[ODE] Sweep-and-Prune space for ODE

[Pierre Terdiman]

> This is exactly the source code I tried that was 2.5 times slower than
> std::sort.  This was pretty consistent over all the sizes I tested.

FYI I tested it this week-end (once again), and that's not what I saw.

Maybe it's just my machine (vanilla Intel) and/or my compiler (VC6), but
here std::sort is 2 to 3 times slower than the code you mention. And that's
using a simple 2-arguments std::sort, not even trying to make it a rank
sorter.

So, I can only suggest people try both and see what's best on their own
(machine, compiler) configuration.

- Pierre