MURI Meeting July 2002 Gert Lanckriet ( ) L. El Ghaoui, M. Jordan, C. Bhattacharrya, N. Cristianini, P. Bartlett U.C. Berkeley Convex Optimization in Machine Learning
QP LP QCQP SDP SOCP Advanced Convex Optimization in Machine Learning
Linear Programming (LP)
Quadratic Programming (QP)
Quadratic Constrained Quadratic Programming (QCQP)
Second Order Cone Programming (SOCP)
Semi-Definite Programming
Advanced Convex Optimization in Machine Learning
MPM: Problem Sketch (1) a T z = b : decision hyperplane
MPM: Problem Sketch (2)
MPM: Problem Sketch (3) Probability of misclassification… … for worst-case class- conditional density… … should be minimized !
MPM: Main Result (1) Marshall & Olkin / Popescu & Bertsimas ??
MPM: Main Result (2)
Lemma MPM: Main Result (3)
MPM: Main Result (4) Lemma Probabilistic Constraint Deterministic Constraint
MPM: Main Result (5)
MPM: Geometric Interpretation
MPM: Link with FDA (1)
MPM: Link with FDA (2)
MPM: Link with FDA (3)
Robustness to Estimation Errors: Robust MPM (R-MPM)
MPM: Convex Optimization to solve the problem Linear Classifier Nonlinear Classifier Kernelizing Convex Optimization: Second Order Cone Program (SOCP) ) competitive with Quadratic Program (QP) SVMs Lemma
MPM: Empirical results =1– and TSA (test-set accuracy) of the MPM, compared to BPB (best performance in Breiman's report (Arcing classifiers, 1996)) and SVMs. (averages for 50 random partitions into 90% training and 10% test sets) Comparable with existing literature, SVMs = 1- is indeed smaller than the test-set accuracy in all cases (consistent with as worst-case bound on probability of misclassification) Kernelizing leads to more powerfull decision boundaries ( linear decision boundary < nonlinear decision boundary (Gaussian kernel) )
Conclusions
Future directions
Advanced Convex Optimization in Machine Learning
The idea (1) Machine learning Kernel-based machine learning
The idea (2)
The idea (3)
training set (labelled) test set (unlabelled) The idea (4)
The idea (5)
Hard margin SVM classifiers (1)
Hard margin SVM classifiers (2)
Hard margin SVM classifiers (3)
Hard margin SVM classifiers (4)
SDP ! Hard margin SVM classifiers (5)
Optimization Learning the kernel matrix ! Learning Hard margin SVM classifiers (6)
training set (labelled) test set (unlabelled) Learning the kernel matrix ! Hard margin SVM classifiers (7)
? Hard margin SVM classifiers (8)
Hard margin SVM classifiers (9)
Hard margin SVM classifiers (10)
Hard margin SVM classifiers (11) Learning Kernel Matrix with SDP !
Empirical results hard margin SVMs
Conclusions and future directions
See also