Lena Gorelick joint work with Y. Boykov O. Veksler I. Ben Ayed A. Delong E (x) p fp xp 1 p , q Ν x 0 ,1 [ x p xq ] f Potts Model 2 E (x) u p p xp v pq x p xq x 0 ,1 p , q v pq 0 v pq Potts Model Submodular Energy global optimum with graphcut (Boros & Hammer, 2002) 3 E (x) u p p v xp pq x p x q const. p , q pq , v pq 0 Middlebury Non-Submodular Energy NP-hard Image credit: Carlos Hernandes 4 General energy - NP-hard Approximate methods: Global Linearization: QPBO, TRWS, SRMP (Kolmogorov et al. 2006, 2014) Local Linearization: parallel ICM, IPFP (Leordeanu, 2009) Message Passing: BP (Pearl 1989) 5 QPBO, TRWS, SRMP (Kolmogorov et al. 2006, 2014) E (x ) Linearize introducing large number of variables and constraints ~ min E ( y ) s .t . y C Solve relaxed LP or its dual relaxed y * Rounding integer x * Integrality Gap 6 ~ parallel ICM (Leordeanu, 2009) Et(x) large steps weak min IPFP (Leordeanu, 2009) controls step size by relaxation E (x ) x t 1 xt Integrality Gap {0 ,1} N x Bounded domain of discrete configurations 7 Local Submodular Approximation model Non-linear Two ways to control step size ~ Et(x) E (x ) xt x t 1 {0 ,1} N x Bounded domain of discrete configurations 8 Trust Region Local submodular approximation LSA-TR Auxiliary Functions = Surrogate Functions = Upper Bounds = Majorize-Minimize Local submodular upper bound LSA-AUX Never leave the discrete domain 9 Trust Region: Discrete High Order Energies Gorelick et al. 2012,2013 Relaxed Quadratic Binary Energies Levenberg Marquardt Olsson et al. 2008 Hartley & Zisserman 2004 Auxiliary Functions=Surrogate Functions =Upper Bounds = Majorize-Minimize Discrete High Order Energies Narasimhan & Bilmes 2005 Rother et al. 2006 Ben Ayed et al. 2013 10 E (x ) u p xp p v E (x) pq x p xq xt p , q x + E (x) E sub (x) E sup (x) 11 E (x) xt x E (x) E sub (x) E sup (x) 12 E (x) E (x) E sub (x) E sup (x) ~ E (x) t xt x Approximate E (x ) around x t ~ sub E t (x) E ( x ) 13 E (x) E (x) E sub (x) E sup ~ E (x) t xt (x) x Approximate E (x ) around x t Linear Approximation ~ sub approx E t (x) E ( x ) E t (x) Submodular function LSA 14 E sup ( x ) v pq x p x q , pq v pq 0 15 v pq x p x q 16 xy 0 17 xy 0 0,1 0,0 1 y 0 1,1 1,0 1 x 18 xy 0 1 y 0 1,0 1 x 19 0 x y const Linear (Unary) approximation 0,0 1 y 0 1,1 1,0 1 x 20 u x v y const 1 y 0 1 x 21 E (x) E sub (x) E sup (x) E (x ) xt x 22 ~ sub approx E t (x) E ( x ) E t (x) E (x ) ~ Et(x) x t 1 xt Newton Step x 23 ~ sub approx E t (x) E ( x ) E t (x) E (x ) ~ s.t. || x x t || d t Et(x) xt Trust Region x Trust Region Sub-Problem Constrained Submodular NP-hard! Optimization 24 L t (x) E sub (x) E approx t t || x x t || Submodular (x) Gorelick et al. 2013 Unary Terms Boykov et al. 2006 t fixed in each iteration inversely related to trust region size adjusted based on quality of approximation 25 26 Binary De-convolution All pairwise terms supermodular ? Original Img Convolved Convolved+Noise 27 QPBOI LBP Noise: N(0,0.05) QPBO (0.1 sec.) TRWS TRWS: 5000 iter. E=65.07 QPBO-I (0.2 sec.) E=66.44 SRMP SRMP: 5000 iter. E=39.06 LBP 5000 iter. E=40.15 LSA-AUX (0.04 sec) E=34.70 IPFP (0.4 sec.) E=32.90 FTR-L LSA-TR (0.3 sec.) E=21.13 28 Image QPBO QPBO-I E= -77.08 LBP E= -84.54 IPFP E= 163.25 Repulsion = Reward different across high contrast LSA-TR edges TRWS labels SRMP LSA-AUX E= -67.21 Potts, v<0 (submodular) E= -101.61 SRMP E= -120.03 with edge repulsion, v>0 (non-submodular) E= -175.05 29 dtf-chinesechar database Kappes et al., 2013 Input Img Ground Truth LSA-TR 30 31 Efficient Squared Curvature model – (Nieuwenhuis et al. 2014, poster on Friday) Potts Model Elastica Heber et al. 2012 90-degree curvature El-Zehiry&Grady, 2010 Our curvature Using LSA-TR 32 Two novel discrete optimization methods Simple, efficient, state-of-art results The code is available online - http://vision.csd.uwo.ca/code/ Extensions: Find new applications ▪ Convexity Shape Prior (in ECCV14) Alternative optimization framework with LSA ▪ Pseudo-Bounds (in ECCV14) Please come by our poster 33