Learn about a case-study comparing OpenACC and OpenMP4.5 in the context of stellar explosions. Modeling supernovae requires multi-physics simulation codes to capture hydrodynamics, nuclear burning, gravitational forces, etc. As a nuclear detonation burns through the stellar material, it also increases the temperature. An equation of state (EOS) is then required to determine, say, the new pressure associated with this temperature increase. In fact, an EOS is needed after the thermodynamic conditions are changed by any physics routines. This means it is called many times throughout a simulation, requiring the need for a fast EOS implementation. Fortunately, these calculations can be performed independently during each time step, so the work can be offloaded to GPUs. Using the IBM/NVIDIA early test system (precursor to the upcoming Summit supercomputer) at Oak Ridge National Laboratory, we use a hybrid MPI+OpenMP (traditional CPU threads) driver program to offload work to GPUs. We'll compare the performance results as well as some of the currently available features of OpenACC and OpenMP4.5.