how to know if the installation is ok?

Hi so i have install drivers,toolkit and sdk. I can run the sdk program but how to know if the code run on gpu?
Because most of the nvidia example have a very short time execution an most of them use the cpu to compare results. So with a top i can see the use of cpu but not the use of cpu.
It is possible to find a big matrix multiplication for exemple who one code use the gpu and the other in C use the cpu.
Thanks for answer

You might be able to write a short Matrix Multiplication, run it on the CPU, and time it, I think NVIDIA offers a sample Matrix Multiplication that you can also run and time that as well. You should be able to run it faster on the GPU.

You can run deviceQuery or bandwithtest in SDK to verify if your GPU is working.