1. What Is Optimization?
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4. Convex Optimization Problems
Convex Optimization — Boyd & Vandenberghe 4. Convex optimization problems optimization problem in standard form • convex optimization problems • quasiconvex optimization • linear optimization • quadratic optimization • geometric programming • generalized inequality constraints • semidefinite programming • vector optimization • 4–1 Optimization problem in standard form minimize f0(x) subject to f (x) 0, i =1,...,m i ≤ hi(x)=0, i =1,...,p x Rn is the optimization variable • ∈ f : Rn R is the objective or cost function • 0 → f : Rn R, i =1,...,m, are the inequality constraint functions • i → h : Rn R are the equality constraint functions • i → optimal value: p⋆ = inf f (x) f (x) 0, i =1,...,m, h (x)=0, i =1,...,p { 0 | i ≤ i } p⋆ = if problem is infeasible (no x satisfies the constraints) • ∞ p⋆ = if problem is unbounded below • −∞ Convex optimization problems 4–2 Optimal and locally optimal points x is feasible if x dom f and it satisfies the constraints ∈ 0 ⋆ a feasible x is optimal if f0(x)= p ; Xopt is the set of optimal points x is locally optimal if there is an R> 0 such that x is optimal for minimize (over z) f0(z) subject to fi(z) 0, i =1,...,m, hi(z)=0, i =1,...,p z x≤ R k − k2 ≤ examples (with n =1, m = p =0) f (x)=1/x, dom f = R : p⋆ =0, no optimal point • 0 0 ++ f (x)= log x, dom f = R : p⋆ = • 0 − 0 ++ −∞ f (x)= x log x, dom f = R : p⋆ = 1/e, x =1/e is optimal • 0 0 ++ − f (x)= x3 3x, p⋆ = , local optimum at x =1 • 0 − −∞ Convex optimization problems 4–3 Implicit constraints the standard form optimization problem has an implicit -
Metaheuristics1
METAHEURISTICS1 Kenneth Sörensen University of Antwerp, Belgium Fred Glover University of Colorado and OptTek Systems, Inc., USA 1 Definition A metaheuristic is a high-level problem-independent algorithmic framework that provides a set of guidelines or strategies to develop heuristic optimization algorithms (Sörensen and Glover, To appear). Notable examples of metaheuristics include genetic/evolutionary algorithms, tabu search, simulated annealing, and ant colony optimization, although many more exist. A problem-specific implementation of a heuristic optimization algorithm according to the guidelines expressed in a metaheuristic framework is also referred to as a metaheuristic. The term was coined by Glover (1986) and combines the Greek prefix meta- (metá, beyond in the sense of high-level) with heuristic (from the Greek heuriskein or euriskein, to search). Metaheuristic algorithms, i.e., optimization methods designed according to the strategies laid out in a metaheuristic framework, are — as the name suggests — always heuristic in nature. This fact distinguishes them from exact methods, that do come with a proof that the optimal solution will be found in a finite (although often prohibitively large) amount of time. Metaheuristics are therefore developed specifically to find a solution that is “good enough” in a computing time that is “small enough”. As a result, they are not subject to combinatorial explosion – the phenomenon where the computing time required to find the optimal solution of NP- hard problems increases as an exponential function of the problem size. Metaheuristics have been demonstrated by the scientific community to be a viable, and often superior, alternative to more traditional (exact) methods of mixed- integer optimization such as branch and bound and dynamic programming. -
José M. Vega-Guzmán
Jos´eM. Vega-Guzm´an Curriculum Vitae Contact Department of Mathematics Tel: (409) 880-8792 Information College of Arts and Sciences Fax: (409) 880-8794 Lamar University email: [email protected] 200-C Lucas Building URL: https://sites.google.com/site/profjmvg/ Beaumont, TX 77710 Education PhD (Applied Mathematics) 2008{2013 • Arizona State University, Tempe, AZ • Co-Advisors: Sergei K. Suslov and Carlos Castillo-Chavez • Dissertation Title: Solution Methods for Certain Evolution Equations Master in Natural Sciences (Mathematics) 2006{2008 • Arizona State University, Tempe, AZ B.S. (MathEd) 2000{2005 • Universidad de Puerto Rico, Cayey, PR • Advisor: Maria A. Avi~n´o Research Interests Nonlinear Wave Propagation. Quantum Mechanics. Integrability of Nonlinear Evolution Equations. Applications of ODE's and PDE's in the Natural Sciences. Mathematical Modeling. Publications 2017 Vega{Guzm´an,J.M.; Alqahtani, R.; Zhou, Q.; Mahmood, M.F.; Moshokoa, S.P.; Ullah, M.Z.; Biswas, A.; Belic, M. Optical solitons for Lakshmanan-Porsezian-Daniel model with spatio-temporal dispersion using the method of undetermined coefficients. Optik - International Journal for Light and Electron Optics. 144, 115{123. 2017 Wang, G.; Kara, A.H.; Vega{Guzm´an,J.M.; Biswas, A. Group analysis, nonlinear self-adjointness, conser- vation laws and soliton solutions for the mKdV systems. Nonlinear Analysis: Modeling and Control. 22(3), 334{346. 2017 Vega{Guzm´an,J.M.; Ullah, M.Z.; Asma, M.; Zhou, Q.; Biswas, A. Dispersive solitons in magneto-optic waveguides. Superlattices and Microstructures. 103, 161{170. 2017 Vega{Guzm´an,J.M.; Mahmood, M.F.; Zhou, Q.; Triki, H.; Arnous, A.H.; Biswas, A.; Moshokoa, S.P.; Belic, M. -
Introduction to the Modern Calculus of Variations
MA4G6 Lecture Notes Introduction to the Modern Calculus of Variations Filip Rindler Spring Term 2015 Filip Rindler Mathematics Institute University of Warwick Coventry CV4 7AL United Kingdom [email protected] http://www.warwick.ac.uk/filiprindler Copyright ©2015 Filip Rindler. Version 1.1. Preface These lecture notes, written for the MA4G6 Calculus of Variations course at the University of Warwick, intend to give a modern introduction to the Calculus of Variations. I have tried to cover different aspects of the field and to explain how they fit into the “big picture”. This is not an encyclopedic work; many important results are omitted and sometimes I only present a special case of a more general theorem. I have, however, tried to strike a balance between a pure introduction and a text that can be used for later revision of forgotten material. The presentation is based around a few principles: • The presentation is quite “modern” in that I use several techniques which are perhaps not usually found in an introductory text or that have only recently been developed. • For most results, I try to use “reasonable” assumptions, not necessarily minimal ones. • When presented with a choice of how to prove a result, I have usually preferred the (in my opinion) most conceptually clear approach over more “elementary” ones. For example, I use Young measures in many instances, even though this comes at the expense of a higher initial burden of abstract theory. • Wherever possible, I first present an abstract result for general functionals defined on Banach spaces to illustrate the general structure of a certain result. -
On the Ekeland Variational Principle with Applications and Detours
Lectures on The Ekeland Variational Principle with Applications and Detours By D. G. De Figueiredo Tata Institute of Fundamental Research, Bombay 1989 Author D. G. De Figueiredo Departmento de Mathematica Universidade de Brasilia 70.910 – Brasilia-DF BRAZIL c Tata Institute of Fundamental Research, 1989 ISBN 3-540- 51179-2-Springer-Verlag, Berlin, Heidelberg. New York. Tokyo ISBN 0-387- 51179-2-Springer-Verlag, New York. Heidelberg. Berlin. Tokyo No part of this book may be reproduced in any form by print, microfilm or any other means with- out written permission from the Tata Institute of Fundamental Research, Colaba, Bombay 400 005 Printed by INSDOC Regional Centre, Indian Institute of Science Campus, Bangalore 560012 and published by H. Goetze, Springer-Verlag, Heidelberg, West Germany PRINTED IN INDIA Preface Since its appearance in 1972 the variational principle of Ekeland has found many applications in different fields in Analysis. The best refer- ences for those are by Ekeland himself: his survey article [23] and his book with J.-P. Aubin [2]. Not all material presented here appears in those places. Some are scattered around and there lies my motivation in writing these notes. Since they are intended to students I included a lot of related material. Those are the detours. A chapter on Nemyt- skii mappings may sound strange. However I believe it is useful, since their properties so often used are seldom proved. We always say to the students: go and look in Krasnoselskii or Vainberg! I think some of the proofs presented here are more straightforward. There are two chapters on applications to PDE. -
The Original Euler's Calculus-Of-Variations Method: Key
Submitted to EJP 1 Jozef Hanc, [email protected] The original Euler’s calculus-of-variations method: Key to Lagrangian mechanics for beginners Jozef Hanca) Technical University, Vysokoskolska 4, 042 00 Kosice, Slovakia Leonhard Euler's original version of the calculus of variations (1744) used elementary mathematics and was intuitive, geometric, and easily visualized. In 1755 Euler (1707-1783) abandoned his version and adopted instead the more rigorous and formal algebraic method of Lagrange. Lagrange’s elegant technique of variations not only bypassed the need for Euler’s intuitive use of a limit-taking process leading to the Euler-Lagrange equation but also eliminated Euler’s geometrical insight. More recently Euler's method has been resurrected, shown to be rigorous, and applied as one of the direct variational methods important in analysis and in computer solutions of physical processes. In our classrooms, however, the study of advanced mechanics is still dominated by Lagrange's analytic method, which students often apply uncritically using "variational recipes" because they have difficulty understanding it intuitively. The present paper describes an adaptation of Euler's method that restores intuition and geometric visualization. This adaptation can be used as an introductory variational treatment in almost all of undergraduate physics and is especially powerful in modern physics. Finally, we present Euler's method as a natural introduction to computer-executed numerical analysis of boundary value problems and the finite element method. I. INTRODUCTION In his pioneering 1744 work The method of finding plane curves that show some property of maximum and minimum,1 Leonhard Euler introduced a general mathematical procedure or method for the systematic investigation of variational problems. -
Subdifferential Test for Optimality
Subdifferential Test for Optimality Florence JULES and Marc LASSONDE Universit´edes Antilles et de la Guyane 97159 Pointe `aPitre, France E-mail: fl[email protected], [email protected] Abstract. We provide a first-order necessary and sufficient condition for optimality of lower semicontinuous functions on Banach spaces using the concept of subdifferential. From the sufficient condition we derive that any subdifferential operator is monotone absorbing, hence maximal monotone when the function is convex. Keywords: lower semicontinuity, subdifferential, directional derivative, first-order condition, optimality criterion, maximal monotonicity. 2010 Mathematics Subject Classification: 49J52, 49K27, 26D10, 26B25. 1 Introduction First-order sufficient conditions for optimality in terms of derivatives or directional derivatives are well known. Typical such conditions are variants of Minty variational inequalities. Let us quote for example the following simple result (see [3]): Let f be a real-valued function which is continuous on a neighbourhood D centred at a in Rn and differentiable on D \ {a}. Then, f has a local minimum value at a if (x − a) ·∇f(x) > 0 for all x ∈ D \ {a}. For first-order conditions in terms of directional derivatives, we refer to [5]. The main objective of this note is to establish a necessary and sufficient condition for optimality of nonsmooth lower semicontinuous functions on Banach spaces using subdiffer- entials. To this end, we first provide a link between the directional derivative of a function and its dual companion represented by the subdifferential (Theorem 2.1). Then, we prove a sharp version of the mean value inequality for lower semicontinuous function using directional derivative (Lemma 3.1). -
8 the Variational Principle
8 The Variational Principle 8.1 Approximate solution of the Schroedinger equation If we can’t find an analytic solution to the Schroedinger equation, a trick known as the varia- tional principle allows us to estimate the energy of the ground state of a system. We choose an unnormalized trial function Φ(an) which depends on some variational parameters, an and minimise hΦ|Hˆ |Φi E[a ] = n hΦ|Φi with respect to those parameters. This gives an approximation to the wavefunction whose accuracy depends on the number of parameters and the clever choice of Φ(an). For more rigorous treatments, a set of basis functions with expansion coefficients an may be used. The proof is as follows, if we expand the normalised wavefunction 1/2 |φ(an)i = Φ(an)/hΦ(an)|Φ(an)i in terms of the true (unknown) eigenbasis |ii of the Hamiltonian, then its energy is X X X ˆ 2 2 E[an] = hφ|iihi|H|jihj|φi = |hφ|ii| Ei = E0 + |hφ|ii| (Ei − E0) ≥ E0 ij i i ˆ where the true (unknown) ground state of the system is defined by H|i0i = E0|i0i. The inequality 2 arises because both |hφ|ii| and (Ei − E0) must be positive. Thus the lower we can make the energy E[ai], the closer it will be to the actual ground state energy, and the closer |φi will be to |i0i. If the trial wavefunction consists of a complete basis set of orthonormal functions |χ i, each P i multiplied by ai: |φi = i ai|χii then the solution is exact and we just have the usual trick of expanding a wavefunction in a basis set. -
IEOR 269, Spring 2010 Integer Programming and Combinatorial Optimization
IEOR 269, Spring 2010 Integer Programming and Combinatorial Optimization Professor Dorit S. Hochbaum Contents 1 Introduction 1 2 Formulation of some ILP 2 2.1 0-1 knapsack problem . 2 2.2 Assignment problem . 2 3 Non-linear Objective functions 4 3.1 Production problem with set-up costs . 4 3.2 Piecewise linear cost function . 5 3.3 Piecewise linear convex cost function . 6 3.4 Disjunctive constraints . 7 4 Some famous combinatorial problems 7 4.1 Max clique problem . 7 4.2 SAT (satisfiability) . 7 4.3 Vertex cover problem . 7 5 General optimization 8 6 Neighborhood 8 6.1 Exact neighborhood . 8 7 Complexity of algorithms 9 7.1 Finding the maximum element . 9 7.2 0-1 knapsack . 9 7.3 Linear systems . 10 7.4 Linear Programming . 11 8 Some interesting IP formulations 12 8.1 The fixed cost plant location problem . 12 8.2 Minimum/maximum spanning tree (MST) . 12 9 The Minimum Spanning Tree (MST) Problem 13 i IEOR269 notes, Prof. Hochbaum, 2010 ii 10 General Matching Problem 14 10.1 Maximum Matching Problem in Bipartite Graphs . 14 10.2 Maximum Matching Problem in Non-Bipartite Graphs . 15 10.3 Constraint Matrix Analysis for Matching Problems . 16 11 Traveling Salesperson Problem (TSP) 17 11.1 IP Formulation for TSP . 17 12 Discussion of LP-Formulation for MST 18 13 Branch-and-Bound 20 13.1 The Branch-and-Bound technique . 20 13.2 Other Branch-and-Bound techniques . 22 14 Basic graph definitions 23 15 Complexity analysis 24 15.1 Measuring quality of an algorithm . -
Lectures on Partial Differential Equations
Lectures on Partial Differential Equations Govind Menon1 Dec. 2005 Abstract These are my incomplete lecture notes for the graduate introduction to PDE at Brown University in Fall 2005. The lectures on Laplace’s equation and the heat equation are included here. Typing took too much work after that. I hope what is here is still useful. Andreas Kl¨ockner’s transcript of the remaining lectures is also posted on my website. Those however have not been proofread. Comments are wel- come by email. Contents 1 Laplace’s equation 3 1.1 Introduction............................ 3 1.1.1 Minimal surfaces and Laplace’s equation . 3 1.1.2 Fields and Laplace’s equation . 5 1.1.3 Motivation v. Results . 5 1.2 Notation.............................. 5 1.3 Themeanvalueinequality. 6 1.4 Maximumprinciples ....................... 8 1.5 Thefundamentalsolution . 10 1.6 Green’s function and Poisson’s integral formula . 13 1.7 The mean value property revisited . 17 1.8 Harmonic functions are analytic . 17 1.9 Compactness and convergence . 21 1.10 Perron’s method for the Dirichlet problem . 22 1.11 Energy methods and Dirichlet’s principle . 26 1.12 Potentials of measures . 28 1.13 Lebesgue’sthorn .. .. .. .. .. .. .. 30 1.14 The potential of a compact set . 33 1.15 Capacity of compact sets . 37 1 2 1.16 Variational principles for capacity . 39 2 The heat equation 43 2.1 Motivation ............................ 43 2.2 Thefundamentalsolution . 43 2.3 Uniquenessofsolutions . 47 2.4 Theweakmaximumprinciple . 48 2.5 Themeanvalueproperty . 49 2.6 Thestrongmaximumprinciple . 53 2.7 Differenceschemes . .. .. .. .. .. .. 54 2.8 Randomwalks .......................... 56 2.9 Brownianmotion ........................ -
Variational Principles Part 1A Mathematics Tripos
Preprint typeset in JHEP style - PAPER VERSION Easter 2018 Variational Principles Part 1A Mathematics Tripos Prof. P.K. Townsend DAMTP, CMS Wilberforce Road, Cambridge CB3 0WA E-mail: [email protected] Abstract: See schedules. There are two example sheets. RECOMMENDED BOOKS: (1) D.S. Lemons, Perfect Form, Princeton University Press. (2) I.M. Gelfand and S.V. Fomin, Calculus of Variations, Dover Contents 1. Variational problems and variational principles 2 1.1 Calculus for functions of many variables 4 2. Convex functions 6 2.1 First-order conditions 7 2.1.1 An alternative first-order condition 8 2.2 The Hessian and a second-order condition 9 3. Legendre transform 10 3.1 Application to Thermodynamics 13 4. Constrained variation and Lagrange multipliers 15 5. Functionals and the Euler-Lagrange equation 20 5.1 Geodesics of the Euclidean plane 22 6. First integrals and Fermat's principle 24 7. Constrained variation of functionals 27 7.1 Sturm-Liouville problem 28 7.2 Function constraints; geodesics on surfaces 30 8. Hamilton's principle 30 8.1 Central force fields 32 8.2 The Hamiltonian and Hamilton's equations 34 9. Symmetries and Noether's theorem 35 9.0.1 A shortcut 37 9.1 Application to Hamiltonian mechanics 38 10. PDEs from variational principles 39 10.1 Minimal surfaces 39 10.2 Small amplitude oscillations of a uniform string 42 10.3 Maxwell's equations from Hamilton's principle 42 11. The second variation 43 12. The Jacobi condition 47 { 1 { 1. Variational problems and variational principles We often want to know how to maximize or minimize some quantity by varying other quantities on which it depends. -
Introduction to Integer Programming – Integer Programming Models
15.053/8 March 14, 2013 Introduction to Integer Programming – Integer programming models 1 Quotes of the Day “Somebody who thinks logically is a nice contrast to the real world.” -- The Law of Thumb “Take some more tea,” the March Hare said to Alice, very earnestly. “I’ve had nothing yet,” Alice replied in an offended tone, “so I can’t take more.” “You mean you can’t take less,” said the Hatter. “It’s very easy to take more than nothing.” -- Lewis Carroll in Alice in Wonderland 2 Combinatorial optimization problems INPUT: A description of the data for an instance of the problem FEASIBLE SOLUTIONS: there is a way of determining from the input whether a given solution x’ (assignment of values to decision variables) is feasible. Typically in combinatorial optimization problems there is a finite number of possible solutions. OBJECTIVE FUNCTION: For each feasible solution x’ there is an associated objective f(x’). Minimization problem. Find a feasible solution x* that minimizes f( ) among all feasible solutions. 3 Example 1: Traveling Salesman Problem INPUT: a set N of n points in the plane FEASIBLE SOLUTION: a tour that passes through each point exactly once. OBJECTIVE: minimize the length of the tour. 4 Example 2: Balanced Partition INPUT: A set of positive integers a1, …, an FEASIBLE SOLUTION: a partition of {1, 2, … n} into two disjoint sets S and T. – S ∩ T = ∅, S∪T = {1, … , n} OBJECTIVE : minimize | ∑i∈S ai - ∑i∈T ai | Example: 7, 10, 13, 17, 20, 22 These numbers sum to 89 The best split is {10, 13, 22} and {7, 17, 20}.