Many years ago, I ran into an intermittent performance problem that was caused by a self-propagating worst case in our quicksort implementation. If you sorted a

Many years ago, I ran into an intermittent performance problem that was caused by a self-propagating worst case in our quicksort implementation. If you sorted a sequence with one item out of place in an otherwise sorted array, you would get an n-1/1 split, and the pattern would repeat itself on the larger side of the split. We fixed this by picking a pseudo-random pivot, I think.