Applications_CP_LS - Chapter6 Applications of Constraint...

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1 Chapter 6 Applications of Constraint Programming and Local Search
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2 Outline Employee Scheduling Exam Timetabling Traveling Salesman Problem Car Sequencing Job-Shop Scheduling
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3 There are several real-world applications of CSPs, especially constraint-based scheduling . This chapter introduces just a few of scheduling and sequencing applications. Scheduling is the allocation, subject to constraints, of resources to objects being placed in space-time, in such a way as to minimize the total cost of some set of the resources used. Sequencing is the construction, subject to constraints, of an order in which activities are to be carried out or objects to be placed in some representation of a solution. Examples: traveling salesman problem, car sequencing.
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4 EMPLOYEE SCHEDULING   In employee scheduling problem (ETP), we are given a set of employees with various qualifications, pay- rates and availabilities. a set of shifts with skill requirements and known start and end times. The objective is to assign an employee to every shift during a time period such that the constraints are satisfied and the schedule’s cost is minimized. Example : Timetabling nurses in a department (ward) in a hospital.
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5 Example: Nurse Timetabling The nurses in a ward are of several types and they can be assigned to different roles in several types of shifts . Usually there are three shifts per day: morning, evening, and night. Timetabling period can be 2 weeks or a month. Each nurse has a list of preferred shifts for each week and a list of forbidden shifts, due to her personal wishes. Usually nurses have some limit on the total number of hours or shifts they are allowed to work, and some constraints such as: not working more than two consecutive nights. In addition, there are some global constraints, e.g. distributing night shifts equally among all nurses or distributing weekend shifts equally over a long period.
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The Constraints   There are several kinds of constraints in the employee scheduling problem: (1) Employee Clashing Constraints : An employee can not be assigned to two shifts at the same time, or be assigned during a time when the employee is not available. (2) Qualification Constraints : this constraint is violated if an employee is assigned to a shift for which the shift’s requirements are not a subset of the employee’s qualifications. (3) Exclusion Constraints : this constraint is violated if an employee is assigned to a shift that he or she should be excluded from. (4) Personnel requests are requirements given by the employees. These are mostly wishes to have some days off. Constraints of types (1), (2), (3) are hard constraints and must be
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This note was uploaded on 05/07/2011 for the course INDUSTRIAL IE 208 taught by Professor Serolbulkan during the Fall '11 term at Marmara Üniversitesi.

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Applications_CP_LS - Chapter6 Applications of Constraint...

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