I felt the previous comparison left a little to be desired so I have repeated the experiment on 8 cores using the original Haskell code and giving results for 9, 12 and 13 levels of spheres: http://flyingfrogblog.blogspot.com/2010/01/naive-parallelization-c-vs-haskel... -- Dr Jon Harrop, Flying Frog Consultancy Ltd. http://www.ffconsultancy.com/?e