comparison toolboxes/FullBNT-1.0.7/bnt/general/Old/calc_mpe.m @ 0:e9a9cd732c1e tip

first hg version after svn

+function [mpe, ll] = calc_mpe(engine, evidence, break_ties)
+% CALC_MPE Computes the most probable explanation of the evidence
+% [mpe, ll] = calc_mpe_given_inf_engine(engine, evidence, break_ties)
+%
+% INPUT
+% engine must support max-propagation
+% evidence{i} is the observed value of node i, or [] if hidden
+% break_ties is optional. If 1, we will force ties to be broken consistently
+%  by calling enter_evidence N times.
+%
+% OUTPUT
+% mpe{i} is the most likely value of node i (cell array!)
+% ll is the log-likelihood of the globally best assignment
+%
+% This currently only works when all hidden nodes are discrete
+
+if nargin < 3, break_ties = 0; end
+
+
+[engine, ll] = enter_evidence(engine, evidence, 'maximize', 1);
+
+observed = ~isemptycell(evidence);
+
+if 0 % fgraphs don't support bnet_from_engine
+onodes = find(observed);
+bnet = bnet_from_engine(engine);
+pot_type = determine_pot_type(bnet, onodes);
+assert(pot_type == 'd');
+end
+
+scalar = 1;
+evidence = evidence(:); % hack to handle unrolled DBNs
+N = length(evidence);
+mpe = cell(1,N);
+for i=1:N
+  m = marginal_nodes(engine, i);
+  % observed nodes are all set to 1 inside the inference engine, so we must undo this
+  if observed(i)
+    mpe{i} = evidence{i};
+  else
+    mpe{i} = argmax(m.T);
+    % Bug fix by Ron Zohar, 8/15/01
+    % If there are ties, we must break them as follows (see Jensen96, p106)
+    if break_ties
+      evidence{i} = mpe{i};                             
+      [engine, ll] = enter_evidence(engine, evidence, 'maximize', 1);  
+    end
+  end
+  if length(mpe{i}) > 1, scalar = 0; end
+end
+
+if nargout >= 2
+  bnet = bnet_from_engine(engine);
+  ll = log_lik_complete(bnet, mpe(:));
+end
+if 0 % scalar
+  mpe = cell2num(mpe);
+end