A two-warehouse inventory model for deteriorating item under permissible delay in payment via particle swarm optimisation

The objective of this paper is to develop a two‐warehouse inventory model for single deteriorating item considering allowable delay in payment with two separate warehouses (one is OW, the owned warehouse and other is RW, the rented warehouse) having different preserving facilities. Shortages, if any, are allowed and partially backlogged with a rate dependent on the duration of waiting time up to the arrival of next lot. To develop this model, two different policies [inventory follows shortage (IFS) and shortage follows inventory (SFI)] have been considered. The corresponding problems have been formulated as nonlinear constrained optimisation problems and solved by different versions of quantum behaved particle swarm optimisation algorithms. Then, to illustrate and validate the model, four numerical examples have been considered and solved. Finally, to study the effect of changes of different parameters, sensitivity analyses have been carried out by changing one parameter at a time and keeping the others at their original values.