Speaker
Description
ALICE is the dedicated heavy ion experiment at the LHC at CERN recording lead-lead collisions at a rate of up to 50 kHz interaction rate.
ALICE was the first LHC experiment to leverage GPUs for online data processing in LHC Runs 1 and 2, and its Run 3 online data processing scheme today is 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 is conducting an ongoing effort to offload more offline compute steps to GPUs, and to use the GPUs at other GRID sites besides the ALICE online computing farm for offline reconstruction.
The talk will give an overview of the current status and the commissioning of GPUs for offline processing and outline the future plans.
This includes in particular running GRID jobs on the NVIDIA GPUs of the NERSC Perlmutter cluster, which is the first time an LHC experiment uses GRID GPUS for offline reconstruction.
The performance as well as GPU, CPU and memory utilization will be shown when offloading more steps than only TPC tracking to GPU, in particular ITS GPU tracking.