We consider the problem of preemptively scheduling n independent jobs {J(1),J(2), ..., J(n)} on m parallel machines {M(1),M(2), ..., M(m)}, where each job J(j) can only be processed on a prespecified subset M(j) of ma...
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We consider the problem of preemptively scheduling n independent jobs {J(1),J(2), ..., J(n)} on m parallel machines {M(1),M(2), ..., M(m)}, where each job J(j) can only be processed on a prespecified subset M(j) of machines called its processingset. The machines are linearly ordered, and the processingset of J(j) is specified by two machine indexes a(j) and b(j);i.e., M(j) = {M(aj),M(aj+1), ..., M(bj)}. The processingsets are nested;i.e., for i not equal j, we have M(i) subset of M(j), or M(j) subset of M(i),or M(j) boolean AND M(i) = phi..Our goal is to minimize the makespan. We first give an O(n logn)-time algorithm to find an optimal schedule. We then give an O(mn + nlogn)-time algorithm to find a maximal schedule, where a schedule is said to be maximal if it processes as much work as any other schedule in any time interval [0, t], t>0.
We consider the problem of scheduling n independent jobs on m parallel machines, where the machines differ in their functionality but not in their processing speeds. Each job has a restricted set of machines to which ...
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We consider the problem of scheduling n independent jobs on m parallel machines, where the machines differ in their functionality but not in their processing speeds. Each job has a restricted set of machines to which it can be assigned, called its processingset. Preemption is not allowed. Our goal is to minimize the makespan of the schedule. We study two variants of this problem: (1) the case of tree-hierarchical processingset and (2) the case of nested processing set. We first give a fast algorithm for the case of tree-hierarchical processingset with a worst-case bound of 4/3, which is better than the best known algorithm whose worst-case bound is 2. We then give a more complicated algorithm for the case of nested processing set with a worst-case bound of 5/3, which is better than the best known algorithm whose worst-case bound is 7/4. In both cases, we will give examples achieving the worst-case bounds. (C) 2010 Elsevier B.V. All rights reserved.
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