Thanks for your reply !
It is true that everything is quiet ‘small’ on my context. But still take a lot of time on the CPU so I hoped naively that GPU could help…
Anyway, when I run the program on the CPU, I have a 80% utilization of the CPU and GPU is effectively at 0.
On GPU, CPU is almost at 0 and GPU at 5%.
So my conclusion is that you are right. My small business has nothing to do on the GPU. But still I am wondering why GPU does not help…