Awesome article. This is what I want to see in HN every day, very interesting and relatively unknown CS topic, well explained, easy to understand, well written code. Basically flawless. Unfortunately, HeapSort and its variants aren't that popular any more since they're not cache friendly. To see that, observe that in the article author maintains bunch of heaps in the array and even though it's asymptotically fast and in-place, you'll have to keep referring to distant parts of the array, causing cache misses.