This implementation uses my HLSL-to-ISPC helper library .
ispc is a compiler for a variant of the C programming language, with extensions for "single program, multiple data" (SPMD) programming. Under the SPMD model, the programmer writes a program that generally appears to be a regular serial program, though the execution model is actually that a number of program instances execute in parallel on the hardware. 
To run the sample, simply execute the provided binary. You can also recompile it via hlsl-to-ispc.sln.
 Beason, Kevin. smallpt. http://www.kevinbeason.com/smallpt/
 Barré-Brisebois, Colin. HLSL to ISPC: ispc-hlsl. https://github.com/zigguratvertigo/hlsl-to-ispc