This project has been made at the school 42 with C, OpenCL and OpenGL.
It shows millions of particles moving around.
The particle computation is done on the GPU with OpenCL, and the display is also done on the GPU with OpenGL.
Both API are designed to interoperate, they share the particles data to avoid overheads.
In the following video there is 3 millions particles moving around the cursor at 60 frames per second.