FairMQ for Online Reconstruction - An example on PANDA test beam data

Abstract

One of the large challenges of future particle physics experiments is the trend to run without a first level hardware trigger. The typical data rates exceed easily hundreds of GBytes/s, which is way too much to be stored permanently for an offline analysis. Therefore a strong data reduction has to be done by selection of only those data, which are physically interesting. This implies that all detector data are read out and have to be processed with the same rate as it is produced. Several different hardware approaches from FPGAs, GPUs to multicore CPUs and mixtures of these systems are under study. Common to all of them is the need to process the data in massive parallel systems.One very convenient way to realize parallel systems on heterogeneous systems is the usage of message queue based multiprocessing. One package that allow development of such application is the FairMQ module in the FairRoot simulation framework developed at GSI. FairRoot is used by several different experiments at and outside the GSI including the $\overline{{\rm{P}}}$ANDA experiment. FairMQ is an abstract layer for message queue base application, it has up to now two implementations: ZeroMQ and nanomsg. For the $\overline{{\rm{P}}}$ANDA experiment, FairMQ is under test in two different ways. On the one hand side for online processing test beam data of prototypes of sub-detectors of $\overline{{\rm{P}}}$ANDA and, in a more generalized way, on time-based simulated data of the complete detector system. The first test on test beam data is presented in this paper