When I open the game in 0.15.2, the framerate is very low, but the problem isn't low ups. I know this because I have a dual screen setup. When I'm typing this, the Chrome-windows is active, and Factorio is running at 60fps on my other monitor. When I go back to the game, it slows down to 20fps. Screenshots:

In the above picture, Chrome is active.

In this picture, the game is active. Why is the fps so low? It was way better in 0.14.