Performance Evaluation of a GPU-based Monte Carlo Simulation Package for Water Radiolysis with sub-MeV Electrons

The simulation of water radiolysis including three stages, physical, physico-chemical and chemical, modeling the interactions between water and radicals is essential to understand the radiobiological mechanisms and quantitatively test some hypotheses in related problem. Monte Carlo (MC) simulation is recognized as one of the most accurate approaches for the computations of the water radiolysis process. Geant4-DNA which extending the Geant4 Monte Carlo simulation toolkit provides accurate descriptions of the initial physical process of ionization, along with the pre-chemical production of ion species and subsequent chemistry, in a single application for water radiolysis. To accelerate the long execution time of Geant4-DNA simulation, an open source GPU code for water radiolysis simulation, gMicroMC, has been developed. In this paper, we focus on reviewing the GPU implementation architecture of each stage of gMicroMC and evaluating the computational performance in the sub-MeV range of incident electrons. The experimental results of gMicroMC show up to three orders of magnitude performance gain, up to 1690x, with recent generations of NVIDIA graphic cards compared with Geant4-DNA running on a single CPU thread.