wolffd@0: % Evaluate effectiveness of likelihood weighting on the lawn sprinkler example
wolffd@0: 
wolffd@0: N = 4; 
wolffd@0: dag = zeros(N,N);
wolffd@0: C = 1; R = 2; S = 3; W = 4;
wolffd@0: dag(C,[R S]) = 1;
wolffd@0: dag(R,W) = 1;
wolffd@0: dag(S,W)=1;
wolffd@0: 
wolffd@0: false = 1; true = 2;
wolffd@0: ns = 2*ones(1,N); % binary nodes
wolffd@0: 
wolffd@0: bnet = mk_bnet(dag, ns);
wolffd@0: bnet.CPD{C} = tabular_CPD(bnet, C, [0.5 0.5]);
wolffd@0: bnet.CPD{R} = tabular_CPD(bnet, R, [0.8 0.2 0.2 0.8]);
wolffd@0: bnet.CPD{S} = tabular_CPD(bnet, S, [0.5 0.9 0.5 0.1]);
wolffd@0: bnet.CPD{W} = tabular_CPD(bnet, W, [1 0.1 0.1 0.01 0 0.9 0.9 0.99]);
wolffd@0: 
wolffd@0: 
wolffd@0: clear engine;
wolffd@0: engine{1} = jtree_inf_engine(bnet);
wolffd@0: engine{2} = likelihood_weighting_inf_engine(bnet);
wolffd@0: 
wolffd@0: nengines = length(engine);
wolffd@0: m = cell(1, nengines);
wolffd@0: ll = zeros(1, nengines);
wolffd@0: 
wolffd@0: evidence = cell(1,N);
wolffd@0: %evidence{C} = true; % evidence at the top is the easiest
wolffd@0: evidence{W} = true; % evidence at the bottom is the hardets
wolffd@0: 
wolffd@0: query = [R];
wolffd@0: 
wolffd@0: i=1;
wolffd@0: engine{i}  = enter_evidence(engine{i}, evidence);
wolffd@0: exact_m = marginal_nodes(engine{i}, query);
wolffd@0: 
wolffd@0: i=2;
wolffd@0: samples = 100:100:500;
wolffd@0: err = zeros(1, length(samples));
wolffd@0: for j=1:length(samples)
wolffd@0:   nsamples = samples(j);
wolffd@0:   engine{i}  = enter_evidence(engine{i}, evidence, nsamples);
wolffd@0:   approx_m = marginal_nodes(engine{i}, query);
wolffd@0:   a1=approxeq(approx_m.T,exact_m.T,1e-1);
wolffd@0:   a2=approxeq(approx_m.T,exact_m.T,1e-2);
wolffd@0:   a3=approxeq(approx_m.T,exact_m.T,1e-3);
wolffd@0:   e = sum(abs(approx_m.T(:) - exact_m.T(:)));
wolffd@0:   fprintf('%d samples, 1dp %d, 2dp %d, 3dp %d,  err %f\n', nsamples, a1, a2, a3, e);
wolffd@0:   err(j) = e;
wolffd@0: end