Mercurial > hg > camir-aes2014
diff toolboxes/FullBNT-1.0.7/bnt/inference/static/@quickscore_inf_engine/quickscore_inf_engine.m @ 0:e9a9cd732c1e tip
first hg version after svn
author | wolffd |
---|---|
date | Tue, 10 Feb 2015 15:05:51 +0000 |
parents | |
children |
line wrap: on
line diff
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/toolboxes/FullBNT-1.0.7/bnt/inference/static/@quickscore_inf_engine/quickscore_inf_engine.m Tue Feb 10 15:05:51 2015 +0000 @@ -0,0 +1,38 @@ +function engine = quickscore_inf_engine(inhibit, leak, prior) +% QUICKSCORE_INF_ENGINE Exact inference for the QMR network +% engine = quickscore_inf_engine(inhibit, leak, prior) +% +% We create an inference engine for QMR-like networks. +% QMR is a bipartite graph, where the top layer contains hidden disease nodes, +% and the bottom later contains observed finding nodes. +% The diseases have Bernoulli CPDs, the findings noisy-or CPDs. +% The original QMR (Quick Medical Reference) network has specific parameter values which we are not +% allowed to release, for commercial reasons. +% +% inhibit(f,d) = inhibition probability on f->d arc for disease d, finding f +% If inhibit(f,d) = 1, there is effectively no arc from d->f +% leak(j) = inhibition prob. on leak node -> finding j arc +% prior(i) = prob. disease i is on +% +% We use exact inference, which takes O(2^P) time, where P is the number of positive findings. +% For details, see +% - Heckerman, "A tractable inference algorithm for diagnosing multiple diseases", UAI 89. +% - Rish and Dechter, "On the impact of causal independence", UCI tech report, 1998. +% Note that this algorithm is numerically unstable, since it adds a large number of positive and +% negative terms and hopes that some of them exactly cancel. +% +% For an interesting variational approximation, see +% - Jaakkola and Jordan, "Variational probabilistic inference and the QMR-DT network", JAIR 10, 1999. +% +% See also +% - "Loopy belief propagation for approximate inference: an empirical study", +% K. Murphy, Y. Weiss and M. Jordan, UAI 99. + +engine.inhibit = inhibit; +engine.leak = leak; +engine.prior = prior; + +% store results here between enter_evidence and marginal_nodes +engine.post = []; + +engine = class(engine, 'quickscore_inf_engine'); % not a child of the inf_engine class!