The ALICE High Level Trigger: status and plans

21st International Conference on Computing in High Energy and Nuclear Physics

物理学;计算机科学

Krzewicki, Mikolaj^1 ; Rohr, David^1 ; Gorbunov, Sergey^1 ; Breitner, Timo^1 ; Lehrbach, Johannes^1 ; Lindenstruth, Volker^1 ; Berzano, Dario^1

Frankfurt Institute for Advanced Studies, Ruth-Moufang-Str. 1, Frankfurt

60438, Germany^1

关键词: Asynchronous processing;    Detector calibration;    General purpose graphic processing units;    High-level triggers;    Kalman filter algorithms;    On-line calibration;    Online reconstruction;    Realtime data compression;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/664/8/082023/pdf
DOI  :  10.1088/1742-6596/664/8/082023

学科分类：计算机科学（综合）

来源: IOP

【 摘 要 】

The ALICE High Level Trigger (HLT) is an online reconstruction, triggering and data compression system used in the ALICE experiment at CERN. Unique among the LHC experiments, it extensively uses modern coprocessor technologies like general purpose graphic processing units (GPGPU) and field programmable gate arrays (FPGA) in the data flow. Realtime data compression is performed using a cluster finder algorithm implemented on FPGA boards. These data, instead of raw clusters, are used in the subsequent processing and storage, resulting in a compression factor of around 4. Track finding is performed using a cellular automaton and a Kalman filter algorithm on GPGPU hardware, where both CUDA and OpenCL technologies can be used interchangeably. The ALICE upgrade requires further development of online concepts to include detector calibration and stronger data compression. The current HLT farm will be used as a test bed for online calibration and both synchronous and asynchronous processing frameworks already before the upgrade, during Run 2. For opportunistic use as a Grid computing site during periods of inactivity of the experiment a virtualisation based setup is deployed.