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Columbia Express Algorithms and heuristics used by shipping company Yoon Keun Ane Jeongwho Lee Co- Express.

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Presentation on theme: "Columbia Express Algorithms and heuristics used by shipping company Yoon Keun Ane Jeongwho Lee Co- Express."— Presentation transcript:

1 Columbia Express Algorithms and heuristics used by shipping company Yoon Keun Ane Jeongwho Lee Co- Express

2 Service Description 24/7 shipping company with distribution centers across the U.S. Provides 24-hour service, 2-days shipping services If late, the company refunds shipping fees to the customers Co- Express

3 Company Objective & Constraints Objective : minimize overall costs including shipping costs and penalty costs Constraints – Deadlines – Carrier Capacity Co- Express

4 How to approach the problem 3 stages of the problem 1.Package Center to Main Dist. Center - Package Shipment Schedule (Knapsack) 2.MDC to Local Dist. Centers - Minimizing Carrier Cost (Bin-Packing) 3.LDC to Final Destination - Minimizing Delivery Cost (TSP) Co- Express

5 Co- Express Problem Delineation One MDC Many customers Local distribution centers at each zone (zones divided by customer population) Optimization done by each zone

6 I. Shipment Schedule to MDC 1. Package received at Columbia 2. Package scheduled by deadline to be send to MDC  Use the following integer programming to maximize the total weight of jobs that finish before their deadlines Co- Express CO- Express

7 Integer Programming Cj = shipping cost based on weight, distance and deadline Wj= Physical weight of the package This problem is NP-complete problem also called knapsack problem, and can be solved by dynamic programming Co- Express

8 II. MDC to LDC Purpose : Minimize number of trucks according to its size Motivation : No need to use huge trucks nor many trucks going from MDC to LDC Solution: “Bin-packing” Problem : Maximize utilization space in each container Co- Express

9 Graphical Interpretation Co- Express Figure 1Figure 2 We need to minimize the size of empty space which is shown by white spaces in figure 2

10 Column Generation Method CGM is used to solve bin-packing Dual variables from original LP is used to create new column of constraints that will give a better solution than orig. LP Repetition of above steps will lead to finding the optimal pattern Formulation used most frequently nowadays Co- Express

11 Bin Packing Approx. First Fit Label bins as 1, 2, 3,... Objects are considered for packing in the order 1, 2, 3,... Pack object i in bin j where j is the least index such that bin j can contain object i. Best Fit The same as FF, except that when object i is to be packed, find the bin which after accommodating object i will have the least amount of space left. Co- Express

12 III. Local Delivery Purpose: Minimize the total distance traveled by local delivery trucks Well-known NP-hard Traveling Salesman Problem Co- Express

13 Solving TSP TSP can be solved using various methods ex) Algorithm 4.4.4.5 TSP relaxation Dynamic Programming We adopted TSP relaxation method to arrive at near-optimal solution Co- Express

14 TSP relaxation Solve Relaxation t o TSP ->get vecto r X* Check to see if x* violate s any sub-tour inequality (do this by solving min-c ut problem). If not stop If so, add the sub-tour ineq. To TSP relax Co- Express

15 Limitations & Future Research Stochastic demand and processing time Hard deadline was not considered when solving II & III Minimizing cost at distribution intsct Application to real-life data Co- Express

16 Co- Express THANK YOU, ANY QUESTIONS?


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