This is a bit late to add, but from the description of the problem in the article, the way to make the program faster, irregardless of language, is to use a big

This is a bit late to add, but from the description of the problem in the article, the way to make the program faster, irregardless of language, is to use a big array rather than lists and trees. Carve the array up as necessary, so the array of users to offsets in the array where the data is. Basically, be your own memory allocator, with all the loss of safety but the order of magnitude improvement in efficiency that that brings.