Reyes isn't a global illumination algorithm, in fact it doesn't prescribe any kind of illumination at all. Global illumination was first described by Cindy Goral, Ken Torrance and Donald Greenberg in the constrained setting of diffuse reflectance in polygonal scenes; the first general GI algorithm, path tracing, was introduced in 1986 by James Kajiya.
https://en.wikipedia.org/wiki/Radiosity_(computer_graphics)