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1 function [engine, ll, niter] = enter_evidence(engine, evidence, varargin)
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2 % ENTER_EVIDENCE Propagate evidence using belief propagation
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3 % [engine, ll, niter] = enter_evidence(engine, evidence, ...)
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4 %
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5 % The log-likelihood is not computed; ll = 0.
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6 % niter contains the number of iterations used (if engine.protocol = 'parallel')
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7 %
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8 % The following optional arguments can be specified in the form of name/value pairs:
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9 % [default value in brackets]
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10 %
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11 % maximize - 1 means use max-product, 0 means use sum-product [0]
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12 % exclude - list of nodes whose potential will not be included in the joint [ [] ]
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13 %
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14 % e.g., engine = enter_evidence(engine, ev, 'maximize', 1)
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15
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16 ll = 0;
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17 exclude = [];
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18 maximize = 0;
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19
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20 if nargin >= 3
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21 args = varargin;
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22 nargs = length(args);
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23 for i=1:2:nargs
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24 switch args{i},
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25 case 'exclude', exclude = args{i+1};
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26 case 'maximize', maximize = args{i+1};
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27 otherwise,
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28 error(['invalid argument name ' args{i}]);
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29 end
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30 end
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31 end
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32
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33 engine.maximize = maximize;
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34
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35 if ~isempty(engine.filename)
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36 engine.fid = fopen(engine.filename, 'w');
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37 if engine.fid == 0
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38 error(['can''t open ' engine.filename]);
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39 end
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40 else
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41 engine.fid = [];
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42 end
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43
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44 gdl = engine.gdl;
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45 bnet = bnet_from_engine(engine);
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46
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47 ndoms = length(gdl.doms);
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48 ns = bnet.node_sizes;
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49 onodes = find(~isemptycell(evidence));
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50 pot_type = determine_pot_type(bnet, onodes);
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51
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52 % prime each local kernel with evidence (if any)
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53 local_kernel = cell(1, ndoms);
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54 for i=1:ndoms
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55 if myismember(i, exclude)
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56 local_kernel{i} = mk_initial_pot(pot_type, gdl.doms{i}, ns, bnet.cnodes, onodes);
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57 else
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58 e = bnet.equiv_class(i);
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59 local_kernel{i} = convert_to_pot(bnet.CPD{e}, pot_type, gdl.doms{i}(:), evidence);
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60 end
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61 end
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62
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63 % initialise all msgs to 1s
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64 msg = cell(ndoms, ndoms);
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65 for i=1:ndoms
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66 nbrs = gdl.nbrs{i};
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67 for j=nbrs(:)'
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68 dom = gdl.sepset{i,j};
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69 msg{i,j} = mk_initial_pot(pot_type, dom, ns, bnet.cnodes, onodes);
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70 end
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71 end
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72
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73 switch engine.protocol
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74 case 'parallel',
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75 [engine.marginal_domains, niter] = parallel_protocol(engine, evidence, pot_type, local_kernel, msg);
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76 case 'tree',
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77 engine.marginal_domains = serial_protocol(engine, evidence, pot_type, local_kernel, msg);
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78 niter = 1;
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79 end
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80 engine.niter = niter;
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81
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82 %fprintf('just finished %d iterations of belprop\n', niter);
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83
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84 if ~isempty(engine.filename)
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85 fclose(engine.fid);
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86 end
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