GPU Optimizations for Atmospheric Chemical Kinetics

We present a series of optimizations to alleviate stack memory overflow issues and improve overall performance of GPU computational kernels in atmospheric chemical kinetics model simulations. We use heap memory in numerical solvers for stiff ODEs, move chemical reaction constants and tracer concentration arrays from stack to global memory, use direct pointer indexing for array memory access, and use CUDA streams to overlap computation with memory transfer to the device. Overall, an order of magnitude reduction in GPU memory requirements is achieved, allowing for simultaneous offloading from multiple MPI processes per node and/or increasing the chemical mechanism complexity.