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

Download Presentation
Download Policy: The content available on the website is offered to you 'AS IS' for your personal information and use only. It cannot be commercialized, licensed, or distributed on other websites without prior consent from the author. To download a presentation, simply click this link. If you encounter any difficulties during the download process, it's possible that the publisher has removed the file from their server.

Recommend


More recommend