Tabu Search--- part II 報告者 : 王 敬 育

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

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

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)

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)

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)

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)

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

ATL before Cancellation

ATL after Cancellation

New C-Sequence Dominated by old

Later ATL before creating Tabu Element

Later ATL after creating Tabu Element

Tabu List Management by the Reverse Elimination Method

Bounded Variable Specialization of the Reverse Elimination Method

Handling Paired Attribute Moves by the Reverse Elimination Method