  In high energy physics (HEP) experiments, the reconstruction of charged
particle trajectories is one of the most fundamental yet computationally
expensive parts of event processing. At future hadron colliders such as the
High-Luminosity Large Hadron Collider (HL-LHC), there can be up to ten thousand
particles per event. This increases the track reconstruction time by a factor
about 5 compared to the current tracking environment. Efficient and fast
tracking software is necessary to maintain and improve the tracking
performance. This can benefit from both fast tracking algorithms and modern
computing architectures with many cores and accelerators.
  The Acts (A Common Tracking Software) project encapsulates the current ATLAS
tracking software into an experiment-independent software designed for modern
computing architectures. It provides a set of high-level track reconstruction
tools agnostic to the details of the detector and magnetic field configuration.
Particular emphasis is placed on thread-safety of the code in order to support
concurrent event processing with context-dependent detector conditions, such as
detector alignments or calibrations. Acts aims in addition to be a research and
development platform for studying innovative tracking techniques and exploiting
modern hardware architectures.
