Why Opencv GPU code is slower than CPU?

Question

I\'m using opencv242 + VS2010 by a notebook.
I tried to do some simple test of the GPU block in OpenCV, but it showed the GPU is 100 times slower than CPU codes. In this

Answer 1

cvtColor isn't doing very much work, to make grey all you have to is average three numbers.

The cvColor code on the CPU is using SSE2 instructions to process upto 8 pixels at once and if you have TBB it's using all the cores/hyperthreads, the CPU is running at 10x the clock speed of the GPU and finally you don't have to copy data onto the GPU and back.