How to switch to the built-in Intel video card to leave the working Nvidia one for working with CUDA?

Question

linux

Laptop lenovo z 580, OS ubuntu gnome 15.10, video card GeForce GT 640M (with optimus technology) and the second - built-in Intel.
By hook or by crook, I got optimus support for myself with switching between cards in nvidia-settings without bumblebee, through Nvidia Prime. However, I began to use CUDA for calculations, and when it counts the entire system, it slows down because the counting card is still occupied by the screen.
I wanted to find a way to turn on the Intel card and count on the Nvidia card that is not used by the screen at that time, but when switching through nvidia-settings, the card that is not used by the screen, as I understand it, is completely cut down.
The question is - how to switch to the Intel brief to leave the working Nvidia for use where?

Answer 1

https://wiki.ubuntu.com/Bumblebee