1 A multi-agent coordination model for the variation of underlying network topology Author: Yi-Chuan Jiang, J.C. Jiang Presenter: Cheng-Hsi Wu Expert Systems with Applications, 2005

2 Background In the multi-agent system With dynamic network topology Distributed agents Key problems: Task allocation Resource negotiation

3 Scenarios A multi system: Agent set A={a 1,a 2,a 3, …,a n } Agent ’ s capabilities & resources: a 1 ={c 1,c 3,c 5 } & {r 2,r 6,r 7 } a 2 ={c 3,c 6,c 8 } & {r 3,r 5,r 7,r 9 } … Task set T={t 1,t 2,t 3, …,t m } Needed resources of each task t 1 ={r 1,r 2,r 3 } t 2 ={r 3,r 4,r 7 } … Algorithms Task is allocated to agents t 1 ={a 1,a 8 } t 2 ={a 3,a 5,a 6 } … Resource negotiation t1 borrows resources from other agents

4 Task Allocation

5 Example a1a1 a2a2 a3a3 a4a4 a5a5 a6a6 a7a7 a8a8 a9a9 a 10 a 11 a 12 (8,8) (17,12) (17,19) (7,20) (23,7) (11,12) (13,2) (3,4) (5,14) (10,27) (18,25) (29,26)

6 Example =AC A C =ANA N n1n1 n 900 n 218 n 342 n 557 n 577 n 203 n 43 n 93 n 341 n 395 n 738 n 779 n 790

7 Example =TC T C t 5 ={c 2,c 4,c 6,c 8 } Agent set owns c 2 : A 2 ={a 1,a 2,a 4,a 6,a 9,a 10,a 11,a 12 } Agent set owns c 4 : A 4 ={a 2,a 5,a 6,a 9,a 11 } Agent set owns c 6 : A 6 ={a 4,a 8 } Agent set owns c 8 : A 8 ={a 7,a 8,a 11 } =AC A C

8 Two Algorithms for Task Allocation Agent set owns c 2 : A 2 ={a 1,a 2,a 4,a 6,a 9,a 10,a 11,a 12 } Agent set owns c 4 : A 4 ={a 2,a 5,a 6,a 9,a 11 } Agent set owns c 6 : A 6 ={a 4,a 8 } Agent set owns c 8 : A 8 ={a 7,a 8,a 11 } Algorithm 1: brute force (n for loops) Optimal allocation : t 5 ={a 2,a 8 } a 2 locate in n(17,12) a 8 locate in n(18,25) Distance{n(17,12),n(18,25)} =|17-18|+|12-25|=14 The shorter distance, the less cost

9 Two Algorithms for Task Allocation Algorithm 2: voting Agent set owns c 2 : A 2 ={a 1,a 2,a 4,a 6,a 9,a 10,a 11,a 12 } Agent set owns c 4 : A 4 ={a 2,a 5,a 6,a 9,a 11 } Agent set owns c 6 : A 6 ={a 4,a 8 } Agent set owns c 8 : A 8 ={a 7,a 8,a 11 } A={A 2,A 4,A 6,A 8 }={a 1,a 2,a 4,a 5,a 6,a 7,a 8,a 9,a 10,a 11,a 12 } C={c 2,c 4,c 6,c 8 } {container 1, …,container 12 }= A C 2 2 container 11 =3 Select a 11 c 6 not selectSelect a 4 C={c 2,c 4,c 6,c 8 } - {c 2,c 4, c 8 } ={c 6 } All capabilities are selectedt 5 ={a 11,a 4 }

10 Performance Comparison

11 Resource Negotiation A R =AR T R =TR t 5 is allocated to {a 2,a 8 } t 5 needs {r 1,r 2,r 3,r 5,r 6,r 7,r 8,r 9,r 10 } a 2 and a 8 have {r 2,r 4,r 7,r 8,r 9,r 10 } To borrow {r 1,r 3,r 5,r 6 }

12 Resource Negotiation A R =AR The agents set that have {r 1,r 3,r 5,r 6 } ={a 1,a 3,a 5,a 6,a 7,a 9,a 10,a 11,a 12 } t 5 is allocated to {a 2,a 8 } Re-ordered according to the distances to {a 2,a 8 } ={a 6,a 3,a 12,a 5,a 10,a 1,a 7,a 9,a 11 } T A =TA Priority: Borrows {r 1,r 3,r 5 } from a 3 The agents set that have {r6} ={a 1,a 12 } Borrows {r 6 } from a 12

13 Dynamic Network Topology

14 Dynamic Network Topology

15 Summary of Comparison

16 Conclusions Agent coordination is issued in Task allocation Resource negotiation In this paper, two more factors are considered Network topology Agent distribution