Starting with Upgrade 1 in 2021, LHCb will move to a purely software-based trigger system. Therefore, the new trigger strategy is to process events at the full rate of 30MHz. Given that the increase of CPU performance has slowed down in recent years, the predicted performance of the software trigger currently falls short of the necessary 30MHz throughput. To cope with this shortfall, LHCb's real-time reconstruction will have to be sped up significantly.
We aim to help solve this shortfall by speeding up the track reconstruction of the Vertex Locator which currently takes up roughly a third of the time spent in the first phase of the High Level Trigger. In order to obtain the needed speedup, profiling and technical optimizations are explored as well as new algorithmic approaches. For instance, a clustering based algorithm can reduce the event rate prior to the track reconstruction by separating hits into two sets - hits from particles originating from the proton-proton interaction point, and those from secondary particles - allowing the reconstruction to treat them separately.
We present an overview of our latest efforts in solving this problem, which is crucial to the success of the LHCb upgrade.