An affine-scaling derivative-free trust-region method for solving nonlinear systems subject to linear inequality constraints

In this paper, an affine-scaling derivative-free trust-region method with interior backtracking line search technique is considered for solving nonlinear systems subject to linear inequality constraints. The proposed algorithm is designed to take advantage of the problem structured by building polynomial interpolation models for each function in the nonlinear system function F. The proposed approach is developed by forming a quadratic model with an appropriate quadratic function and scaling matrix: there is no need to handle the constraints explicitly. By using both trust-region strategy and interior backing line search technique, each iteration switches to backtracking step generated by the trust-region subproblem and satisfies strict interior point feasibility by line search backtracking technique. Under reasonable conditions, the global convergence and fast local convergence rate of the proposed algorithm are established. The results of numerical experiments are reported to show the effectiveness of the proposed algorithms.     

一种求解非线性约束优化全局最优的新方法

本文提出了一种求解非线性约束优化的全局最优的新方法—它是基于利用非线性互补函数和不断增加新的约束来重复解库恩-塔克条件的非线性方程组的新方法。因为库恩-塔克条件是非线性约束优化的必要条件,得到的解未必是非线性约束优化的全局最优解,为此,本文首次给出了通过利用该优化问题的先验知识,不断地增加约束来限制全局最优解范围的方法,一些仿真例子表明提出的方法和理论有效的,并且可行的。     

改进的粒子群算法求解非线性约束优化问题

提出了一种改进的粒子群算法（Improved Particle Swarm Optimization,IPSO）,使用了一种新型的变异策略,并在搜索过程中将部分邻近的个体聚集成核,从而形成多子群引导粒子探测新的搜索区域,采用了简单易行的罚函数约束处理机制,使算法在求解较难的非线性约束优化问题时具有很强的全局搜索能力与效率。对比数值实验结果表明,该算法能够有效、稳定地求解非线性约束优化问题。     

一类非线性两层规划问题的递阶优化解法

提出一种求解一类非线性两层规划问题的新方法．通过引入解耦向量将非线性两层规划问题分解为独立且易于求解的子问题，利用两级递阶结构第1级求解若干优化的子问题，而在第2级利用第1级求解的结果调整解耦向量．所提出的方法借助于分解一协调原理并按迭代方式最终求得问题的最优解．对于含整数的规划问题，通过连续化处理后也可按该方法方便地求解．算例表明所提出的算法是简便而有效的．     

非线性约束优化问题的自适应差分进化算法

提出了一种非线性约束优化问题改进的自适应差分进化算法。该算法对差分进化算法中固定的加权因子和交叉概率因子进行改进;定义了约束违反度函数,将约束优化问题转化为无约束双目标优化问题,在每次迭代中按照约束违反度的大小保留一部分性能较优不可行粒子,有效地维持了种群的多样性;为了扩大粒子的搜索范围引入变异算子。数值实验表明,新算法具有较快的收敛速度和较好的全局寻优能力。     

Hydrodynamic design using a derivative-free method

A derivative-free shape optimization tool for computational fluid dynamics (CFD) is developed in order to facilitate the implementation of complex flow solvers in the design procedure. A modified Rosenbrocks method is used, which needs neither gradient evaluations nor approximations. This approach yields a robust and flexible tool and gives the capability of performing optimizations involving complex configurations and phenomena. The flow solver implemented solves the Reynolds-averaged Navier–Stokes equations (RANSE) on unstructured grids, using near-wall, low-Reynolds-number turbulence models. Free surface effects are taken into account by a pseudosteady surface tracking method. A mesh deformation strategy based on both lineal and torsional springs analogies is used to update the mesh while maintaining the quality of the grid near the wall for two-dimensional problems. A free-form-deformation technique is used to manage the mesh and the shape perturbations for three-dimensional cases. Two hydrodynamic applications are presented, concerning first the design of a two-dimensional hydrofoil in relation with the free-surface elevation and then the three-dimensional optimization of a hull shape, at full scale.     

非线性约束优化的算法分析

针对非线性约束优化问题,运用了一种新的智能优化算法——社会认知优化算法。社会认知优化算法是一种基于社会认知理论的集群智能优化算法,它对目标函数的解析性质没有要求,适合于大规模约束问题处理的优点,使搜索不容易陷入局部最优。将该算法引入非线性约束问题,解决优化问题。通过实例和其他算法进行比较,对比数值实验结果表明,即使只有一个学习主体,该算法能够高效、稳定地得到解决方案,便于求解非线性约束优化问题。     

一类动态非线性约束优化问题的新解法

动态非线性约束优化是一类复杂的动态优化问题,其求解的困难主要在于如何处理问题的约束及时间（环境）变量。给出了一类定义在离散时间（环境）空间上的动态非线性约束优化问题的新解法,从问题的约束条件出发构造了一个新的动态熵函数,利用此函数将原优化问题转化成了两个目标的动态优化问题。进一步设计了新的杂交算子和带局部搜索的变异算子,提出了一种新的多目标优化求解进化算法。通过对两个动态非线性约束优化问题的计算仿真,表明该算法是有效的。     

一类非线性极大极小问题的极大熵社会认知算法

针对一类非线性极大极小问题目标函数非光滑的特点给求解带来的困难,利用社会认知算法并结合极大熵函数法给出了此类问题的一种新的有效算法。首先利用极大熵函数将原问题转化为一个光滑无约束优化问题,然后利用社会认知算法对其进行求解。该算法是基于社会认知理论,通过一系列的学习代理来模拟人类的社会性以及智能性从而完成对目标的优化。数值结果表明,该算法收敛快,数值稳定性好,是求解非线性极大极小问题的一种有效算法。     

Efficient two-step derivative-free iterative methods with memory and their dynamics

In this paper, we present a family of three-parameter derivative-free iterative methods with and without memory for solving nonlinear equations. The convergence order of the new method without memory is four requiring three functional evaluations. Based on the new fourth-order method without memory, we present a family of derivative-free methods with memory. Using three self-accelerating parameters, calculated by Newton interpolatory polynomials, the convergence order of the new methods with memory are increased from 4 to 7.0174 and 7.5311 without any additional calculations. Compared with the existing methods with memory, the new method with memory can obtain higher convergence order by using relatively simple self-accelerating parameters. Numerical comparisons are made with some known methods by using the basins of attraction and through numerical computations to demonstrate the efficiency and the performance of the presented methods.     

Numerical solution of KKT systems in PDE-constrained optimization problems via the affine scaling trust-region approach†

A recently proposed trust-region approach for bound-constrained nonlinear equations is applied to the Karush-Kuhn-Tucker (KKT) system arising from the discretization of a class of partial differential equation (PDE)-constrained optimization problems. Two different implementations are developed that take into account the large dimension and the special structure of the problems. The linear algebra phase is analysed considering the possibility of solving the arising linear systems by either direct methods or short-recurrence iterative linear solvers. Viability of the approach is proved through several numerical experiments on large KKT systems arising from the discretization of control problems.     

A trust-region algorithm combining line search filter technique for nonlinear constrained optimization

In this paper, we propose a trust-region algorithm in association with line search filter technique for solving nonlinear equality constrained programming. At current iteration, a trial step is formed as the sum of a normal step and a tangential step which is generated by trust-region subproblem and the step size is decided by interior backtracking line search together with filter methods. Then, the next iteration is determined. This is different from general trust-region methods in which the next iteration is determined by the ratio of the actual reduction to the predicted reduction. The global convergence analysis for this algorithm is presented under some reasonable assumptions and the preliminary numerical results are reported.     

A new trust-region method with line search for solving symmetric nonlinear equations

A new trust-region method is proposed for symmetric nonlinear equations. In this given algorithm, if the trial step is unsuccessful, one line search will be used instead of repeatedly solving the subproblem of the normal trust-region method. Moreover, the global convergence is established under mild conditions by a new way. The quadratic convergence of the presented method is also proved. Numerical results show that the method is interesting for the given problems.     

求解约束优化问题的改进型免疫算法

为了提高免疫算法求解约束优化问题的性能,给出了一种融合乘子法的免疫算法。设计了乘子法对约束条件的转换过程,给出了基于实数编码的克隆变异算子、浓度抑制算子和免疫算法框架,并对标准测试函数进行了实验验证。实验结果表明,该算法优于文献算法,具有较好的应用价值。     

Successive Chebyshev pseudospectral convex optimization method for nonlinear optimal control problems

This article aims at proposing a successive Chebyshev pseudospectral convex optimization method for solving general nonlinear optimal control problems (OCPs). First, Chebyshev pseudospectral discrete scheme is used to discretize a general nonlinear OCP. At the same time, a convex subproblem is formulated by using the first-order Taylor expansion to convexify the discretized nonlinear dynamic constraints. Second, a trust-region penalty term is added to the performance index of the subproblem, and a successive convex optimization algorithm is proposed to solve the subproblem iteratively. Noted that the trust-region penalty parameters can be adjusted according to the linearization error in iterative process, which improves convergence rate. Third, the Karush–Kuhn–Tucker conditions of the subproblem are derived, and furthermore, a proof is given to show that the algorithm will iteratively converge to the subproblem. Additionally, the global convergence of the algorithm is analyzed and proved, which is based on three key lemmas. Finally, the orbit transfer problem of spacecraft is used to test the performance of the proposed method. The simulation results demonstrate the optimal control is bang-bang form, which is consistent with the result of theoretical proof. Also, the algorithm is of efficiency, fast convergence rate, and high accuracy. Therefore, the proposed method provides a new approach for solving nonlinear OCPs online and has great potential in engineering practice.     

A trust region method based on a new affine scaling technique for simple bounded optimization

In this paper, we propose a new trust region affine scaling method for nonlinear programming with simple bounds. Our new method is an interior-point trust region method with a new scaling technique. The scaling matrix depends on the distances of the current iterate to the boundaries, the gradient of the objective function and the trust region radius. This scaling technique is different from the existing ones. It is motivated by our analysis of the linear programming case. The trial step is obtained by minimizing the quadratic approximation to the objective function in the scaled trust region. It is proved that our algorithm guarantees that at least one accumulation point of the iterates is a stationary point. Preliminary numerical experience on problems with simple bounds from the CUTEr collection is also reported. The numerical performance reveals that our method is effective and competitive with the famous algorithm LANCELOT. It also indicates that the new scaling technique is very effective and might be a good alternative to that used in the subroutine fmincon from Matlab optimization toolbox.     

Dynamic PSO method for nonlinear constrained programming problems

A new approach is presented to solve the nonlinear constrained programming problems. Firstly, the nonlinear constrained programming problem is transformed into a bi-ohjective optimization problem. Based on the reasonable design of the searching operation and different parameters, a new dynamic particle swarm optimization algorithm （TS-MC） is proposed. The numerical experiments show that the proposed algorithm is effective in dealing with the nonlinear constrained programming problems.     

非线性互补问题的粒子群算法

针对非线性互补问题求解的困难,利用粒子群算法并结合极大熵函数法给出了该类问题的一种新的有效算法。该算法首先利用极大熵函数将非线性互补问题转化为一个无约束最优化问题,将该函数作为粒子群算法的适应值函数;然后应用粒子群算法来优化该问题。数值结果表明,该算法收敛快、数值稳定性较好,是求解非线性互补问题的一种有效算法。     

多约束非均匀线阵天线的粒子群布阵优化算法*

为了有效解决孔径约束的非均匀线阵天线优化问题,提出一种动态边界计算的粒子群算法,并在优化过程中利用多种群协作提高优化稳定性。实验仿真显示,该算法可以快速得到满意解,有效地解决非线性优化中的约束问题,提高算法收敛速度和解的质量。