Have to reset the SMC on Retina Macbook Pro very often
Instead of resenting the SMC (a painful procedure) try this free software.

gfxCardStatus 
It is an unobtrusive menu bar app for OS X that allows MacBook Pro users to see which apps are affecting their battery life by using the more power-hungry graphics and

Manually switch to Integrated Only or Discrete Only mode to force one GPU on or the other.

Since I am not sure of your model year, it works on:

OS X Lion (10.7) or newer
2008-2012, 15-17" dual-GPU MacBook Pro