Oh well, this is embarrassing. I rewrote the CPU benchmark in C and it does indeed perform much faster. I think it has something to do with the use of the CUDA

Oh well, this is embarrassing. I rewrote the CPU benchmark in C and it does indeed perform much faster. I think it has something to do with the use of the CUDA complex number functions. Unfortunately, I do not have my desktop with the GPU set up to recompute the GPU numbers.