Lukasstockner97 is experimenting with Light Portals, a technology to help Cycles optimize rendering times by pre-defining areas of environmental lights. It results in faster, less grainy renders.
Today, I tried out to implement light portals in Cycles, and it worked out really cool!
For those who don't know about light portals (like me two days ago ): Essentially, they are guides placed in indoor scenes that help the renderer to "find" environment lighting. For a forward path tracer like Cycles, they are only useful for environment light, not for sunlight (that needs bidirectional transport, as in Lux).
