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Unformatted text preview: Advanced Operations Research Techniques IE316 Lecture 13 Dr. Ted Ralphs IE316 Lecture 13 1 Reading for This Lecture Bertsimas 4.84.9 IE316 Lecture 13 2 Polyhedral Cones Definition 1. A set C R n is a cone if x C for all and all x C . Definition 2. A polyhedron of the form P = { x R n  Ax } is called a polyhedral cone . Theorem 1. Let C R n be the polyhedral cone defined by the matrix A . Then the following are equivalent: 1. The zero vector is an extreme point of C . 2. The cone C does not contain a line. 3. The rows of A span R n . IE316 Lecture 13 3 Comments on Polyhedral Cones Notice that the origin must be a member of every cone. Furthermore, the origin is the only possible extreme point. A polyhedral cone that has the origin as an extreme point is called pointed . Graphically, a pointed cone looks like what we would ordinarily call a cone. IE316 Lecture 13 4 The Recession Cone Consider a nonempty polyhedron P = { x R n...
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 Fall '08
 Ralphs
 Operations Research

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