How to keep Matlab going on a long calculation?

I run simulations, some of which take on the order of 90 minutes. If I get one started and walk away to do other things, I find upon returning that the screen is dark and computation has stopped after 30 minutes or so. If I then click on the mouse and get the screen to come back, the simulation continues. I am using Windows 7 Professional on an HP laptop with an Intel I7 processor and 16 Gigs of memory. Is there a way to keep the computer running when I am not present? I am using R2015b. Thanks.

[Stephen23]

Most likely this has nothing to do with MATLAB. Change your power settings:

http://www.makeuseof.com/tag/windows-7-power-options-sleep-modes-explained/

Answer 1

[KSSV]

Dear David Koenig... I don't think you have to change any settings in MATLAB. Your computer is going to sleep...check power options and change the sleep setting there.....

[Noah Stam]

I come across similar problem (only my calculations take in the order of 10 hours). I made sure my pc wouldn't update overnight and that my pc wouldn't go to sleep. This morning I woke up and the matlab window as gone...