettcher, A. Brea Rodríguez, D. vom Bruch, D. H. Cámpora Pérez, A. Casais Vidal, D. C. Craik, P. Fernandez Declara, L. Funke, V. V. Gligorov, B. Jashal, N. Kazeev, D. Martínez Santos, F. Pisani, D. Pliushchenko, S. Popov, R. QuaglianiM. Rangel, F. Reiss, C. Sánchez Mayordomo, R. Schwemmer, M. Sokoloff, H. Stevens, A. Ustyuzhanin, X. Vilasís Cardona, M. Williams

Research output: Indexed journal article Articlepeer-review

34 Citations (Scopus)


We describe a fully GPU-based implementation of the first level trigger for the upgrade of the LHCb detector, due to start data taking in 2021. We demonstrate that our implementation, named Allen, can process the 40 Tbit/s data rate of the upgraded LHCb detector and perform a wide variety of pattern recognition tasks. These include finding the trajectories of charged particles, finding proton–proton collision points, identifying particles as hadrons or muons, and finding the displaced decay vertices of long-lived particles. We further demonstrate that Allen can be implemented in around 500 scientific or consumer GPU cards, that it is not I/O bound, and can be operated at the full LHC collision rate of 30 MHz. Allen is the first complete high-throughput GPU trigger proposed for a HEP experiment.

Original languageEnglish
Article number7
JournalComputing and Software for Big Science
Issue number1
Publication statusPublished - Dec 2020


  • GPU
  • LHCb
  • Real-time data selection
  • Trigger


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