ABSTRACT We address resource leveling problems in a machine environment. Given a set of m machine... more ABSTRACT We address resource leveling problems in a machine environment. Given a set of m machines, one or more renewable resources, and a set of n tasks, each assigned to exactly one of the machines. Each task has a processing time, an earliest start time, a deadline, and resource requirements. There are no precedence relations between the tasks. The tasks have to be sequenced on the machines while minimizing a function of the level of resource utilization from each resource over time. We provide various complexity results including a polynomial time algorithm for a one machine special case. We also propose an exact method using various techniques to find optimal or close-to-optimal solutions. The computational experiments show that our exact method significantly outperforms heuristics and a commercial MIP solver.
The concept of holonic manufacturing is based on the cooperation of autonomous, functionally comp... more The concept of holonic manufacturing is based on the cooperation of autonomous, functionally completeentities with diverse, often conflicting goals. The paper introduces a market mechanism for coordinatingthe activities of intelligent agents that pursue their own interest by operating under bounded rationality in achanging, hardly predictable environment. The market model is used for solving dynamic order processingand scheduling problems: conflicts between
Information Control Problems in Manufacturing 2006, 2006
In addition of the four main R&D directions, i.e., adaptive manufacturing, digital manufacturing,... more In addition of the four main R&D directions, i.e., adaptive manufacturing, digital manufacturing, knowledge-based manufacturing, and networked manufacturing, emphasised by the European initiative Manufuture, two additional requirements, i.e., the real-timeness and cooperativeness of production structures are also outlined in the paper, which are of high and increasing importance. The paper highlights the main results of a national R&D project in Hungary on Digital Enterprises, Production Networks, and the main concept of a new, just started, national research project VITAL: Real-time Cooperative Enterprises.
We study a multiprocessor extension of the preemptive open shop scheduling problem, where the set... more We study a multiprocessor extension of the preemptive open shop scheduling problem, where the set of processors is partitioned into processor groups. We show that the makespan minimization problem is polynomially solvable for two multiprocessor groups even if preemptions are restricted to integral times.
International Journal of Production Economics, 2013
Recent literature on supply chain coordination offers a wide range of game theoretic and optimiza... more Recent literature on supply chain coordination offers a wide range of game theoretic and optimization approaches that ensure efficient planning in the supply chain, but assume that the involved parties have complete information about each other. However, in reality, complete information is rarely available, and those models alone do not present any incentives for the parties to reveal their private information, e.g., the cost parameters that they use when solving their planning problems.
We suggest a novel approach to modelling and solving production planning (PP) problems in make-to... more We suggest a novel approach to modelling and solving production planning (PP) problems in make-to-order production environments. This approach unifies the capacity and the material flow oriented aspects of PP. Orders are modelled as projects that compete for limited resources. The projects consist of networks of variable-intensity activities which may require several resources at the same time. The goal is
This paper was motivated by an industrial application which led to a new flow shop scheduling mod... more This paper was motivated by an industrial application which led to a new flow shop scheduling model. In this model there is an ordered set of steps S={1,..., z}, a finite set of machines M and a finite set of jobs J. Each job must go through a contiguous ...
ABSTRACT Recently, Balas and Qualizza introduced a new cut for mixed 0,1 programs, called lopside... more ABSTRACT Recently, Balas and Qualizza introduced a new cut for mixed 0,1 programs, called lopsided cut. Here we present a family of cuts that comprises the Gomory mixed integer cut at one extreme and the lopsided cut at the other.
This paper addresses a multiprocessor generalization of the preemptive open-shop scheduling probl... more This paper addresses a multiprocessor generalization of the preemptive open-shop scheduling problem. The set of processors is partitioned into two groups and the operations of the jobs may require either single processors in either group or simultaneously all processors from the same group. We consider two variants depending on whether preemptions are allowed at any fractional time point or only at integral time points. We shall show that the former problem can be solved in polynomial time, and provide sufficient conditions under which the latter problem is tractable. Applications to course scheduling and hypergraph edge coloring are also discussed. Keywords: preemptive open shop scheduling, multiprocessor operations, polynomial time algorithms 1 1 1 1 J J J J J
ABSTRACT The coupled tasks scheduling problem was originally introduced for modeling complex rada... more ABSTRACT The coupled tasks scheduling problem was originally introduced for modeling complex radar devices. It is still used for controlling such devices and applied in similar applications. This paper considers a problem of coupled tasks scheduling on a single processor, under the assumptions that all processing times are equal to 1, the gap has exact integer length L and the precedence constraints are strict. We prove that the general problem, when L is part of the input and the precedence constraints graph is a general graph, is NP-hard in the strong sense. We also show that the special case when L=2 and the precedence constraints graph is an in-tree or an out-tree, can be solved in O(n) time. KeywordsScheduling-Complexity-Coupled tasks-Exact gap
In this note we provide new complexity and algorithmic results for scheduling inventory releasing... more In this note we provide new complexity and algorithmic results for scheduling inventory releasing jobs, a new class of single machine scheduling problems proposed recently by Boysen et al. We focus on tardiness related criteria, while known results are concerned with inventory levels between fixed delivery points. Our interest is motivated by the fact that deciding whether a feasible schedule exists is NP-hard in the strong sense, provided that all delivery deadlines are fixed, and there are no restrictions on the amount of products released by the jobs, nor on the job processing times. We will establish NP-hardness results, or provide polynomial or pseudo-polynomial time algorithms for various special cases, and describe a fully polynomial approximation scheme for one of the variants with the maximum tardiness criterion.
International Journal of Production Research, 2001
ABSTRACT The paper focuses on the modelling and evaluating product end-of-life options, which is ... more ABSTRACT The paper focuses on the modelling and evaluating product end-of-life options, which is the problem of representing products and determining disassembly sequences with the objective of maximizing revenue. For the problem considered here, three algorithms were developed. The first is the algorithm to generate the product recovery graph semi-automatically for a given product liaison graph. Then, using the generated product recovery graph, another algorithm is developed to obtain optimal disassembly plans that maximize revenue. This algorithm is based on the backward calculation so that the hyperedges of the recovery graph are visited only once. Finally, to cope with uncertainties of the end-of-life products, a recovery graph questioning algorithm is suggested to find the margin of allowed revenue reduction of a given target edge that maintains the same optimal plan. Application of the three algorithms is illustrated using an example.
International Journal of Production Economics, 2013
Abstract The principal challenge of inventory control in supply chains is that the interacting au... more Abstract The principal challenge of inventory control in supply chains is that the interacting autonomous enterprises have to plan their production and logistics under information asymmetry, driven by different, often conflicting objectives. In this paper, four different ...
International Journal of Computer Integrated Manufacturing, 2009
The paper discusses the main requirements that are posed by customized mass production towards ma... more The paper discusses the main requirements that are posed by customized mass production towards managing production networks. Special emphasis is put on real-time, cooperative behaviour. We present a large-scale national industry-academia R&D project aimed at improving the performance of a production network that produces consumer goods in large quantities and variability. An integrated approach is outlined for planning and scheduling the behaviour of the system at network-, factory-and plant levels, as well as for adapting the various plans and schedules to real execution conditions. Novel, integrated solutions are described for rolling horizon production scheduling of a factory with more than 100 production lines, for real-time control of daily production supported by information fusion and simulation, as well as for cooperative component supply. The industrial deployment of the integrated systems is also presented together with some lessons of their routine application.
ABSTRACT We address resource leveling problems in a machine environment. Given a set of m machine... more ABSTRACT We address resource leveling problems in a machine environment. Given a set of m machines, one or more renewable resources, and a set of n tasks, each assigned to exactly one of the machines. Each task has a processing time, an earliest start time, a deadline, and resource requirements. There are no precedence relations between the tasks. The tasks have to be sequenced on the machines while minimizing a function of the level of resource utilization from each resource over time. We provide various complexity results including a polynomial time algorithm for a one machine special case. We also propose an exact method using various techniques to find optimal or close-to-optimal solutions. The computational experiments show that our exact method significantly outperforms heuristics and a commercial MIP solver.
In this paper we propose exact solution methods for a bilevel uncapacitated lotsizing problem wit... more In this paper we propose exact solution methods for a bilevel uncapacitated lotsizing problem with backlogs. This is an extension of the classical uncapacitated lot-sizing problem with backlogs, in which two autonomous and self-interested decision makers constitute a two-echelon supply chain. The leader buys items from the follower in order to meet external demand at lowest cost. The follower also tries to minimize its costs. Both parties may backlog. We study the leader's problem, i.e., how to determine supply requests over time to minimize its costs in view of the possible actions of the follower. We develop two mixed-integer linear programming reformulations, as well as cutting planes to cut off feasible, but suboptimal solutions. We compare the reformulations on a series of benchmark instances.
ABSTRACT We address resource leveling problems in a machine environment. Given a set of m machine... more ABSTRACT We address resource leveling problems in a machine environment. Given a set of m machines, one or more renewable resources, and a set of n tasks, each assigned to exactly one of the machines. Each task has a processing time, an earliest start time, a deadline, and resource requirements. There are no precedence relations between the tasks. The tasks have to be sequenced on the machines while minimizing a function of the level of resource utilization from each resource over time. We provide various complexity results including a polynomial time algorithm for a one machine special case. We also propose an exact method using various techniques to find optimal or close-to-optimal solutions. The computational experiments show that our exact method significantly outperforms heuristics and a commercial MIP solver.
The concept of holonic manufacturing is based on the cooperation of autonomous, functionally comp... more The concept of holonic manufacturing is based on the cooperation of autonomous, functionally completeentities with diverse, often conflicting goals. The paper introduces a market mechanism for coordinatingthe activities of intelligent agents that pursue their own interest by operating under bounded rationality in achanging, hardly predictable environment. The market model is used for solving dynamic order processingand scheduling problems: conflicts between
Information Control Problems in Manufacturing 2006, 2006
In addition of the four main R&D directions, i.e., adaptive manufacturing, digital manufacturing,... more In addition of the four main R&D directions, i.e., adaptive manufacturing, digital manufacturing, knowledge-based manufacturing, and networked manufacturing, emphasised by the European initiative Manufuture, two additional requirements, i.e., the real-timeness and cooperativeness of production structures are also outlined in the paper, which are of high and increasing importance. The paper highlights the main results of a national R&D project in Hungary on Digital Enterprises, Production Networks, and the main concept of a new, just started, national research project VITAL: Real-time Cooperative Enterprises.
We study a multiprocessor extension of the preemptive open shop scheduling problem, where the set... more We study a multiprocessor extension of the preemptive open shop scheduling problem, where the set of processors is partitioned into processor groups. We show that the makespan minimization problem is polynomially solvable for two multiprocessor groups even if preemptions are restricted to integral times.
International Journal of Production Economics, 2013
Recent literature on supply chain coordination offers a wide range of game theoretic and optimiza... more Recent literature on supply chain coordination offers a wide range of game theoretic and optimization approaches that ensure efficient planning in the supply chain, but assume that the involved parties have complete information about each other. However, in reality, complete information is rarely available, and those models alone do not present any incentives for the parties to reveal their private information, e.g., the cost parameters that they use when solving their planning problems.
We suggest a novel approach to modelling and solving production planning (PP) problems in make-to... more We suggest a novel approach to modelling and solving production planning (PP) problems in make-to-order production environments. This approach unifies the capacity and the material flow oriented aspects of PP. Orders are modelled as projects that compete for limited resources. The projects consist of networks of variable-intensity activities which may require several resources at the same time. The goal is
This paper was motivated by an industrial application which led to a new flow shop scheduling mod... more This paper was motivated by an industrial application which led to a new flow shop scheduling model. In this model there is an ordered set of steps S={1,..., z}, a finite set of machines M and a finite set of jobs J. Each job must go through a contiguous ...
ABSTRACT Recently, Balas and Qualizza introduced a new cut for mixed 0,1 programs, called lopside... more ABSTRACT Recently, Balas and Qualizza introduced a new cut for mixed 0,1 programs, called lopsided cut. Here we present a family of cuts that comprises the Gomory mixed integer cut at one extreme and the lopsided cut at the other.
This paper addresses a multiprocessor generalization of the preemptive open-shop scheduling probl... more This paper addresses a multiprocessor generalization of the preemptive open-shop scheduling problem. The set of processors is partitioned into two groups and the operations of the jobs may require either single processors in either group or simultaneously all processors from the same group. We consider two variants depending on whether preemptions are allowed at any fractional time point or only at integral time points. We shall show that the former problem can be solved in polynomial time, and provide sufficient conditions under which the latter problem is tractable. Applications to course scheduling and hypergraph edge coloring are also discussed. Keywords: preemptive open shop scheduling, multiprocessor operations, polynomial time algorithms 1 1 1 1 J J J J J
ABSTRACT The coupled tasks scheduling problem was originally introduced for modeling complex rada... more ABSTRACT The coupled tasks scheduling problem was originally introduced for modeling complex radar devices. It is still used for controlling such devices and applied in similar applications. This paper considers a problem of coupled tasks scheduling on a single processor, under the assumptions that all processing times are equal to 1, the gap has exact integer length L and the precedence constraints are strict. We prove that the general problem, when L is part of the input and the precedence constraints graph is a general graph, is NP-hard in the strong sense. We also show that the special case when L=2 and the precedence constraints graph is an in-tree or an out-tree, can be solved in O(n) time. KeywordsScheduling-Complexity-Coupled tasks-Exact gap
In this note we provide new complexity and algorithmic results for scheduling inventory releasing... more In this note we provide new complexity and algorithmic results for scheduling inventory releasing jobs, a new class of single machine scheduling problems proposed recently by Boysen et al. We focus on tardiness related criteria, while known results are concerned with inventory levels between fixed delivery points. Our interest is motivated by the fact that deciding whether a feasible schedule exists is NP-hard in the strong sense, provided that all delivery deadlines are fixed, and there are no restrictions on the amount of products released by the jobs, nor on the job processing times. We will establish NP-hardness results, or provide polynomial or pseudo-polynomial time algorithms for various special cases, and describe a fully polynomial approximation scheme for one of the variants with the maximum tardiness criterion.
International Journal of Production Research, 2001
ABSTRACT The paper focuses on the modelling and evaluating product end-of-life options, which is ... more ABSTRACT The paper focuses on the modelling and evaluating product end-of-life options, which is the problem of representing products and determining disassembly sequences with the objective of maximizing revenue. For the problem considered here, three algorithms were developed. The first is the algorithm to generate the product recovery graph semi-automatically for a given product liaison graph. Then, using the generated product recovery graph, another algorithm is developed to obtain optimal disassembly plans that maximize revenue. This algorithm is based on the backward calculation so that the hyperedges of the recovery graph are visited only once. Finally, to cope with uncertainties of the end-of-life products, a recovery graph questioning algorithm is suggested to find the margin of allowed revenue reduction of a given target edge that maintains the same optimal plan. Application of the three algorithms is illustrated using an example.
International Journal of Production Economics, 2013
Abstract The principal challenge of inventory control in supply chains is that the interacting au... more Abstract The principal challenge of inventory control in supply chains is that the interacting autonomous enterprises have to plan their production and logistics under information asymmetry, driven by different, often conflicting objectives. In this paper, four different ...
International Journal of Computer Integrated Manufacturing, 2009
The paper discusses the main requirements that are posed by customized mass production towards ma... more The paper discusses the main requirements that are posed by customized mass production towards managing production networks. Special emphasis is put on real-time, cooperative behaviour. We present a large-scale national industry-academia R&D project aimed at improving the performance of a production network that produces consumer goods in large quantities and variability. An integrated approach is outlined for planning and scheduling the behaviour of the system at network-, factory-and plant levels, as well as for adapting the various plans and schedules to real execution conditions. Novel, integrated solutions are described for rolling horizon production scheduling of a factory with more than 100 production lines, for real-time control of daily production supported by information fusion and simulation, as well as for cooperative component supply. The industrial deployment of the integrated systems is also presented together with some lessons of their routine application.
ABSTRACT We address resource leveling problems in a machine environment. Given a set of m machine... more ABSTRACT We address resource leveling problems in a machine environment. Given a set of m machines, one or more renewable resources, and a set of n tasks, each assigned to exactly one of the machines. Each task has a processing time, an earliest start time, a deadline, and resource requirements. There are no precedence relations between the tasks. The tasks have to be sequenced on the machines while minimizing a function of the level of resource utilization from each resource over time. We provide various complexity results including a polynomial time algorithm for a one machine special case. We also propose an exact method using various techniques to find optimal or close-to-optimal solutions. The computational experiments show that our exact method significantly outperforms heuristics and a commercial MIP solver.
In this paper we propose exact solution methods for a bilevel uncapacitated lotsizing problem wit... more In this paper we propose exact solution methods for a bilevel uncapacitated lotsizing problem with backlogs. This is an extension of the classical uncapacitated lot-sizing problem with backlogs, in which two autonomous and self-interested decision makers constitute a two-echelon supply chain. The leader buys items from the follower in order to meet external demand at lowest cost. The follower also tries to minimize its costs. Both parties may backlog. We study the leader's problem, i.e., how to determine supply requests over time to minimize its costs in view of the possible actions of the follower. We develop two mixed-integer linear programming reformulations, as well as cutting planes to cut off feasible, but suboptimal solutions. We compare the reformulations on a series of benchmark instances.
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Papers by Tamás Kis