Algorithms for Minimizing Total Cost, Bottleneck Time and Bottleneck Shipment in Transportation Problems

We consider the transportation problem of determining nonnegative shipments from a set of m warehouses with given availabilities to a set of n markets with given requirements. Three objectives are defined for each solution: (i) total cost TC (ii) bottleneck time BT (i.e., maximum transportation time for a positive shipment) and (iii) bottleneck shipment SB (i.e., total shipment over routes with bottleneck time). An algorithm is given for determining all efficient (pareto-optimal or nondominated) (TC,BT) solution pairs. The special case of this algorithm when all the unit cost coefficients are zero is shown to be the same as the algorithms for minimizing BT provided by Szwarc and Hammer. This algorithm for minimizing BT is shown to be computationally superior (takes only about a second on the average for transportation or assignment problems with m = n = 100 on the UNIVAC 1108 computer (FORTRAN V)) to the threshold algorithm for minimizing BT. The algorithm is then extended to provide not only all the efficient (TC,BT) solution pairs but also, for each such BT, all the efficient (TC,SB) solution pairs. The algorithms are based on the cost operator theory of parametric programming for the transportation problem developed by the authors.