how probability of evidence is calculated

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snowave
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Joined: Mon Jan 25, 2016 1:27 pm

how probability of evidence is calculated

Post by snowave »

Hi, Can I ask how the probability of evidence is calculated in SMILE?
As far as I know, the pe is queried by summing over all possible states which mean the space is exponential. So How Smile does that?
thanks

Peng
shooltz[BayesFusion]
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Posts: 1417
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Re: how probability of evidence is calculated

Post by shooltz[BayesFusion] »

By default SMILE calculates P(e) using jointree-based algorithm; if the jointree resulting from triangulation does not fit into memory, the fallback algorithm based on chain rule is used.

You can force the DSL_network::CalcProbEvidence to use chain rule by passing true as its 2nd argument.
snowave
Posts: 22
Joined: Mon Jan 25, 2016 1:27 pm

Re: how probability of evidence is calculated

Post by snowave »

thanks for the answers.

Can I ask one more question? How to access each probability table associated with each node in the Network? I want to try to calculate the probability of evidence by chain rule but using a subset of all the probability tables.

many thanks

snowave
shooltz[BayesFusion]
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Re: how probability of evidence is calculated

Post by shooltz[BayesFusion] »

How to access each probability table associated with each node in the Network?
Do you mean the conditional probabilities (node definition, stored in xdsl when you save network to disk) or calculated posterior probabilities (node value)?
snowave
Posts: 22
Joined: Mon Jan 25, 2016 1:27 pm

Re: how probability of evidence is calculated

Post by snowave »

yes, I mean the node definition, conditional probability. I think this can be used to calculate the probability of evidence by chain rule.
shooltz[BayesFusion]
Site Admin
Posts: 1417
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Re: how probability of evidence is calculated

Post by shooltz[BayesFusion] »

See the "Anatomy of the node/Node Definition" section in GeNIe manual. Tutorial 3 (Exploring the contents of a model) may also be helpful.
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