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An Introduction to Optimization Theory
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Outline Introduction Unconstrained optimization problem Constrained optimization problem
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Introduction Mathematically speaking, optimization is the minimization of a objective function subject to constraints on its variables. Mathematically, we have
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Introduction
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Introduction-Linear regression
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Introduction-Battery charger
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Unconstrained optimization problem Definition for unconstrained optimization problem:
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Unconstrained optimization problem
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Gradient descent algorithm
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Gradient descent algorithm may be trapped into the local extreme instead of the global extreme
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Gradient descent algorithm Methodology for choosing suitable step size α k ---- Steepest descent algorithm
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Gradient descent algorithm
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Steepest descent algorithm with quadratic cost function:
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Gradient descent algorithm Update equation:
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Newton method Summary for Newton method
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Newton method
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Procedure for Newton method
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Quasi-Newton method
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What properties of F(x (k) ) -1 should it mimic ? 1. H k should be a symmetric matrix 2. H k should with secant property
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Quasi-Newton method Typical approaches for Quasi-Newton method 1. Rank-one formula 2. DFP algorithm 3. BFGS algorithm (L-BFGS, L indicates limited-memory)
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Constrained optimization problem Definition for constrained optimization problem
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Problems with equality constraints ---- Lagrange multiplier
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Suppose x * is a local minimizer
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Karush-Kuhn-Tucker condition (KKT) From now on, we will consider the following problem
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Karush-Kuhn-Tucker condition (KKT) Note that:
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Image statistics & Image enhancement Illustration for gradient descent with projection Constrained set Ω Initial solution Projection
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Useful Matlab introductions for optimization Useful instructions included in Matlab for optimization 1. fminunc: Solver for unconstrained optimization problems 2. fmincon: Solver for constrained optimization problems 3. linprog: Solver for linear programming problems 4. quadprog: Solver for quadratic programming problems
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