Network dual potential
= Network dual potential
{title2=$\pi_i$}
A vertex potential in the dual of an <uncapacitated minimum-cost flow> yields the edge inequalities $\pi_i-\pi_j\leq c_{ij}$. Its objective is $\sum_i\pi_i b_i$. Adding a common constant leaves all <network reduced costs> and the objective unchanged when total net supply is zero. Potentials tight on a <spanning tree> are fixed up to this common constant.