comparison toolboxes/FullBNT-1.0.7/bnt/inference/dynamic/@bk_ff_hmm_inf_engine/private/bk_ff_fb.m @ 0:e9a9cd732c1e tip

first hg version after svn

+function [gamma, loglik, marginals, marginalsT] = bk_ff_fb(prior, transmat, obslik, filter_only, hnodes, ns)
+% BK_FF_FB Fully factored Boyen-Koller version of forwards-backwards
+% [gamma, loglik, marginals, marginalsT] = bk_ff_hmm(prior, transmat, obslik, filter_only, hnodes, ns)
+
+ss  = length(ns);
+S = length(prior);
+T = size(obslik, 2);
+marginals = cell(ss,T);
+marginalsT = cell(ss,T);
+scale = zeros(1,T);
+alpha = zeros(S, T);
+
+transmat2 = transmat';
+for t=1:T
+  if t==1
+    [alpha(:,t), scale(t)] = normalise(prior(:) .* obslik(:,t));
+  else
+    [alpha(:,t), scale(t)] = normalise((transmat2 * alpha(:,t-1)) .* obslik(:,t));
+  end
+  [marginals(:,t), marginalsT(:,t)] = project_joint_onto_marginals(alpha(:,t), hnodes, ns);
+  alpha(:,t) = combine_marginals_into_joint(marginalsT(:,t), hnodes, ns);
+  %fprintf('alpha t=%d\n', t);
+  %celldisp(marginals(1:8,t))
+end
+loglik = sum(log(scale));
+
+if filter_only
+  gamma = alpha;
+  return;
+end
+
+beta = zeros(S,T);
+gamma = zeros(S,T);
+t = T;
+beta(:,t) = ones(S,1);
+gamma(:,t) = normalise(alpha(:,t) .* beta(:,t));
+[marginals(:,t), marginalsT(:,t)] = project_joint_onto_marginals(gamma(:,t), hnodes, ns);
+
+for t=T-1:-1:1
+  b = beta(:,t+1) .* obslik(:,t+1); 
+  beta(:,t) = normalise((transmat * b));
+  [junk, tempT] = project_joint_onto_marginals(beta(:,t), hnodes, ns);
+  beta(:,t) = combine_marginals_into_joint(tempT, hnodes, ns);
+  %gamma(:,t) = normalise(alpha(:,t) .* beta(:,t));
+  %[marginals(:,t), marginalsT(:,t)] = project_joint_onto_marginals(gamma(:,t), hnodes, ns);
+end
+
+gamma2 = zeros(S,T);
+for t=T-1:-1:1
+  b = beta(:,t+1) .* obslik(:,t+1); 
+  xi(:,:,t) = normalise((transmat .* (alpha(:,t) * b')));      
+  if t==T-1
+    gamma2(:,T) = sum(xi(:,:,T-1), 1)';
+  end
+  gamma2(:,t) = sum(xi(:,:,t), 2);
+  [marginals(:,t), marginalsT(:,t)] = project_joint_onto_marginals(gamma2(:,t), hnodes, ns);
+end
+
+