There was a very interesting Omega Tau podcast about this very subject a while back. They go into a lot of detail about the optimization problem and how they address it.

http://traffic.libsyn.com/omegataupodcast/omegatau-146-conta...

Also: a plug for Omega Tau, one of my favorite podcasts. https://omegataupodcast.net

Edited to add: go to the Archive page and scroll down. About half the episodes are in English and half in German.