C&O Reading Group - Dessalegn Hirpa

Monday, June 15, 2015 4:15 pm - 4:15 pm EDT (GMT -04:00)

Title: The generalized Trust region subproblem (GTRS)

Speaker: Dessalegn Hirpa
Affiliation: University of Waterloo
Room: MC 6486

Abstract: The trust region subproblem (TRS)-the minimization of quadratic objective subject to one quadratic constraint- has many applications in diverse areas. In particular, it determines the step in trust region algorithm.

The GTRS generalizes the TRS in a sense that it consists in minimizing
a general quadratic objective subject to an upper and lower bounded
general quadratic constraint. This means, there is no definiteness
assumption on either quadratic functions. The paper characterizes the
optimality conditions for this implicit convex problem under a constraint qualification and show that it can be assumed without loss of generality. The problem is classified in to an easy and hard instances, and the paper demonstrates that the upper and lower bounded general problem can be reduced to an equivalent equality constrained problem and possibly solving the sparse system.

The paper also discusses how the Rendl-Wolkowicz algorithm proposed in
Fortin and Wolkowicz and Rendl and Wolkowicz can be extended to solve
the resulting equality constrained problem, highlighting the connection between the GTRS and the problem of finding minimum generalized eigenvalues of a parameterized matrix pencil. Finally, a numerical result is presented to illustrate the algorithm.
The presentation will be based on the following manuscript:
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