What you were doing when the issue happened?
When I open Alfred Preferences and navigate the tabs at the top, the GPU often switches from integrated to discrete. I can often replicate this e.g. by switching to the appearance tab and selecting another theme.
Whether you were able to replicate it a second time by performing the same action
Yes, see above.
Include any screenshots that might help us
I'm using gfxCardStatus to get notifications when the GPU changes.
Include the Alfred version & build number you are using
3.0.2, Build 676, Tuesday 14th June 2016
Include your OS X version
10.11.5 on a MacBook Pro (Retina, 15-inch, Late 2013)