GPU Offloading of a Large-Scale Gyrokinetic Particle-in-Cell Fortran Code on Summit: From OpenACC to OpenMP. - Qiheng Cai; Junyi Cheng; Yang Chen; Marcus Wagner; Christopher S. Daley; Dossay Oryspayev; Stefan Tirkas; Sophie Redd; Scott E. Parker (WACCPD@SC, 2021)