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Tabu Search--- part II 報告者 : 王 敬 育
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Short-term memory Handled by treating the tabu list as a circular list size : t Perform effectively for driving the search beyond local optima and obtaining progressively improved solutions Aspiration criteria
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Long-term memory Endow the memory structures with a flexibility to choose the “ most attractive ” moves by evaluation function Doesn ’ t restrict evaluations to measures of “ ascent ” and “ descent ” , but more adaptive and varied measures
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Tabu List Strategies for Single Attribute Moves TL is a vector of attributes which impart a tabu classification to moves that contain these attributes TL = (e(1) , e(2) , … e(q)) Identify the list of solutions (x(1) , x(2) , … x(q)) such that , for each i , e(i) is the attribute associated with the move applied to x(i) to prevent this move from being reversed to return to x(i)
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Tabu List Strategies for Single Attribute Moves e(i) & e(i) ex : if x(i) → x(i+1) , e(i) set x j =1 and x(i+1) → x(i) , e(i) set x j =0 in the sequence e(p) , … e(q) , if any e(r) is followed by an element e(s) such that e(r) = e(s) the e(r) is said to be canceled by the first such e(s)
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Tabu Status Based on Cancellation Sequences active tabu list , ATL , consists only of the element of TL that have not been canceled ATL = (e(p) , … e(q)) An element e(p+1) is added to ATL , where e(q+1) = e(q) , and e(q+1) cancle an earlier element e(i) of ATL as a result of e(q+1) = e(i)
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Tabu Status Based on Cancellation Sequences The structure of ATL , upon adding e(q+1) but berore dropping e(i) , may be depicted as follows : ATL = (e(p) , … e(h) , e(i) , e(j) … e(q) , e(q+1) ) Cancellation Sequence , or C-Sequence : lies between the canceling element e(q+1) and the canceled element e(i)
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Tabu Status Based on Cancellation Sequences startseq(e) & endseq(e) startseq(e) denote the element f on ATL that starts the C-Sequence terminated by e endseq(e) denote the element g on ATL that end the C-Sequence initial by e
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ATL before Cancellation
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ATL after Cancellation
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New C-Sequence Dominated by old
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Later ATL before creating Tabu Element
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Later ATL after creating Tabu Element
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Tabu List Management by the Reverse Elimination Method
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Bounded Variable Specialization of the Reverse Elimination Method
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Handling Paired Attribute Moves by the Reverse Elimination Method
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