comparison toolboxes/FullBNT-1.0.7/bnt/inference/static/@gibbs_sampling_inf_engine/private/get_slice_dbn.m @ 0:e9a9cd732c1e tip

first hg version after svn

+function slice = get_slice_dbn(bnet, state, i, n, j, m, strides, families, ...
+				 CPT)
+% slice = get_slice(bnet, state, i, n, j, m, strides, families, cpt)
+%
+% GET_SLICE get one-dimensional slice of the CPT for node X_i^n
+% that corresponds to the different values of X_j^m, where all
+% other nodes have values given by state.  
+% strides is the result of
+% calling compute_strides(bnet)
+% families is the result of calling compute_families(bnet)
+% cpts is the result of calling get_cpts(bnet)
+%
+% slice is a 1-d array
+
+
+if (n == 1)
+
+  k = bnet.eclass1(i);
+  c = CPT{k};
+  
+  % Figure out evidence on family
+  fam = families{i, 1};
+  ev = state(fam, 1);
+  
+  % Remove evidence on node j
+  pos = find(fam == j);
+  ev(pos) = 1;
+  dim = size(ev, 1);
+  
+  % Compute initial index and stride
+  start_ind = 1+strides(k, 1:dim)*(ev-1);
+  stride = strides(k, pos);
+
+  % Compute the slice
+  slice = c(start_ind:stride:start_ind+(bnet.node_sizes(j, 1)-1)*stride);
+						  
+else
+  
+  k = bnet.eclass2(i);
+  c = CPT{k};
+  
+  fam = families{i, 2};
+  ss = length(bnet.intra);
+  
+  % Divide the family into nodes in this time step and nodes in the
+  % previous time step
+  this_time_step = fam(find(fam > ss));
+  prev_time_step = fam(find(fam <= ss));
+
+  % Normalize the node numbers
+  this_time_step = this_time_step - ss;
+  
+  % Get the evidence
+  this_step_ev = state(this_time_step, n);
+  prev_step_ev = state(prev_time_step, n-1);
+  
+  % Remove the evidence for X_j^m
+  if (m == n)
+    pos = find(this_time_step == j);
+    this_step_ev(pos) = 1;
+    pos = pos + size(prev_time_step, 2);
+  else
+    assert (m == n-1);
+    pos = find(prev_time_step == j);
+    prev_step_ev(pos) = 1;
+  end
+  
+  % Combine the two time steps
+  ev = [prev_step_ev; this_step_ev];
+  dim = size(ev, 1);
+
+
+  % Compute starting index and stride
+  start_ind = 1 + strides(k, 1:dim)*(ev-1);
+  stride = strides(k, pos);
+  
+  % Compute slice 
+  if (m == 1)
+    q = 1;
+  else
+    q = 2;
+  end
+  slice = c(start_ind:stride:start_ind+(bnet.node_sizes(j, q)-1)*stride);
+end
+
+
+