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Papers by Jeffrey Schaller

Research paper thumbnail of Scheduling a permutation flowshop with sequence-dependent family setups to minimize total tardiness

This paper presents procedures for scheduling a permutation flowshop with sequence-dependent fami... more This paper presents procedures for scheduling a permutation flowshop with sequence-dependent family setups when the objective is to minimize total tardiness. These procedures are tested on several problem sets. The results show that neighborhood searches that include neighborhoods based on batches of jobs and genetic algorithms are most effective.

Research paper thumbnail of Efficient procedures for the weighted squared tardiness permutation flowshop scheduling problem

Flexible Services and Manufacturing Journal, Jul 2, 2019

This paper addresses a permutation flowshop scheduling problem, with the objective of minimizing ... more This paper addresses a permutation flowshop scheduling problem, with the objective of minimizing total weighted squared tardiness. The focus is on providing efficient procedures that can quickly solve medium or even large instances. Within this context, we first present multiple dispatching heuristics. These include general rules suited to various due date-related environments, heuristics developed for the problem with a linear objective function, and procedures that are suitably adapted to take the squared objective into account. Then, we describe several improvement procedures, which use one or more of three techniques. These procedures are used to improve the solution obtained by the best dispatching rule. Computational results show that the quadratic rules greatly outperform the linear counterparts, and that one of the quadratic rules is the overall best performing dispatching heuristic. The computational tests also show that all procedures significantly improve upon the initial solution. The non-dominated procedures, when considering both solution quality and runtime, are identified. The best dispatching rule, and two of the non-dominated improvement procedures, are quite efficient, and can be applied to even very largesized problems. The remaining non-dominated improvement method can provide somewhat higher quality solutions, but it may need excessive time for extremely large instances.

Research paper thumbnail of Efficient heuristics for minimizing weighted sum of squared tardiness on identical parallel machines

Computers & Industrial Engineering, May 1, 2018

Scheduling jobs on a set of identical parallel machines using efficient heuristics when the objec... more Scheduling jobs on a set of identical parallel machines using efficient heuristics when the objective is to minimize total weighted squared tardiness is considered. Two efficient heuristics and an improvement procedure are presented for the problem. These heuristics and other heuristics are tested using problem sets that represent a variety of conditions. The results show that one of the heuristics consistently performs better than the other heuristics tested. It is also shown how these heuristics can be incorporated into other procedures such as the existing Lagrangian relaxation procedure or meta-heuristics to obtain improved solutions for medium sized problems.

Research paper thumbnail of An improved branch and bound procedure for scheduling a flow line manufacturing cell

International Journal of Production Research, Nov 15, 2005

This paper presents a new branch and bound procedure for scheduling a flow-line manufacturing cel... more This paper presents a new branch and bound procedure for scheduling a flow-line manufacturing cell. This procedure and an existing procedure are tested on several problem sets with varying numbers of families, jobs and machines, and varying setup time distributions. The results show that the new procedure solves small problems dramatically faster than the existing procedure. Three heuristic procedures, based on the new branch and bound procedure, are developed. These heuristic procedures as well as a tabu search procedure are tested on problem sets with larger problem sizes. The results show that one of the new procedures generates solutions with improved makespans compared to the tabu search procedure.

Research paper thumbnail of Minimizing total earliness and tardiness in a nowait flow shop

International Journal of Production Economics, Jun 1, 2020

This paper considers the problem of scheduling jobs in a no-wait flow shop with the objective of ... more This paper considers the problem of scheduling jobs in a no-wait flow shop with the objective of minimizing total earliness and tardiness. An exact branch-and-bound algorithm is developed for the problem. Several dispatching heuristics used previously for other environments and two new heuristics were tested under a variety of conditions. It was found that one of the new heuristics consistently performed well compared to the others. An insertion search improvement procedure with speed up methods based on the structure of the problem was proposed and was found to deliver much improved solutions in a reasonable amount of time.

Research paper thumbnail of Note on Shim and Kim’s lower bounds for scheduling on identical parallel machines to minimize total tardiness

European Journal of Operational Research, Aug 1, 2009

This note introduces a new lower bound for the problem of scheduling on parallel identical machin... more This note introduces a new lower bound for the problem of scheduling on parallel identical machines to minimize total tardiness that is based on the concepts used in the two lower bounds developed by Shim and Kim [Shim, S.O., Kim, Y.D., 2007. Scheduling on parallel identical machines to minimize total tardiness. European Journal of Operational Research 177, 135–146]. The note shows that the new lower bound dominates the three lower bounds used in Shim and Kim’s branch-and-bound algorithm and can be used in place of these lower bounds to lower the enumeration required.

Research paper thumbnail of Branch-and-bound algorithms for minimizing total earliness and tardiness in a two-machine permutation flow shop with unforced idle allowed

Computers & Operations Research, Sep 1, 2019

The two-machine permutation flow shop scheduling problem with the objective of minimizing total e... more The two-machine permutation flow shop scheduling problem with the objective of minimizing total earliness and tardiness is addressed. Unforced idle time can be used to complete jobs closer to their due dates. It is shown that unforced idle time only needs to be considered on the second machine. This result is then used to extend a lower bound and dominance conditions for the single-machine problem to the two-machine permutation flow shop problem. Two branch-and-bound algorithms are developed for the problem utilizing the lower bound and dominance conditions. The algorithms are tested using instances that represent a wide variety of conditions.

Research paper thumbnail of Scheduling a permutation flow shop with family setups to minimise total tardiness

International Journal of Production Research, Apr 15, 2012

This paper presents several procedures for scheduling a permutation flow shop with family setups ... more This paper presents several procedures for scheduling a permutation flow shop with family setups when the objective is to minimise total tardiness. These procedures are tested on several problem sets with varying numbers of families, jobs, and machines, three setup time distributions, and various levels of due date tightness and variability. The results show that variable greedy algorithms are effective when solving small problems, but a neighbourhood search procedure that includes searches with a neighbourhood defined by the sequence of batches of jobs belonging to the same setup family is more effective when solving large problems. Results are also presented, showing that significant reductions in total tardiness can be obtained if the time required to perform the family setups is reduced.

Research paper thumbnail of Metaheuristics for the permutation flowshop problem with a weighted quadratic tardiness objective

Computers & Operations Research, 2022

Research paper thumbnail of An evaluation of heuristics for scheduling a non-delay permutation flow shop with family setups to minimize total earliness and tardiness

Journal of the Operational Research Society, 2012

This paper presents several procedures for developing non-delay schedules for a permutation flow ... more This paper presents several procedures for developing non-delay schedules for a permutation flow shop with family setups when the objective is to minimize total earliness and tardiness. These procedures consist of heuristics that were found to be effective for minimizing total tardiness in flow shops without family setups, modified to consider family setups and the total earliness and tardiness objective. These procedures are tested on several problem sets with varying conditions. The results show that variable greedy algorithms are effective when solving small problems, but using a genetic algorithm that includes a neighbourhood defined by the sequence of batches of jobs belonging to the same setup family is effective when solving medium-or large-sized problems. The results also show that if setup times can be reduced a significant reduction in total earliness and tardiness could result.

Research paper thumbnail of A methodology for integrating cell formation and production planning in cellular manufacturing

Research paper thumbnail of Minimizing Weighted Squared Tardiness on Identical Parallel Machines

This paper considers a problem in which there is a set of jobs to be sequenced on identical paral... more This paper considers a problem in which there is a set of jobs to be sequenced on identical parallel machines. Each job has a weight and the objective is to sequence the jobs to minimize total weighted squared tardiness. A branch-and-bound algorithm is developed for optimally solving the problem. Several dominance conditions are presented for possible inclusion in the branch-and-bound algorithm. The dominance conditions are included in the branch-and-bound algorithm which is tested on randomly generated problems. The results show that the dominance conditions improve the efficiency of the branch-and-bound algorithm.

Research paper thumbnail of Scheduling a permutation flowshop with sequence-dependent family setups to minimize total tardiness

This paper presents procedures for scheduling a permutation flowshop with sequence-dependent fami... more This paper presents procedures for scheduling a permutation flowshop with sequence-dependent family setups when the objective is to minimize total tardiness. These procedures are tested on several problem sets. The results show that neighborhood searches that include neighborhoods based on batches of jobs and genetic algorithms are most effective.

Research paper thumbnail of Scheduling in a no-wait flow shop to minimise total earliness and tardiness with additional idle time allowed

International Journal of Production Research, 2021

Research paper thumbnail of Minimizing total Earliness and tardiness in a nowait flow shop

International Journal of Production Economics

Research paper thumbnail of Efficient heuristics for minimizing weighted sum of squared tardiness on identical parallel machines

Computers & Industrial Engineering

Research paper thumbnail of Efficient procedures for the weighted squared tardiness permutation flowshop scheduling problem

Flexible Services and Manufacturing Journal

Research paper thumbnail of Branch-And-Bound Algorithms for Minimizing Total Earliness and Tardiness in a Two-Machine Permutation Flow Shop with Unforced Idle Allowed

Computers & Operations Research

Research paper thumbnail of Heuristics for Scheduling Jobs in a Permutation Flow Shop to Minimize Total Earliness and Tardiness with Unforced Idle Time Allowed

Expert Systems with Applications

Research paper thumbnail of Metaheuristics for the single machine weighted quadratic tardiness scheduling problem

Computers & Operations Research

This paper considers the single machine scheduling problem with weighted quadratic tardiness cost... more This paper considers the single machine scheduling problem with weighted quadratic tardiness costs. Three metaheuristics are presented, namely iterated local search, variable greedy and steady-state genetic algorithm procedures. These address a gap in the existing literature, which includes branch-andbound algorithms (which can provide optimal solutions for small problems only) and dispatching rules (which are efficient and capable of providing adequate solutions for even quite large instances). A simple local search procedure which incorporates problem specific information is also proposed. The computational results show that the proposed metaheuristics clearly outperform the best of the existing procedures. Also, they provide an optimal solution for all (or nearly all, in the case of the variable greedy heuristic) the smaller size problems. The metaheuristics are quite close in what regards solution quality. Nevertheless, the iterated local search method provides the best solution, though at the expense of additional computational time. The exact opposite is true for the variable greedy procedure, while the genetic algorithm is a good all-around performer.

Research paper thumbnail of Scheduling a permutation flowshop with sequence-dependent family setups to minimize total tardiness

This paper presents procedures for scheduling a permutation flowshop with sequence-dependent fami... more This paper presents procedures for scheduling a permutation flowshop with sequence-dependent family setups when the objective is to minimize total tardiness. These procedures are tested on several problem sets. The results show that neighborhood searches that include neighborhoods based on batches of jobs and genetic algorithms are most effective.

Research paper thumbnail of Efficient procedures for the weighted squared tardiness permutation flowshop scheduling problem

Flexible Services and Manufacturing Journal, Jul 2, 2019

This paper addresses a permutation flowshop scheduling problem, with the objective of minimizing ... more This paper addresses a permutation flowshop scheduling problem, with the objective of minimizing total weighted squared tardiness. The focus is on providing efficient procedures that can quickly solve medium or even large instances. Within this context, we first present multiple dispatching heuristics. These include general rules suited to various due date-related environments, heuristics developed for the problem with a linear objective function, and procedures that are suitably adapted to take the squared objective into account. Then, we describe several improvement procedures, which use one or more of three techniques. These procedures are used to improve the solution obtained by the best dispatching rule. Computational results show that the quadratic rules greatly outperform the linear counterparts, and that one of the quadratic rules is the overall best performing dispatching heuristic. The computational tests also show that all procedures significantly improve upon the initial solution. The non-dominated procedures, when considering both solution quality and runtime, are identified. The best dispatching rule, and two of the non-dominated improvement procedures, are quite efficient, and can be applied to even very largesized problems. The remaining non-dominated improvement method can provide somewhat higher quality solutions, but it may need excessive time for extremely large instances.

Research paper thumbnail of Efficient heuristics for minimizing weighted sum of squared tardiness on identical parallel machines

Computers & Industrial Engineering, May 1, 2018

Scheduling jobs on a set of identical parallel machines using efficient heuristics when the objec... more Scheduling jobs on a set of identical parallel machines using efficient heuristics when the objective is to minimize total weighted squared tardiness is considered. Two efficient heuristics and an improvement procedure are presented for the problem. These heuristics and other heuristics are tested using problem sets that represent a variety of conditions. The results show that one of the heuristics consistently performs better than the other heuristics tested. It is also shown how these heuristics can be incorporated into other procedures such as the existing Lagrangian relaxation procedure or meta-heuristics to obtain improved solutions for medium sized problems.

Research paper thumbnail of An improved branch and bound procedure for scheduling a flow line manufacturing cell

International Journal of Production Research, Nov 15, 2005

This paper presents a new branch and bound procedure for scheduling a flow-line manufacturing cel... more This paper presents a new branch and bound procedure for scheduling a flow-line manufacturing cell. This procedure and an existing procedure are tested on several problem sets with varying numbers of families, jobs and machines, and varying setup time distributions. The results show that the new procedure solves small problems dramatically faster than the existing procedure. Three heuristic procedures, based on the new branch and bound procedure, are developed. These heuristic procedures as well as a tabu search procedure are tested on problem sets with larger problem sizes. The results show that one of the new procedures generates solutions with improved makespans compared to the tabu search procedure.

Research paper thumbnail of Minimizing total earliness and tardiness in a nowait flow shop

International Journal of Production Economics, Jun 1, 2020

This paper considers the problem of scheduling jobs in a no-wait flow shop with the objective of ... more This paper considers the problem of scheduling jobs in a no-wait flow shop with the objective of minimizing total earliness and tardiness. An exact branch-and-bound algorithm is developed for the problem. Several dispatching heuristics used previously for other environments and two new heuristics were tested under a variety of conditions. It was found that one of the new heuristics consistently performed well compared to the others. An insertion search improvement procedure with speed up methods based on the structure of the problem was proposed and was found to deliver much improved solutions in a reasonable amount of time.

Research paper thumbnail of Note on Shim and Kim’s lower bounds for scheduling on identical parallel machines to minimize total tardiness

European Journal of Operational Research, Aug 1, 2009

This note introduces a new lower bound for the problem of scheduling on parallel identical machin... more This note introduces a new lower bound for the problem of scheduling on parallel identical machines to minimize total tardiness that is based on the concepts used in the two lower bounds developed by Shim and Kim [Shim, S.O., Kim, Y.D., 2007. Scheduling on parallel identical machines to minimize total tardiness. European Journal of Operational Research 177, 135–146]. The note shows that the new lower bound dominates the three lower bounds used in Shim and Kim’s branch-and-bound algorithm and can be used in place of these lower bounds to lower the enumeration required.

Research paper thumbnail of Branch-and-bound algorithms for minimizing total earliness and tardiness in a two-machine permutation flow shop with unforced idle allowed

Computers & Operations Research, Sep 1, 2019

The two-machine permutation flow shop scheduling problem with the objective of minimizing total e... more The two-machine permutation flow shop scheduling problem with the objective of minimizing total earliness and tardiness is addressed. Unforced idle time can be used to complete jobs closer to their due dates. It is shown that unforced idle time only needs to be considered on the second machine. This result is then used to extend a lower bound and dominance conditions for the single-machine problem to the two-machine permutation flow shop problem. Two branch-and-bound algorithms are developed for the problem utilizing the lower bound and dominance conditions. The algorithms are tested using instances that represent a wide variety of conditions.

Research paper thumbnail of Scheduling a permutation flow shop with family setups to minimise total tardiness

International Journal of Production Research, Apr 15, 2012

This paper presents several procedures for scheduling a permutation flow shop with family setups ... more This paper presents several procedures for scheduling a permutation flow shop with family setups when the objective is to minimise total tardiness. These procedures are tested on several problem sets with varying numbers of families, jobs, and machines, three setup time distributions, and various levels of due date tightness and variability. The results show that variable greedy algorithms are effective when solving small problems, but a neighbourhood search procedure that includes searches with a neighbourhood defined by the sequence of batches of jobs belonging to the same setup family is more effective when solving large problems. Results are also presented, showing that significant reductions in total tardiness can be obtained if the time required to perform the family setups is reduced.

Research paper thumbnail of Metaheuristics for the permutation flowshop problem with a weighted quadratic tardiness objective

Computers & Operations Research, 2022

Research paper thumbnail of An evaluation of heuristics for scheduling a non-delay permutation flow shop with family setups to minimize total earliness and tardiness

Journal of the Operational Research Society, 2012

This paper presents several procedures for developing non-delay schedules for a permutation flow ... more This paper presents several procedures for developing non-delay schedules for a permutation flow shop with family setups when the objective is to minimize total earliness and tardiness. These procedures consist of heuristics that were found to be effective for minimizing total tardiness in flow shops without family setups, modified to consider family setups and the total earliness and tardiness objective. These procedures are tested on several problem sets with varying conditions. The results show that variable greedy algorithms are effective when solving small problems, but using a genetic algorithm that includes a neighbourhood defined by the sequence of batches of jobs belonging to the same setup family is effective when solving medium-or large-sized problems. The results also show that if setup times can be reduced a significant reduction in total earliness and tardiness could result.

Research paper thumbnail of A methodology for integrating cell formation and production planning in cellular manufacturing

Research paper thumbnail of Minimizing Weighted Squared Tardiness on Identical Parallel Machines

This paper considers a problem in which there is a set of jobs to be sequenced on identical paral... more This paper considers a problem in which there is a set of jobs to be sequenced on identical parallel machines. Each job has a weight and the objective is to sequence the jobs to minimize total weighted squared tardiness. A branch-and-bound algorithm is developed for optimally solving the problem. Several dominance conditions are presented for possible inclusion in the branch-and-bound algorithm. The dominance conditions are included in the branch-and-bound algorithm which is tested on randomly generated problems. The results show that the dominance conditions improve the efficiency of the branch-and-bound algorithm.

Research paper thumbnail of Scheduling a permutation flowshop with sequence-dependent family setups to minimize total tardiness

This paper presents procedures for scheduling a permutation flowshop with sequence-dependent fami... more This paper presents procedures for scheduling a permutation flowshop with sequence-dependent family setups when the objective is to minimize total tardiness. These procedures are tested on several problem sets. The results show that neighborhood searches that include neighborhoods based on batches of jobs and genetic algorithms are most effective.

Research paper thumbnail of Scheduling in a no-wait flow shop to minimise total earliness and tardiness with additional idle time allowed

International Journal of Production Research, 2021

Research paper thumbnail of Minimizing total Earliness and tardiness in a nowait flow shop

International Journal of Production Economics

Research paper thumbnail of Efficient heuristics for minimizing weighted sum of squared tardiness on identical parallel machines

Computers & Industrial Engineering

Research paper thumbnail of Efficient procedures for the weighted squared tardiness permutation flowshop scheduling problem

Flexible Services and Manufacturing Journal

Research paper thumbnail of Branch-And-Bound Algorithms for Minimizing Total Earliness and Tardiness in a Two-Machine Permutation Flow Shop with Unforced Idle Allowed

Computers & Operations Research

Research paper thumbnail of Heuristics for Scheduling Jobs in a Permutation Flow Shop to Minimize Total Earliness and Tardiness with Unforced Idle Time Allowed

Expert Systems with Applications

Research paper thumbnail of Metaheuristics for the single machine weighted quadratic tardiness scheduling problem

Computers & Operations Research

This paper considers the single machine scheduling problem with weighted quadratic tardiness cost... more This paper considers the single machine scheduling problem with weighted quadratic tardiness costs. Three metaheuristics are presented, namely iterated local search, variable greedy and steady-state genetic algorithm procedures. These address a gap in the existing literature, which includes branch-andbound algorithms (which can provide optimal solutions for small problems only) and dispatching rules (which are efficient and capable of providing adequate solutions for even quite large instances). A simple local search procedure which incorporates problem specific information is also proposed. The computational results show that the proposed metaheuristics clearly outperform the best of the existing procedures. Also, they provide an optimal solution for all (or nearly all, in the case of the variable greedy heuristic) the smaller size problems. The metaheuristics are quite close in what regards solution quality. Nevertheless, the iterated local search method provides the best solution, though at the expense of additional computational time. The exact opposite is true for the variable greedy procedure, while the genetic algorithm is a good all-around performer.