Well, GPUs expose the memory hierarchy to the programmer and have atrocious latency when hitting global memory with unordered memory access patterns. Your only

Well, GPUs expose the memory hierarchy to the programmer and have atrocious latency when hitting global memory with unordered memory access patterns. Your only chance to make a GPU outperform a CPU is to design your algorithm completely around memory usage. The difference between doing it right and wrong can be several orders of magnitude. Even CPUs show huge performance gains when all the algorithm's data fits in the cache. This can easily be a factor 10 or more when you get it right.