belief propagation for spatial network embeddings
play

Belief Propagation for Spatial Network Embeddings Andrew Frank - PowerPoint PPT Presentation

Belief Propagation for Spatial Network Embeddings Andrew Frank Alex Ihler Padhraic Smyth Department of Computer Science UC Irvine August 25, 2009 Outline 1 Graphical Models Markov Random Fields Inference 2 Self-Localization Problem


  1. Belief Propagation for Spatial Network Embeddings Andrew Frank Alex Ihler Padhraic Smyth Department of Computer Science UC Irvine August 25, 2009

  2. Outline 1 Graphical Models Markov Random Fields Inference 2 Self-Localization Problem Description Model Formulation Experimental Results Latent Space Embeddings of Social Networks 3 Problem Description Model Formulation Preliminary Results

  3. Graphical Models Markov Random Fields Outline 1 Graphical Models Markov Random Fields Inference 2 Self-Localization Problem Description Model Formulation Experimental Results Latent Space Embeddings of Social Networks 3 Problem Description Model Formulation Preliminary Results

  4. Graphical Models Markov Random Fields What Are Graphical Models? Concise representations of probabilistic models Several types: Bayesian networks (DAGs) Markov random fields (undirected graphs) Factor graphs (bipartite graphs) . . . and others!

  5. Graphical Models Markov Random Fields What Are Graphical Models? Concise representations of probabilistic models Several types: Bayesian networks (DAGs) Markov random fields (undirected graphs) Factor graphs (bipartite graphs) . . . and others! A Nodes = random variables B C Edges = dependencies E D between variables

  6. Graphical Models Markov Random Fields What Are Graphical Models? Concise representations of probabilistic models Several types: Bayesian networks (DAGs) Markov random fields (undirected graphs) Factor graphs (bipartite graphs) . . . and others! A suspects Nodes = random variables B C Edges = dependencies E D between variables {innocent,guilty}

  7. Graphical Models Markov Random Fields What Are Graphical Models? Concise representations of probabilistic models Several types: Bayesian networks (DAGs) Markov random fields (undirected graphs) Factor graphs (bipartite graphs) . . . and others! friends A suspects Nodes = random variables B C Edges = dependencies E D between variables {innocent,guilty}

  8. Graphical Models Markov Random Fields Representing Conditional Independencies Interpreting a Markov Random Field If all paths from X to Y pass through Z, then we can say X and Y are conditionally independent given Z. Graphically, with a Textually, through enumeration: Markov Random Field (MRF): A ⊥ D , E | C A B ⊥ C , D , E | A C ⊥ B | A B C D ⊥ A , B , E | C E D E ⊥ A , B , D | C . . .

  9. Graphical Models Markov Random Fields Factorization Conditional independence lets us factor a distribution: A A ⊥ D , E | C B ⊥ C , D , E | A B C C ⊥ B | A D ⊥ A , B , E | C E D E ⊥ A , B , D | C p ( A , B , C , D , E ) = p ( A ) p ( B | A ) p ( C | A , B ) p ( D | A , B , C ) p ( E | A , B , C , D )

  10. Graphical Models Markov Random Fields Factorization Conditional independence lets us factor a distribution: A A ⊥ D , E | C B ⊥ C , D , E | A B C C ⊥ B | A D ⊥ A , B , E | C E D E ⊥ A , B , D | C p ( A , B , C , D , E ) = p ( A ) p ( B | A ) p ( C | A , B ) p ( D | A , B , C ) p ( E | A , B , C , D )

  11. Graphical Models Markov Random Fields Factorization Conditional independence lets us factor a distribution: A A ⊥ D , E | C B ⊥ C , D , E | A B C C ⊥ B | A D ⊥ A , B , E | C E D E ⊥ A , B , D | C p ( A , B , C , D , E ) = p ( A ) p ( B | A ) p ( C | A , B ) p ( D | A , B , C ) p ( E | A , B , C , D ) = p ( A )

  12. Graphical Models Markov Random Fields Factorization Conditional independence lets us factor a distribution: A A ⊥ D , E | C B ⊥ C , D , E | A B C C ⊥ B | A D ⊥ A , B , E | C E D E ⊥ A , B , D | C p ( A , B , C , D , E ) = p ( A ) p ( B | A ) p ( C | A , B ) p ( D | A , B , C ) p ( E | A , B , C , D ) = p ( A )

  13. Graphical Models Markov Random Fields Factorization Conditional independence lets us factor a distribution: A A ⊥ D , E | C B ⊥ C , D , E | A B C C ⊥ B | A D ⊥ A , B , E | C E D E ⊥ A , B , D | C p ( A , B , C , D , E ) = p ( A ) p ( B | A ) p ( C | A , B ) p ( D | A , B , C ) p ( E | A , B , C , D ) = p ( A ) p ( B | A )

  14. Graphical Models Markov Random Fields Factorization Conditional independence lets us factor a distribution: A A ⊥ D , E | C B ⊥ C , D , E | A B C C ⊥ B | A D ⊥ A , B , E | C E D E ⊥ A , B , D | C p ( A , B , C , D , E ) = p ( A ) p ( B | A ) p ( C | A , B ) p ( D | A , B , C ) p ( E | A , B , C , D ) = p ( A ) p ( B | A )

  15. Graphical Models Markov Random Fields Factorization Conditional independence lets us factor a distribution: A A ⊥ D , E | C B ⊥ C , D , E | A B C C ⊥ B | A D ⊥ A , B , E | C E D E ⊥ A , B , D | C p ( A , B , C , D , E ) = p ( A ) p ( B | A ) p ( C | A , B ) p ( D | A , B , C ) p ( E | A , B , C , D ) = p ( A ) p ( B | A ) p ( C | A )

  16. Graphical Models Markov Random Fields Factorization Conditional independence lets us factor a distribution: A A ⊥ D , E | C B ⊥ C , D , E | A B C C ⊥ B | A D ⊥ A , B , E | C E D E ⊥ A , B , D | C p ( A , B , C , D , E ) = p ( A ) p ( B | A ) p ( C | A , B ) p ( D | A , B , C ) p ( E | A , B , C , D ) = p ( A ) p ( B | A ) p ( C | A )

  17. Graphical Models Markov Random Fields Factorization Conditional independence lets us factor a distribution: A A ⊥ D , E | C B ⊥ C , D , E | A B C C ⊥ B | A D ⊥ A , B , E | C E D E ⊥ A , B , D | C p ( A , B , C , D , E ) = p ( A ) p ( B | A ) p ( C | A , B ) p ( D | A , B , C ) p ( E | A , B , C , D ) = p ( A ) p ( B | A ) p ( C | A ) p ( D | C )

  18. Graphical Models Markov Random Fields Factorization Conditional independence lets us factor a distribution: A A ⊥ D , E | C B ⊥ C , D , E | A B C C ⊥ B | A D ⊥ A , B , E | C E D E ⊥ A , B , D | C p ( A , B , C , D , E ) = p ( A ) p ( B | A ) p ( C | A , B ) p ( D | A , B , C ) p ( E | A , B , C , D ) = p ( A ) p ( B | A ) p ( C | A ) p ( D | C )

  19. Graphical Models Markov Random Fields Factorization Conditional independence lets us factor a distribution: A A ⊥ D , E | C B ⊥ C , D , E | A B C C ⊥ B | A D ⊥ A , B , E | C E D E ⊥ A , B , D | C p ( A , B , C , D , E ) = p ( A ) p ( B | A ) p ( C | A , B ) p ( D | A , B , C ) p ( E | A , B , C , D ) = p ( A ) p ( B | A ) p ( C | A ) p ( D | C ) p ( E | C )

  20. Graphical Models Markov Random Fields Factorization Conditional independence lets us factor a distribution: A A ⊥ D , E | C B ⊥ C , D , E | A B C C ⊥ B | A D ⊥ A , B , E | C E D E ⊥ A , B , D | C p ( A , B , C , D , E ) = p ( A ) p ( B | A ) p ( C | A , B ) p ( D | A , B , C ) p ( E | A , B , C , D ) = p ( A ) p ( B | A ) p ( C | A ) p ( D | C ) p ( E | C ) Largest factor involves 2 variables!

  21. Graphical Models Markov Random Fields Hammersley-Clifford Theorem General factorization property of all MRFs: Hammersley-Clifford Theorem Every MRF factors as the product of potential functions defined over cliques of the graph. Potential functions are. . . Strictly positive Unnormalized

  22. Graphical Models Markov Random Fields Hammersley-Clifford Theorem General factorization property of all MRFs: Hammersley-Clifford Theorem Every MRF factors as the product of potential functions defined over cliques of the graph. A Potential functions are. . . B C Strictly positive E D Unnormalized p ( · ) ∝ f A ( A ) f B ( B ) f C ( C ) f D ( D ) f E ( E ) f AB ( A , B ) f AC ( A , C ) f CD ( C , D ) f CE ( C , E )

  23. Graphical Models Markov Random Fields Specifying a Markov Random Field Model Define the potential functions, e.g.: Let our domain be 0=innocent, 1=guilty. � . 4 B = 0 f B ( B ) = . 6 B = 1 � A = B 2 f AB ( A , B ) = 1 A � = B

  24. Graphical Models Markov Random Fields Specifying a Markov Random Field Model Define the potential functions, e.g.: Let our domain be 0=innocent, 1=guilty. � . 4 B = 0 Suspect B is acting suspicious. f B ( B ) = . 6 B = 1 � A = B 2 f AB ( A , B ) = 1 A � = B

  25. Graphical Models Markov Random Fields Specifying a Markov Random Field Model Define the potential functions, e.g.: Let our domain be 0=innocent, 1=guilty. � . 4 B = 0 Suspect B is acting suspicious. f B ( B ) = . 6 B = 1 � A = B 2 Suspects A and B are friends. f AB ( A , B ) = 1 A � = B

  26. Graphical Models Inference Outline 1 Graphical Models Markov Random Fields Inference 2 Self-Localization Problem Description Model Formulation Experimental Results Latent Space Embeddings of Social Networks 3 Problem Description Model Formulation Preliminary Results

  27. Graphical Models Inference Marginalization with MRFs Query p(A): � O ( d n ) p ( A ) = p ( A , B , C , D , E ) B , C , D , E

  28. Graphical Models Inference Marginalization with MRFs Query p(A): � O ( d n ) p ( A ) = p ( A , B , C , D , E ) B , C , D , E A Use graph structure to compute p(A) B C in O ( dn 2 ) . E D

  29. Graphical Models Inference Belief Propagation (Sum-Product Algorithm) View marginalization as a “message-passing” algorithm Variables are computational nodes. Intermediate results are “messages” between nodes. A B C E D � f ( A ) f ( B ) f ( C ) f ( D ) f ( E ) f ( A , B ) f ( A , C ) f ( C , D ) f ( C , E ) B , C , D , E

  30. Graphical Models Inference Belief Propagation (Sum-Product Algorithm) View marginalization as a “message-passing” algorithm Variables are computational nodes. Intermediate results are “messages” between nodes. A B C E D � f ( A ) f ( B ) f ( C ) f ( D ) f ( E ) f ( A , B ) f ( A , C ) f ( C , D ) f ( C , E ) B , C , D , E

Recommend


More recommend