 Asymmetric 2-opt reversal cost

A 2-opt schedule move reverses a consecutive block $v_p,\dots ,v_q$, reconnecting its boundary arcs. With directed costs, its change isOmitting the internal sum is valid only for symmetric costs. A simulated annealing step accepts an increase with probability $\exp (-\Delta /T)$; a strictly positive temperature permits escape from local minima.