A note on “Two-machine flow-shop scheduling with rejection” and its link with flow-shop scheduling and common due date assignment
Introduction
In [5] Shabtay and Gasper have recently tackled the two-machine flow-shop problem with rejection where two objectives are considered, namely the makespan and the total rejection cost, and four combinations of such objectives are analyzed. Such combinations are the problem of minimizing the weighted sum of such objectives (denoted by P1), the constraint problem with respect to the total rejection cost (denoted by P2), the constraint problem with respect to the makespan (denoted by P3) and the more general problem devoted to the search for the Pareto optimal solutions with respect to both objectives (denoted by P4). Several complexity and approximation results are provided on problems P1, …, P4 but some related literature [3], [8] on common due date assignment and flow-shop scheduling is missing. Purpose of this note is to position the contribution of [5] with respect to such literature.
Consider the more general problem P4. We have n jobs available for processing at time zero to be scheduled on m=2 machines in a flow-shop scheduling system. Each job j has a processing time aj on the first machine, a processing time bj on the second machine and a rejection cost wj. The jobs can be either accepted (belonging then to the set A of accepted jobs) or rejected (belonging then to the set of rejected jobs). The objectives are the makespan of the accepted jobs and the total rejection cost and the aim is to search for the Pareto optimal solutions with respect to both objectives.
However, as all the jobs in A will be completed within the makespan , such makespan can be seen as a common due date d to be respected by the jobs in A (hence all jobs will be early with respect to d), while the jobs in can be assumed w.l.o.g. to be completed after d (hence all jobs will be tardy with respect to d).
But then, using the extended three-field classification of [7] (which is more common for multi-objective scheduling), problem P4 can be denoted by unknown . Correspondingly, P1 can be denoted by , unknown , P2 can be denoted by , unknown and P3 can be denoted by , unknown .
It turns out that P4 is actually the weighted generalization of problem , unknown considered in [8] (denoted hereafter by P5) and is also strictly related to problem (minimization of the weighted sum of tardy jobs in a two-machine flow-shop with common due date D—denoted hereafter P6) considered in [3]. This has several implications with respect to the overall contribution of [5].
Section snippets
NP-hardness of problem P1—Section 2.1. in [5]
It can be directly derived from the NP-hardness of problem P6 proved in [3] by showing that P6 reduces to P1. Here is a sketch of the proof. Let us denote by the makespan obtained by Johnson's algorithm [2] when computing the optimal schedule for the problem. Given an instance of P6 (where we assume w.l.o.g. integer, i=1, …, n), consider solving several instances of P1 that keep the same processing times but multiplies the weights by a coefficient with . Notice that
Final remarks
In this note we positioned the contribution of [5] with respect to some relevant literature not considered in that paper. We notice, however, that, apparently, in the scheduling literature, there has been little attention in ascertaining the (dis)-similarities between scheduling with rejection and bi-objective scheduling with common due date assignment and this is particularly unfortunate in [5] as one of the authors is the author of several other publications on due date assignment such as,
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Cited by (9)
A constraint generation approach for two-machine shop problems with jobs selection
2017, European Journal of Operational ResearchCitation Excerpt :The literature on shop scheduling problems with job rejection is reviewed by Shabtay, Gasper, and Kaspi (2013). The case of the two-machine flow shop problem has been reviewed by Shabtay and Gasper (2012) while T’kindt and Della Croce (2012) provided links with common due date problems. It is mentioned there that most two-stage shop problems with job rejection are NP-hard even with the equal job rejection cost assumption.
Job selection in two-stage shops with ordered machines
2015, Computers and Industrial EngineeringA note: Minmax due-date assignment problem with lead-time cost
2013, Computers and Operations ResearchCitation Excerpt :Within the wide range of due-date assignment problems, we find three major classes (see e.g. Gordon et al. [1]): (i) assigning a common due-date for all the jobs (also known as CON), (ii) assigning job-dependent due-dates which are (linear) functions of the job processing times (also known as SLK), and (iii) assigning job-dependent due-dates which are penalized if exceed pre-specified deadlines (also known as DIF). For class (i), we refer the readers to the survey papers of Baker and Scudder [2] and of Gordon et al. [1], and to more recent papers such as Shabtay and Gasper [3], Tkindt and Della Croce [4], and Drobouchevitch and Sidney [5]. Relevant references for class (ii) contain Adamopoulos and Pappis [6], Cheng [7–9], Quaddus [10], Alidaee [11], Gordon [12], Karacapilidis and Pappis [13], De et al. [14], Oğuz and Dincer [15], Cheng et al. [16], Gordon and Strusevich [17], Cheng and Kovalyov [18], Wang [19], Shabtay and Steiner [20], Janiak et al. [21], Mosheiov and Oron [22], Wang X.-Y.and Wang M.-Z. [23], and Mor and Mosheiov [24], among others.
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