Solving CVRP with ACO
Minimizing Travel Cost for Complex Delivery Problems
This scenario involves the Capacitated Vehicle Routing Problem,
solved using the meta-heuristics algorithm Ant Colony Optimization. Basically, VRP is a network consisting of a number of nodes
(sometimes called cities) and arcs connecting one to all others along with the corresponding costs.
Mostly, the aim is to minimize the cost in visiting each customer once and only once. The term
"capacitated" is added due to some capacity constraints on the vehicles (vcap).
Enter the problem. Some company wants to deliver loads to a number of customers. In this case, we
have 24 nodes based on the location of Germany's train stations (don't ask why). The delivery
always starts from and ends at the depot, visiting a list of customers in other cities. And then
a number of questions arise:
- How do we minimize the travel cost in terms of distance?
- How many trucks are required?
- Which cities are visited by the truck #1, #2. etc.?
- depot: [0..23], def = 0
- vcap: [200..400], def = 400
There is a way to set all the demands, but I don't think you are ready for that. 😉
VCAP: 400 vol.
ACTIVE: 14 customers
- Düsseldorf Hbf (65 vol.)
- Hannover Hbf (45 vol.)
- Aachen Hbf (95 vol.)
- Dresden Hbf (25 vol.)
- Hamburg Hbf (85 vol.)
- München Hbf (60 vol.)
- Bremen Hbf (35 vol.)
- Leipzig Hbf (45 vol.)
- Karlsruhe Hbf (85 vol.)
- Ulm Hbf (80 vol.)
- Mannheim Hbf (100 vol.)
- Kiel Hbf (55 vol.)
- Mainz Hbf (65 vol.)
- Saarbrücken Hbf (95 vol.)
Tour 1
COST: 1498.132 km
LOAD: 395 vol.
- Leipzig Hbf | 45 vol.
- Dresden Hbf | 25 vol.
- München Hbf | 60 vol.
- Ulm Hbf | 80 vol.
- Karlsruhe Hbf | 85 vol.
- Mannheim Hbf | 100 vol.
Tour 2
COST: 1311.352 km
LOAD: 380 vol.
- Hannover Hbf | 45 vol.
- Hamburg Hbf | 85 vol.
- Kiel Hbf | 55 vol.
- Bremen Hbf | 35 vol.
- Düsseldorf Hbf | 65 vol.
- Aachen Hbf | 95 vol.
Tour 3
COST: 748.522 km
LOAD: 160 vol.
- Mainz Hbf | 65 vol.
- Saarbrücken Hbf | 95 vol.
LOAD: 395 vol.
- Leipzig Hbf | 45 vol.
- Dresden Hbf | 25 vol.
- München Hbf | 60 vol.
- Ulm Hbf | 80 vol.
- Karlsruhe Hbf | 85 vol.
- Mannheim Hbf | 100 vol.
LOAD: 380 vol.
- Hannover Hbf | 45 vol.
- Hamburg Hbf | 85 vol.
- Kiel Hbf | 55 vol.
- Bremen Hbf | 35 vol.
- Düsseldorf Hbf | 65 vol.
- Aachen Hbf | 95 vol.
LOAD: 160 vol.
- Mainz Hbf | 65 vol.
- Saarbrücken Hbf | 95 vol.
#generations: 10 for global, 5 for local
#ants: 5 times #active_customers
ACO
Rel. importance of pheromones α = 1.0
Rel. importance of visibility β = 10.0
Trail persistance ρ = 0.5
Pheromone intensity Q = 10
See this wikipedia page to learn more.
NETWORK Depo: [0] Kassel-Wilhelmshöhe | Number of cities: 24 | Total loads: 935 vol. | Vehicle capacity: 400 vol. Loads: [0, 0, 65, 0, 45, 95, 0, 25, 85, 60, 35, 45, 0, 0, 85, 80, 0, 100, 55, 65, 0, 95, 0, 0] ITERATION Generation: #1 Best cost: 4349.910 | Path: [0, 2, 5, 19, 17, 9, 0, 4, 10, 8, 18, 11, 7, 15, 0, 14, 21, 0] Best cost: 4343.030 | Path: [0, 5, 2, 19, 17, 11, 7, 0, 4, 8, 18, 10, 21, 14, 0, 15, 9, 0] Best cost: 3903.867 | Path: [0, 7, 11, 4, 10, 8, 18, 2, 0, 19, 17, 14, 15, 9, 0, 5, 21, 0] Best cost: 3877.448 | Path: [0, 9, 15, 14, 17, 19, 0, 4, 8, 18, 10, 2, 5, 0, 11, 7, 21, 0] Best cost: 3711.581 | Path: [0, 17, 14, 15, 9, 11, 7, 0, 4, 10, 8, 18, 2, 5, 0, 19, 21, 0] Best cost: 3641.471 | Path: [0, 17, 14, 15, 9, 7, 11, 0, 4, 10, 8, 18, 2, 5, 0, 19, 21, 0] Generation: #2 Best cost: 3636.102 | Path: [0, 11, 7, 9, 15, 14, 17, 0, 4, 10, 8, 18, 2, 5, 0, 19, 21, 0] Generation: #3 Best cost: 3558.006 | Path: [0, 11, 7, 9, 15, 14, 17, 0, 4, 8, 18, 10, 2, 5, 0, 19, 21, 0] OPTIMIZING each tour... Current: [[0, 11, 7, 9, 15, 14, 17, 0], [0, 4, 8, 18, 10, 2, 5, 0], [0, 19, 21, 0]] No changes made. ACO RESULTS [1/395 vol./1498.132 km] Kassel-Wilhelmshöhe -> Leipzig Hbf -> Dresden Hbf -> München Hbf -> Ulm Hbf -> Karlsruhe Hbf -> Mannheim Hbf --> Kassel-Wilhelmshöhe [2/380 vol./1311.352 km] Kassel-Wilhelmshöhe -> Hannover Hbf -> Hamburg Hbf -> Kiel Hbf -> Bremen Hbf -> Düsseldorf Hbf -> Aachen Hbf --> Kassel-Wilhelmshöhe [3/160 vol./ 748.522 km] Kassel-Wilhelmshöhe -> Mainz Hbf -> Saarbrücken Hbf --> Kassel-Wilhelmshöhe OPTIMIZATION RESULT: 3 tours | 3558.006 km.