If you have a suspected GPU problem review this: [http://www.apple.com/support/macbookpro-videoissues/|MacBook Pro Repair Extension Program for Video Issues]
Here's an excerpt from Apple's page:
Apple has determined that a small percentage of MacBook Pro systems may exhibit distorted video, no video, or unexpected system restarts. These MacBook Pro systems were sold between February 2011 and December 2013.
Apple or an Apple Authorized Service Provider will repair affected MacBook Pro systems, free of charge. See below for details on affected models and service options.
As of February 20, 2015, the repair process will be available in the U.S. and Canada. In other countries, it will be available as of February 27, 2015.
Symptoms:
An affected MacBook Pro may display one or more of the following symptoms:
Distorted or scrambled video on the computer screen
No video on the computer screen (or external display) even though the computer is on
Computer restarts unexpectedly
Products affected:
* 15-inch and 17-inch MacBook Pro models manufactured in 2011
* 15-inch MacBook Pro with Retina models manufactured from Mid 2012 to Early 2013