Maximizing the weighted number of just-in-time jobs in several two-machine scheduling systems

  • Authors:
  • Dvir Shabtay;Yaron Bensoussan

  • Affiliations:
  • Department of Industrial Engineering and Management, Ben-Gurion University of the Negev, Beer Sheva, Israel;Department of Industrial Engineering and Management, Ben-Gurion University of the Negev, Beer Sheva, Israel

  • Venue:
  • Journal of Scheduling
  • Year:
  • 2012

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Abstract

The problem of maximizing the weighted number of just-in-time jobs in a two-machine flow shop scheduling system is known to be $\mathcal {NP}$ -hard (Choi and Yoon in J. Shed. 10:237---243, 2007). However, the question of whether this problem is strongly or ordinarily $\mathcal{NP}$ -hard remains an open question. We provide a pseudo-polynomial time algorithm to solve this problem, proving that it is $\mathcal{NP}$ -hard in the ordinary sense. Moreover, we show how the pseudo-polynomial algorithm can be converted to a fully polynomial time approximation scheme (FPTAS). In addition, we prove that the same problem is strongly $\mathcal{NP}$ -hard for both a two-machine job shop scheduling system and a two-machine open shop scheduling system.