Rapid event extraction and tensorial event adaption: Libraries for efficient access and generic reweighting of parton-level events and their implementation in the MadtRex module

We present and , C++17 libraries for efficient management of parton-level hard scattering event information and completely generic reweighting of such events, respectively. is primarily an interfacing and I/O library for Les Houches Event format files and provides an internal event format designed with data parallelism in mind, and extends this format to provide full parton-level reweighting functionality with minimal code needing to be written by the end user. These libraries serve as the foundation for the MadtRex reweighting module for MadGraph5_aMC@NLO , extending the functionality of the plugin to allow for data-parallel model-generic leading order parameter reweighting with on-CPU hardware acceleration and GPU offloading, speeding up reweighting by more than two orders of magnitude compared to MadGraph5_aMC@NLO running on the exact same hardware while providing trivial scalability to larger and distributed systems.