Setk1selects1andsets0s1 2 selectscfromnsk i ii

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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...
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