I just found an interesting blog about different algorithms for GPU path tracing.
Ray Tracey’s blog
Also the author of this blog (Sam Lapere) have some shared code on GitHub
I’m posting here hoping that will be helpful if somebody want to add some GPU capabilities for Appleseed.
If we were to implement GPU rendering, we might use the NVIDIA Optix ray tracing library instead of reimplementing our own ray tracing code.
That said, we don’t have any immediate plans to pursue GPU rendering.