chapter14localsearch

# Setk1selects1andsets0s1 2 selectscfromnsk i ii

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1,2,4,3), G(Sc)=67 => S4=S0=Sc Step 3: Let k=4 19 SA example Iterations 4 and 5 Step 2: V4= .49 => swap jobs in 2nd and 3rd position – Sc=(1,4,2,3), G(Sc)=72, β4=10(.9)4=6.6 – P(Sk,Sc)=47%, U4=.90 => S5=S4 Step 3: Let k=5 Step 2: V5= .11 => swap 1st and 2nd jobs – Sc=(2,1,4,3), G(Sc)=83, β5=10(.9)5=5.9 – P(Sk,Sc)=7%, U5=.61 => S6=S5 Step 3: Let k=6 Are you bored yet? 20 Tabu (taboo?) search Tabu search tries to model human memory processes A “tabu­list” is maintained throughout the search – Moves according to the items on the list are forbidden 21 Tabu search algorithm 1. Set k=1. Select S1 and set S0=S1. 2. Select Sc from N(Sk). i. ii. If the move Sk→Sc is on the tabu list set Sk+1=Sk and go to 3 If Sk→Sc is not on the tabu list set Sk+1=Sc. Add the reverse move to the top of the tabu list and delete the entry on the bottom. If G(Sc)<G(S0), set S0=Sc. 3. Set k=k+1. Stop if stopping criteria are satisfied; otherwise go to 2. 22 Tabu search example: 1||Σ wjTj Jobs 1 2 3 4 wj 4 5 3 5 pj 12 8 15 9 dj 16 26 25 27 Determine Sc by the best schedule in the neighborhood that is not tabu Use tabu­list length = 2 – The tabu list is denoted by L 23 Tabu search example Iteration 1 Step 1: S0=S1=(1,3,2,4). G(S1)=136. Set L={}. Step 2. N(S1)= {(3,1,2,4), (1,2,3,4), (1,3,4,2)} with respective cost = {174, 115, 141} => Sc=S0=S2=(1,2,3,4). Set L={(3,2)}, i.e., swapping 3 and 2 is not al...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online