Markovian Analysis of a Push-Pull Merge System with Two Suppliers, An Intermediate Buffer, and Two Retailers

This paper examines a push-pull merge system with two suppliers, two retailers and an intermediate buffer (distribution centre). Two reliable non identical suppliers performing merge operations feed a buffer that is located immediately upstream of two non-identical reliable retailers. External customers arrive to each retailer with non-identical inter-arrival times that are exponentially distributed. The amount ordered from each retailer by a customer is exactly one unit. The material flows between upstream stages (suppliers) is push type, while between downstream stages (retailers) it is driven by continuous review, reorder point/order quantity inventory control policy (s,S). Both suppliers and retailers have exponential service rates. The considered system is modelled as a continuous time Markov process with discrete states. An algorithm that generates the transition matrix for any value of the parameters of the system is developed. Once the transition matrix is known the stationary probabilities can be computed and therefore the performance measures of the model under consideration can be easily evaluated.