[JonChesterfield]

Well, that is what a GPU is. Cuda / openmp etc are attempts at conveniently programming a mixed cpu/gpu system.

If you don't want that, program the GPU directly in assembly or C++ or whatever. A kernel is a thread - program counter, register file, independent execution from the other threads.

There isn't a Linux kernel equivalent sitting between you and the hardware so it's very like bare metal x64 programming, but you could put a kernel abstraction on it if you wanted.

Core isn't very well defined, but if we go with "number of independent program counters live at the same time" it's a few thousand.

X64 cores are vaguely equivalent to GCN compute units, 100 or so if either in a 300W envelope. X64 has two threads and a load of branch prediction / speculation hardware. GCN has 80 threads and swaps between them each cycle. Same sort of idea, different allocation of silicon.