When the kernel is running, the discrete GPU is enabled automatically and battery life plummets, even though my code uses no CUDA or OpenCL functions. Is it possible to prevent that from happening?
Mathematica 10; 2015 15"-screen Retina MacBook Pro
Use the gfxCardStatus utility to force integrated graphics. This must be done while integrated graphics is in use, i.e. before Mathematica is started.
Sometimes it may be necessary to switch twice before the setting sticks. (The gfxCardStatus author is aware and told me that he has no solution.)
Note: If discrete graphics are in use, it is not possible to force switching back to integrated graphics until you quit all programs that are using the discrete card. The reverse is possible, however, I noticed that sometimes Mathematica will crash a few minutes after the switch. It is best to lock the setting before starting Mathematica, and not toggle it until you're done using it.
Mathematica forces discrete graphics since version 9 (not in version 8). Wolfram is aware of the situation as I reported it in 2012.