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1 function engine = belprop_gdl_inf_engine(gdl, varargin)
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2 % BELPROP_GDL_INF_ENGINE Make a belief propagation inference engine for a GDL graph
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3 % engine = belprop_gdl_inf_engine(gdl_graph, ...)
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4 %
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5 % If the GDL graph is a tree, this will give exact results.
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6 %
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7 % The following optional arguments can be specified in the form of name/value pairs:
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8 % [default in brackets]
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9 % e.g., engine = belprop_inf_engine(gdl, 'tol', 1e-2, 'max_iter', 10)
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10 %
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11 % protocol - 'tree' means send messages up then down the tree,
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12 % 'parallel' means use synchronous updates ['parallel']
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13 % max_iter - max. num. iterations [ 2*num_nodes ]
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14 % momentum - weight assigned to old message in convex combination (useful for damping oscillations) [0]
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15 % tol - tolerance used to assess convergence [1e-3]
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16 % maximize - 1 means use max-product, 0 means use sum-product [0]
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17
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18
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19 engine = init_fields;
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20 engine = class(engine, 'belprop_gdl_inf_engine');
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21
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22 % set default params
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23 N = length(gdl.G);
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24 engine.protocol = 'parallel';
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25 engine.max_iter = 2*N;
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26 engine.momentum = 0;
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27 engine.tol = 1e-3;
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28 engine.maximize = 0;
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29
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30 engine = set_params(engine, varargin);
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31
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32 engine.gdl = gdl;
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33
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34 if strcmp(engine.protocol, 'tree')
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35 % Make a rooted tree, so there is a fixed message passing order.
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36 root = N;
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37 [engine.tree, engine.preorder, engine.postorder, height, cyclic] = mk_rooted_tree(gdl.G, root);
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38 assert(~cyclic);
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39 end
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40
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41 % store results computed by enter_evidence here
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42 ndoms = length(gdl.doms);
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43 nvars = length(gdl.vars);
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44 engine.marginal_domains = cell(1, ndoms);
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45
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46 % to compute the marginal on each variable, we need to know which domain to marginalize
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47 % and we want to choose the lightest. We compute the weight once we have seen the evidence.
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48 engine.dom_weight = [];
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49 engine.evidence = [];
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50
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51
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52 %%%%%%%%%
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53
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54 function engine = init_fields()
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55
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56 engine.protocol = [];
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57 engine.gdl = [];
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58 engine.max_iter = [];
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59 engine.momentum = [];
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60 engine.tol = [];
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61 engine.maximize = [];
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62 engine.marginal_domains = [];
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63 engine.evidence = [];
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64 engine.tree = [];
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65 engine.preorder = [];
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66 engine.postorder = [];
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67 engine.dom_weight = [];
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