Thanks for sharing this. Especially on the page there is a presentation as well as several ports of this same program to other languages like OCaml, Haskell and JavaScript. Interesting to see that the OCaml version is on par with the C++ version performance wise, but is 47% shorter. However the Haskell version is not shorter and 4.5 times slower?

And here's a comparison between that (smallpt) and the equivalent (smallptGPU) using a GPU:

http://davibu.interfree.it/opencl/smallptgpu/smallptGPU.html

All VERY interesting stuff.

And if you like that (spheres only), you might also like this (general triangles-based), in 444 lines of Scala (and OCaml, Python, Ruby, Lua, Scheme, C++, and C):

http://www.hxa.name/minilight/

All this reminds me of Paul Heckbert's ray tracer written on the back of his business card: http://www.cs.cmu.edu/~ph/src/minray/minray.card.c

Now that is impressive.

Even more interesting!