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:There are a number of ''agents'' and an equal number of ''tasks'', we want to search a way to assign each agent exactly one task such that the total ''cost'' of the assignment is minimized.
The cost of an assignment is determined from a ''cost function'', which gives the cost of assigning a particular agent to a particular task. The overall cost of the assignment is then equal to the sum of the costs for each agent (or the sum of the costs for each task, which is the same thing).▼
The assignment problem is a special case of another optimization problem known as the [[transportation problem]], which is a special case the [[maximal flow problem]], which in turn is a special case of a [[linear program]]. While it is possible to solve any of these problems using the [[simplex algorithm]], each problem has more efficient algorithms designed to take advantage of its special structure. It is know that an algorithm exists to solve the assignment problem within time bounded by a polynomial expression of the number of agents.
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==An example==
▲The cost of an assignment is determined from a ''cost function'', which gives the cost of assigning a particular agent to a particular task. The overall cost of the assignment is then equal to the sum of the costs for each agent (or the sum of the costs for each task, which is the same thing).
For example, suppose that a taxi firm has three taxis (the agents) available, and three customers (the tasks) wishing to be picked up as soon as possible. The firm prides itself on speedy pickups, so for each taxi the "cost" of picking up a particular customer will depend on the time taken for the taxi to reach the pickup point. The solution to the assignment problem will be whichever combination of taxis and customers results in the least total cost.
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