Kokkos

Part 1 Prepare Octo-Tiger for Kokkos:

• Adapt toolchain (use spack)
• Adapt Octotiger to compile with Kokkos (split main file, host-only blacklist, patch nvcc_wrapper, ...)
• Remodel GPU kernel buffer management (create memory pools for arbitrary host/gpu/kokkos data - avoid device malloc)
• Remodel GPU execution management (go from thread_local cuda_streams to executor pools - avoid stream creations)
• Adapt CPU/GPU launch inteface for the pools
• Remove Vc from headers

Part 2 Port Gravity Module to Kokkos

• Remove all thread_local workarounds in the gravity module
• Adapt current CUDA implementation to work with the memory and executor pools (keeps those working with the rest)
• Remove old CUDA management
• Create Kokkos Kernel for the Monopole Interactions
• Adapt Mikaels Kokkos executors and create unified interface for launching Kokkos Kernels on the CPU and GPU (~ 1 week including cleanup)
• Create Kokkos Kernel for the Multipole Interactions (~ 1-2 weeks)
• Evaluate Kokkos vs Cuda performance (Concern: Needless fencing in Kokkos) - In Progress
• Bonus: Test on AMD - In Progress
• Merge master into kokkos branch

Part 3 Port flux method

• Refactor flux scalar single core
• Refactor flux to use explicit SIMD
• Make datastructure more GPU-friendly
• Create first GPU (CUDA?) kernel
• Integrate GPU kernel into existing launch infrastructure

Part 4 Port Reconstruct method

• Switch datastructure over to the flux-way of doing things
• Refactor reconstruct to more easily use the available parallelism (at least 2 weeks given my experience trying to port the last reconstruct, better to plan for extra time)
• Create Basic reconstruct GPU kernel
• Interface reconstruct kernel with the existing GPU Infracstructure (see part 2)
• Evaluate need for optimizations