Abstract
We consider the problem of minimising variance of completion times when n-jobs are to be processed on a single machine. This problem is known as the CTV problem. The problem has been shown to be difficult. In this paper we consider the polytope P n whose vertices are in one-to-one correspondence with the n! permutations of the processing times [p 1, p 2, ..., p n]. Thus each vertex of P n represents a sequence in which the n-jobs can be processed. We define a V-shaped local optimal solution to the CTV problem to be the V-shaped sequence of jobs corresponding to which the variance of completion times is smaller than for all the sequences adjacent to it on P n. We show that this local solution dominates V-shaped feasible solutions of the order of 2n−3 where 2n−2 is the total number of V-shaped feasible solutions.
Using adjacency structure an P n, we develop a heuristic for the CTV problem which has a running time of low polynomial order, which is exact for n ≤ 10, and whose domination number is Ω(2n−3). In the end we mention two other classes of scheduling problems for which also ADJACENT provides solutions with the same domination number as for the CTV problem.
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Sharma, P. Permutation Polyhedra and Minimisation of the Variance of Completion Times on a Single Machine. Journal of Heuristics 8, 467–485 (2002). https://doi.org/10.1023/A:1015496114938
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DOI: https://doi.org/10.1023/A:1015496114938