论文标题
爱丽丝运行3个在线 /离线处理
The ALICE Run 3 Online / Offline Processing
论文作者
论文摘要
Alice实验已经进行了LHC运行3的重大升级，并将以相互作用速度收集数据比以前大50倍。运行3的新计算方案将传统的在线和离线框架替换为统一的框架，称为O2。处理将分为两个阶段。在数据获取过程中，同步处理阶段对在线计算农场进行数据压缩，校准和质量控制。输出存储在现场磁盘缓冲区上。当LHC中没有光束时，使用相同的计算农场用于数据产生最终重建输出的数据的异步。 O2项目由三个主要部分组成：。配备GPU的事件处理节点（EPN）提供了大部分计算能力，并执行重建的大部分和校准。第一级处理器（FLP）通过检测器的光学链接接收数据，并在需要的地方执行本地处理，这可以在基于FPGA的读取卡的用户逻辑中可选。在FLP和EPN农场之间，数据分布在网络中，以使EPN接收到处理的完整碰撞数据。物理和数据处理（PDP）组开发了软件框架以及重建和校准算法。当前的O2设置能够实时处理PB-PB碰撞数据以50 kHz相互作用速率的数据获取的峰值数据速率。
The ALICE experiment has undergone a major upgrade for LHC Run 3 and will collect data at an interaction rate 50 times larger than before. The new computing scheme for Run 3 replaces the traditionally separate online and offline frameworks by a unified one, which is called O2. Processing will happen in two phases. During data taking, a synchronous processing phase performs data compression, calibration, and quality control on the online computing farm. The output is stored on an onsite disk buffer. When there is no beam in the LHC, the same computing farm is used for the asynchronous reprocessing of the data which yields the final reconstruction output. The O2 project consists of three main parts:. The Event Processing Nodes (EPN) equipped with GPUs deliver the bulk of the computing capacity and perform the majority of the reconstruction and the calibration. The First Level Processors (FLP) receive the data via optical links from the detectors and perform local processing where it is needed, which can optionally happen in the user logic of the FPGA based readout card. Between the FLP and the EPN farms the data is distributed in the network such that the EPNs receive complete collision data for the processing. The Physics and Data Processing (PDP) group develops the software framework and the reconstruction and calibration algorithms. The current O2 setup is capable of handling in real time the peak data rate foreseen for data taking of Pb--Pb collisions at 50 kHz interaction rate..
