
Optimiz. & Comp. Vision
Convex and Non-Convex Optimization
Christoph Schn
¨
orr
University of Mannheim, Germany
VISIONTRAIN Thematic School
Optimization Methods in Computer Vision
Les Houches, March 2006
C. Schn
¨
orr — CVGPR Group, Dept. Math. & Comp. Science

Optimiz. & Comp. Vision
Table of Contents
1 – Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 – Literatur . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3 – Convex Sets . . . . . . . . . . . . . . . . . . . . . . . . . 13
4 – Convex Functions . . . . . . . . . . . . . . . . . . . . . . 27
5 – Subgradients and Optimality . . . . . . . . . . . . . . . . 44
6 – Conjugate Duality . . . . . . . . . . . . . . . . . . . . . . 51
7 – Convex Optimization . . . . . . . . . . . . . . . . . . . . . 55
8 – Non-Convex Optimization . . . . . . . . . . . . . . . . . . 71
C. Schn
¨
orr — CVGPR Group, Dept. Math. & Comp. Science

Optimiz. & Comp. Vision 1 Introduction
1 – Introduction
Modelling in computer vision research
• problem representation (observations, states, decisions, ...)
• criterion, (visual) task
• prior knowledge
Optimization point-of-view
• variables, domain
• objective function
• constraints
C. Schn
¨
orr — CVGPR Group, Dept. Math. & Comp. Science page 3

Optimiz. & Comp. Vision 1 Introduction
Cases studies: Convex optimization
(i) Robust estimation
Non-quadratic optimization → quadratic programming
Huber’81, Mangasarian-Musicant (PAMI’00)
(ii) Total-variation denoising
Non-smooth optimization
Rudin-Osher-Fatemi (Physica’92)
Aujol-Chambolle (JMIV’04, IJCV’05)
(iii) Non-negative `
1
-norm approximation
Linear programming
similar: sparse basis pursuit
Chen-Donoho-Saunders (SIAM Rev.’01)
C. Schn
¨
orr — CVGPR Group, Dept. Math. & Comp. Science page 4

Optimiz. & Comp. Vision 1 Introduction
Cases studies: Convex optimization (cont’d)
(iv) Non-negative sparse factorization
Second-Order Cone Programming
Heiler-Schn
¨
orr (ICCV’05, ECCV’06, JMLR to appear)
(v) Low-dimensional flat euclidean embedding
Semidefinite Programming
Weinberger-Saul (CVPR’04, IJCV in press)
C. Schn
¨
orr — CVGPR Group, Dept. Math. & Comp. Science page 5
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