X-ray scattering experiments using Free Electron Lasers (XFELs) are a powerful tool to determine the molecular structure and function of unknown samples (such as COVID-19 viral proteins). XFEL experiments are a challenge to computing in two ways: i) due to the high cost of running XFELs, a fast turnaround time from data acquisition to data analysis is essential to make informed decisions on experimental protocols; ii) data collection rates are growing exponentially, requiring new scalable algorithms. Here we report our experiences analyzing data from two experiments at the Linac Coherent Light Source (LCLS) during September 2020. Raw data were analyzed on NERSC's Cori XC40 system, using the Superfacility paradigm: our workflow automatically moves raw data between LCLS and NERSC, where it is analyzed using the software package CCTBX. We achieved real time data analysis with a turnaround time from data acquisition to full molecular reconstruction in as little as 10 min -- sufficient time for the experiment's operators to make informed decisions. By hosting the data analysis on Cori, and by automating LCLS-NERSC interoperability, we achieved a data analysis rate which matches the data acquisition rate. Completing data analysis with 10 mins is a first for XFEL experiments and an important milestone if we are to keep up with data collection trends.

翻译：采用自由电子激光（XFEL）的X射线散射实验是解析未知样本（如COVID-19病毒蛋白）分子结构与功能的重要手段。XFEL实验对计算提出双重挑战：其一，由于XFEL运行成本高昂，从数据采集到数据分析的快速周转对实验方案的明智决策至关重要；其二，数据采集速率呈指数级增长，亟需新型可扩展算法。本文报告了2020年9月在直线加速器相干光源（LCLS）两次实验中的数据分析经验。原始数据基于超算设施范式在NERSC的Cori XC40系统上完成分析：工作流程自动将原始数据在LCLS与NERSC之间传输，并使用CCTBX软件包进行分析。我们实现了从数据采集到完整分子重建仅需10分钟的实时数据分析——这一速度足以使实验操作人员做出明智决策。通过将数据分析托管于Cori系统并实现LCLS-NERSC互操作自动化，我们达成了与数据采集速率相匹配的分析速度。在10分钟内完成数据分析是XFEL实验领域的首次突破，对于应对数据采集增长趋势具有里程碑意义。