Journal of Global Optimization

, Volume 20, Issue 2, pp 133–154 | Cite as

Semidefinite Relaxations of Fractional Programs via Novel Convexification Techniques

  • Mohit Tawarmalani
  • Nikolaos V. Sahinidis


In a recent work, we introduced the concept of convex extensions for lower semi-continuous functions and studied their properties. In this work, we present new techniques for constructing convex and concave envelopes of nonlinear functions using the theory of convex extensions. In particular, we develop the convex envelope and concave envelope of z=x/y over a hypercube. We show that the convex envelope is strictly tighter than previously known convex underestimators of x/y. We then propose a new relaxation technique for fractional programs which includes the derived envelopes. The resulting relaxation is shown to be a semidefinite program. Finally, we derive the convex envelope for a class of functions of the type f(x,y) over a hypercube under the assumption that f is concave in x and convex in y.

Convex Envelopes Convex Extensions Fractional Programs Semidefinite Relaxations Disjunctive Programming 


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Copyright information

© Kluwer Academic Publishers 2001

Authors and Affiliations

  • Mohit Tawarmalani
    • 1
  • Nikolaos V. Sahinidis
    • 2
  1. 1.Department of Mechanical & Industrial EngineeringThe University of Illinois at Urbana-ChampaignUrbanaUSA
  2. 2.Department of Chemical EngineeringThe University of Illinois at Urbana-ChampaignUrbanaUSA

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