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arXiv 1309.3000math.OC
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带线性不等式约束的置信域问题:精确SDP松弛、全局最优性和鲁棒Optimization

Trust--Region Problems with Linear Inequality Constraints: Exact SDP Relaxation, Global Optimality and Robust Optimization

V. Jeyakumar, G. Li

摘要:

球上非凸二次函数极小化的信赖域问题是求解非线性最优化问题的信赖域方法中的一个关键子问题。它具有精确半定线性规划松弛(SDP松弛)和强对偶性等性质。不幸的是,这样的属性不,在一般情况下,持有扩展的信赖域问题具有额外的线性约束。本文证明了经典信赖域问题的两个有用而强大的特征在新的维数条件下对于带线性不等式约束的扩展信赖域问题仍然成立。首先,我们建立了一类扩展信赖域问题有一个精确的SDP-松弛,它没有斯莱特约束规格。这是通过证明一个系统的二次和仿射函数参与的模型满足范围凸性时,尺寸条件得到满足。其次,我们证明了尺寸条件与斯莱特条件一起确保了一组组合的第一和第二阶拉格朗日乘子条件是必要的和充分的扩展信赖域问题的全局最优性,从而为强对偶。最后,我们证明了扩展的信赖域模型的维数条件是容易满足的,所产生的鲁棒最小二乘问题(LSP),以及作为一个等价的半定线性规划问题的鲁棒二阶锥规划模型问题(SOCP)的重新制定。这使我们得出结论,在温和的假设下,求解矩阵范数不确定性或多面体不确定性下的鲁棒(LSP)或(SOCP)相当于求解SDP,因此,它们的解可以在多项式时间内验证。

英文摘要:

The trust-region problem, which minimizes a nonconvex quadratic function over a ball, is a key subproblem in trust-region methods for solving nonlinear optimization problems. It enjoys many attractive properties such as an exact semi-definite linear programming relaxation (SDP relaxation) and strong duality. Unfortunately, such properties do not, in general, hold for an extended trust-region problem having extra linear constraints. This paper shows that two useful and powerful features of the classical trust-region problem continue to hold for an extended trust-region problem with linear inequality constraints under a new dimension condition. First, we establish that the class of extended trust-region problems has an exact SDP-relaxation, which holds without the Slater constraint qualification. This is achieved by proving that a system of quadratic and affine functions involved in the model satisfies a range-convexity whenever the dimension condition is fulfilled. Second, we show that the dimension condition together with the Slater condition ensures that a set of combined first and second-order Lagrange multiplier conditions is necessary and sufficient for global optimality of the extended trust-region problem and consequently for strong duality. Finally, we show that the dimension condition is easily satisfied for the extended trust-region model that arises from the reformulation of a robust least squares problem (LSP) as well as a robust second order cone programming model problem (SOCP) as an equivalent semi-definite linear programming problem. This leads us to conclude that, under mild assumptions, solving a robust (LSP) or (SOCP) under matrix-norm uncertainty or polyhedral uncertainty is equivalent to solving a SDP and so, their solutions can be validated in polynomial time.

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