Efficient histogram topology P parse lines Each<Q>is Each d hash distribute R R C Each s quicksort c count IS occurrences C MS merge sort M MS MS M non-deterministic n mergeEfficient histogram topology P parse lines D hash distribute S quicksort C count occurrences MS merge sort M non-deterministic merge Each Q' is: R is: Each MS C M P C S Q' R R k T k n T is: Each MS D C