在GRID上为ALICE第3期离线重建使用GPU
Usage of GPUs for ALICE Run 3 Offline Reconstruction on the GRID
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中文总结 AI 辅助
ALICE在GRID上利用GPU开展第3期离线重建，将更多离线步骤卸载到GPU，提升了29%的吞吐量，还实现了在NERSC集群GPU上的首次LHC离线重建应用。
中文摘要 AI 辅助
ALICE是大型强子对撞机（LHC）中专门的重离子实验，记录的铅-铅（Pb-Pb）碰撞相互作用速率最高达50 kHz。它是LHC第1、2期实验中首个利用GPU进行在线数据处理的实验，其第3期在线数据处理目前完全基于GPU，超过90%的计算负载被卸载到加速器上。为了在LHC停机期间高效利用在线处理服务器农场进行离线处理，ALICE自2023年起已在GPU上运行离线时间投影室（TPC）径迹重建。此后，ALICE持续推进将更多离线重建步骤卸载到GPU的工作，并利用ALICE在线计算农场之外的其他GRID站点的GPU进行离线重建，特别是将径迹模型解码和内部径迹系统（ITS）重建移植到GPU后，吞吐量提升了29%。2026年，ALICE在NERSC Perlmutter集群的NVIDIA GPU上运行了首批GPU重建作业，标志着GRID上首次将GPU用于LHC离线重建。用户只需指定所需的GPU数量和类型即可提交GPU重建作业，底层基础设施会透明处理所有剩余配置。
英文摘要
ALICE, the dedicated heavy ion experiment at the LHC, records Pb-Pb collisions at an interaction rate of up to 50 kHz. It was the first LHC experiment to leverage GPUs for online data processing during LHC Runs 1 and 2, and its Run 3 online data processing is now fully based on GPUs with more than 90% of the compute load offloaded to the accelerator. In order to use its online processing server farm also for offline processing in an efficient way while the LHC is not operating, ALICE has been running the offline TPC tracking on GPUs since 2023. Since then, ALICE has been conducting an ongoing effort to offload more offline reconstruction steps to GPUs, and to use the GPUs at other GRID sites beyond the ALICE online computing farm for offline reconstruction. In particular, porting the track model decoding and ITS tracking to GPU has improved the throughput by 29%. In 2026, ALICE ran the first GPU reconstruction jobs on the NVIDIA GPUs of the NERSC Perlmutter cluster, marking the first use of GPUs for LHC offline reconstruction on the GRID. Users can submit GPU reconstruction jobs by specifying only the required GPU count and type, while the underlying infrastructure handles all remaining configurations transparently.
