comparison toolboxes/FullBNT-1.0.7/bnt/examples/static/mpe2.m @ 0:e9a9cd732c1e tip

first hg version after svn

+% Computing most probable explanation.
+
+% If you don't break ties consistently, loopy can give wrong mpe
+% even though the graph has no cycles, and even though the max-marginals are the same.
+% This example was contributed by Wentau Yih <[e-mail]> 29 Jan 02.
+
+% define loop-free graph structure (all edges point down)
+%
+% Xe1   Xe2
+%  |    |
+%  E1   E2
+%    \ /
+%     R1
+%     |
+%    Xr1
+
+N = 6;
+dag = zeros(N,N);
+Xe1 = 1; Xe2 = 2; E1 = 3; E2 = 4; R1 = 5; Xr1 = 6;
+dag(Xe1, E1) = 1;
+dag(Xe2, E2) = 1;
+dag([E1 E2], R1) = 1;
+dag(R1, Xr1) = 1;
+
+node_sizes = [ 1 1 2 2 2 1 ];
+
+% create BN
+
+bnet = mk_bnet(dag, node_sizes, 'observed', [Xe1 Xe2 Xr1]);
+
+% fill in CPT
+
+bnet.CPD{Xe1} = tabular_CPD(bnet, Xe1, [1]);
+bnet.CPD{Xe2} = tabular_CPD(bnet, Xe2, [1]);
+bnet.CPD{E1} = tabular_CPD(bnet, E1, [0.2 0.8]);
+bnet.CPD{E2} = tabular_CPD(bnet, E2, [0.3 0.7]);
+bnet.CPD{R1} = tabular_CPD(bnet, R1, [1 1 1 0.8 0 0 0 0.2]);
+bnet.CPD{Xr1} = tabular_CPD(bnet, Xr1, [0.15 0.85]);
+
+clear engine;
+engine{1} = belprop_inf_engine(bnet);
+engine{2} = jtree_inf_engine(bnet);
+engine{3} = global_joint_inf_engine(bnet);
+engine{4} = var_elim_inf_engine(bnet);
+
+evidence = cell(1,N);
+evidence{Xe1} = 1;  evidence{Xe2} = 1;  evidence{Xr1} = 1;
+
+mpe = find_mpe(engine{1}, evidence, 'break_ties', 0) % gives wrong results
+mpe = find_mpe(engine{1}, evidence)
+for i=2:4
+  mpe = find_mpe(engine{i}, evidence)
+end