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Published byCecil McKenzie Modified over 8 years ago
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Daphne Koller Variable Elimination Variable Elimination Algorithm Probabilistic Graphical Models Inference
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Daphne Koller Elimination in Chains ABC E D X
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Daphne Koller Elimination in Chains ABC E D X X
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Daphne Koller C D I SG L J H D Variable Elimination Goal: P(J) Eliminate: C,D,I,H,G,S,L Compute
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Daphne Koller Variable Elimination Goal: P(J) Eliminate: D,I,H,G,S,L C D I SG L J H D Compute
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Daphne Koller Variable Elimination Goal: P(J) Eliminate: I,H,G,S,L C D I SG L J H D Compute
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Daphne Koller Variable Elimination Goal: P(J) Eliminate: H,G,S,L C D I SG L J H D Compute
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Daphne Koller Variable Elimination Goal: P(J) Eliminate: G,S,L C D I SG L J H D Compute
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Daphne Koller Variable Elimination Goal: P(J) Eliminate: S,L C D I SG L J H D
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Daphne Koller C D I SG L J H D Variable Elimination with evidence Goal: P(J,I=i,H=h) Eliminate: C,D,G,S,L How do we get P(J | I=i,H=h)?
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Daphne Koller Variable Elimination in MNs BD C A Goal: P(D) Eliminate: A,B,C At the end of elimination get 3 (D)
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Daphne Koller Eliminate-Var Z from
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Daphne Koller VE Algorithm Summary Reduce all factors by evidence – Get a set of factors For each non-query variable Z – Eliminate-Var Z from Multiply all remaining factors Renormalize to get distribution
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Daphne Koller Summary Simple algorithm Works for both BNs and MNs Factor product and summation steps can be done in any order, subject to: – when Z is eliminated, all factors involving Z have been multiplied in
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